diff --git a/.bazelversion b/.bazelversion
index 25939d3..3eefcb9 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-0.29.1
+1.0.0
diff --git a/Documentation/user-request-tracing.txt b/Documentation/user-request-tracing.txt
index d422dd9..b26f4c1 100644
--- a/Documentation/user-request-tracing.txt
+++ b/Documentation/user-request-tracing.txt
@@ -22,12 +22,19 @@
   `--trace` option. More information about this can be found in
   the link:cmd-index.html#trace[Trace] section of the
   link:cmd-index.html[SSH command documentation].
-* Git: For Git pushes tracing can be enabled by setting the
-  `trace` push option, the trace ID is returned in the command output.
-  More information about this can be found in
-  the link:user-upload.html#trace[Trace] section of the
-  link:user-upload.html[upload documentation]. Tracing for Git requests
-  other than Git push is not supported.
+* Git Push (requires usage of git protocol v2): For Git pushes tracing
+  can be enabled by setting the `trace` push option, the trace ID is
+  returned in the command output. More information about this can be
+  found in the link:user-upload.html#trace[Trace] section of the
+  link:user-upload.html[upload documentation].
+* Git Clone/Fetch/Ls-Remote (requires usage of git protocol v2): For
+  Git clone/fetch/ls-remote tracing can be enabled by setting the
+  `trace` server option. Use '-o trace=<TRACE-ID>' for `git fetch` and
+  `git ls-remote`, and '--server-option trace=<TRACE-ID>' for
+  `git clone`. If the `trace` server option is set without a value
+  (without trace ID) a trace ID is generated but the generated trace ID
+  is not returned to the client (hence a trace ID should always be
+  set).
 
 When request tracing is enabled it is possible to provide an ID that
 should be used as trace ID. If a trace ID is not provided a trace ID is
diff --git a/WORKSPACE b/WORKSPACE
index 7b843b6..0d54bbe 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -611,18 +611,18 @@
     sha1 = "18d4d07010c24405129a6dbb0e92057f8779fb9d",
 )
 
-AUTO_VALUE_VERSION = "1.6.6"
+AUTO_VALUE_VERSION = "1.7"
 
 maven_jar(
     name = "auto-value",
     artifact = "com.google.auto.value:auto-value:" + AUTO_VALUE_VERSION,
-    sha1 = "8831874cb2f4a9e1b196a2973f3cef695f5ce459",
+    sha1 = "fe8387764ed19460eda4f106849c664f51c07121",
 )
 
 maven_jar(
     name = "auto-value-annotations",
     artifact = "com.google.auto.value:auto-value-annotations:" + AUTO_VALUE_VERSION,
-    sha1 = "9947ae63d8ec42ea159283baf2e5b9c0ff100909",
+    sha1 = "5be124948ebdc7807df68207f35a0f23ce427f29",
 )
 
 declare_nongoogle_deps()
@@ -743,8 +743,8 @@
 # Keep this version of Soy synchronized with the version used in Gitiles.
 maven_jar(
     name = "soy",
-    artifact = "com.google.template:soy:2019-09-03",
-    sha1 = "40781da0302b4b5d53006dc8bd5a432c7288d807",
+    artifact = "com.google.template:soy:2019-10-08",
+    sha1 = "4518bf8bac2dbbed684849bc209c39c4cb546237",
 )
 
 maven_jar(
diff --git a/java/com/google/gerrit/acceptance/ExtensionRegistry.java b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
index c3823cd..f9116a1 100644
--- a/java/com/google/gerrit/acceptance/ExtensionRegistry.java
+++ b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
@@ -16,20 +16,29 @@
 
 import com.google.gerrit.extensions.api.changes.ActionVisitor;
 import com.google.gerrit.extensions.config.DownloadScheme;
+import com.google.gerrit.extensions.events.AccountIndexedListener;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
 import com.google.gerrit.extensions.events.CommentAddedListener;
+import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
+import com.google.gerrit.extensions.events.GroupIndexedListener;
 import com.google.gerrit.extensions.events.ProjectIndexedListener;
+import com.google.gerrit.extensions.events.RevisionCreatedListener;
 import com.google.gerrit.extensions.registration.DynamicMap;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.registration.PrivateInternals_DynamicMapImpl;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
+import com.google.gerrit.extensions.webui.FileHistoryWebLink;
+import com.google.gerrit.extensions.webui.PatchSetWebLink;
 import com.google.gerrit.server.ExceptionHook;
+import com.google.gerrit.server.account.GroupBackend;
 import com.google.gerrit.server.change.ChangeETagComputation;
 import com.google.gerrit.server.git.ChangeMessageModifier;
 import com.google.gerrit.server.git.validators.CommitValidationListener;
+import com.google.gerrit.server.git.validators.OnSubmitValidationListener;
 import com.google.gerrit.server.git.validators.RefOperationValidationListener;
 import com.google.gerrit.server.logging.PerformanceLogger;
 import com.google.gerrit.server.rules.SubmitRule;
+import com.google.gerrit.server.validators.AccountActivationValidationListener;
 import com.google.gerrit.server.validators.ProjectCreationValidationListener;
 import com.google.inject.Inject;
 import com.google.inject.util.Providers;
@@ -37,7 +46,9 @@
 import java.util.List;
 
 public class ExtensionRegistry {
+  private final DynamicSet<AccountIndexedListener> accountIndexedListeners;
   private final DynamicSet<ChangeIndexedListener> changeIndexedListeners;
+  private final DynamicSet<GroupIndexedListener> groupIndexedListeners;
   private final DynamicSet<ProjectIndexedListener> projectIndexedListeners;
   private final DynamicSet<CommitValidationListener> commitValidationListeners;
   private final DynamicSet<ExceptionHook> exceptionHooks;
@@ -50,10 +61,20 @@
   private final DynamicMap<DownloadScheme> downloadSchemes;
   private final DynamicSet<RefOperationValidationListener> refOperationValidationListeners;
   private final DynamicSet<CommentAddedListener> commentAddedListeners;
+  private final DynamicSet<GitReferenceUpdatedListener> refUpdatedListeners;
+  private final DynamicSet<FileHistoryWebLink> fileHistoryWebLinks;
+  private final DynamicSet<PatchSetWebLink> patchSetWebLinks;
+  private final DynamicSet<RevisionCreatedListener> revisionCreatedListeners;
+  private final DynamicSet<GroupBackend> groupBackends;
+  private final DynamicSet<AccountActivationValidationListener>
+      accountActivationValidationListeners;
+  private final DynamicSet<OnSubmitValidationListener> onSubmitValidationListeners;
 
   @Inject
   ExtensionRegistry(
+      DynamicSet<AccountIndexedListener> accountIndexedListeners,
       DynamicSet<ChangeIndexedListener> changeIndexedListeners,
+      DynamicSet<GroupIndexedListener> groupIndexedListeners,
       DynamicSet<ProjectIndexedListener> projectIndexedListeners,
       DynamicSet<CommitValidationListener> commitValidationListeners,
       DynamicSet<ExceptionHook> exceptionHooks,
@@ -65,8 +86,17 @@
       DynamicSet<ActionVisitor> actionVisitors,
       DynamicMap<DownloadScheme> downloadSchemes,
       DynamicSet<RefOperationValidationListener> refOperationValidationListeners,
-      DynamicSet<CommentAddedListener> commentAddedListeners) {
+      DynamicSet<CommentAddedListener> commentAddedListeners,
+      DynamicSet<GitReferenceUpdatedListener> refUpdatedListeners,
+      DynamicSet<FileHistoryWebLink> fileHistoryWebLinks,
+      DynamicSet<PatchSetWebLink> patchSetWebLinks,
+      DynamicSet<RevisionCreatedListener> revisionCreatedListeners,
+      DynamicSet<GroupBackend> groupBackends,
+      DynamicSet<AccountActivationValidationListener> accountActivationValidationListeners,
+      DynamicSet<OnSubmitValidationListener> onSubmitValidationListeners) {
+    this.accountIndexedListeners = accountIndexedListeners;
     this.changeIndexedListeners = changeIndexedListeners;
+    this.groupIndexedListeners = groupIndexedListeners;
     this.projectIndexedListeners = projectIndexedListeners;
     this.commitValidationListeners = commitValidationListeners;
     this.exceptionHooks = exceptionHooks;
@@ -79,19 +109,35 @@
     this.downloadSchemes = downloadSchemes;
     this.refOperationValidationListeners = refOperationValidationListeners;
     this.commentAddedListeners = commentAddedListeners;
+    this.refUpdatedListeners = refUpdatedListeners;
+    this.fileHistoryWebLinks = fileHistoryWebLinks;
+    this.patchSetWebLinks = patchSetWebLinks;
+    this.revisionCreatedListeners = revisionCreatedListeners;
+    this.groupBackends = groupBackends;
+    this.accountActivationValidationListeners = accountActivationValidationListeners;
+    this.onSubmitValidationListeners = onSubmitValidationListeners;
   }
 
   public Registration newRegistration() {
     return new Registration();
   }
 
+  @SuppressWarnings("FunctionalInterfaceClash")
   public class Registration implements AutoCloseable {
     private final List<RegistrationHandle> registrationHandles = new ArrayList<>();
 
+    public Registration add(AccountIndexedListener accountIndexedListener) {
+      return add(accountIndexedListeners, accountIndexedListener);
+    }
+
     public Registration add(ChangeIndexedListener changeIndexedListener) {
       return add(changeIndexedListeners, changeIndexedListener);
     }
 
+    public Registration add(GroupIndexedListener groupIndexedListener) {
+      return add(groupIndexedListeners, groupIndexedListener);
+    }
+
     public Registration add(ProjectIndexedListener projectIndexedListener) {
       return add(projectIndexedListeners, projectIndexedListener);
     }
@@ -120,6 +166,10 @@
       return add(changeMessageModifiers, changeMessageModifier);
     }
 
+    public Registration add(ChangeMessageModifier changeMessageModifier, String exportName) {
+      return add(changeMessageModifiers, changeMessageModifier, exportName);
+    }
+
     public Registration add(ChangeETagComputation changeETagComputation) {
       return add(changeETagComputations, changeETagComputation);
     }
@@ -140,8 +190,41 @@
       return add(commentAddedListeners, commentAddedListener);
     }
 
+    public Registration add(GitReferenceUpdatedListener refUpdatedListener) {
+      return add(refUpdatedListeners, refUpdatedListener);
+    }
+
+    public Registration add(FileHistoryWebLink fileHistoryWebLink) {
+      return add(fileHistoryWebLinks, fileHistoryWebLink);
+    }
+
+    public Registration add(PatchSetWebLink patchSetWebLink) {
+      return add(patchSetWebLinks, patchSetWebLink);
+    }
+
+    public Registration add(RevisionCreatedListener revisionCreatedListener) {
+      return add(revisionCreatedListeners, revisionCreatedListener);
+    }
+
+    public Registration add(GroupBackend groupBackend) {
+      return add(groupBackends, groupBackend);
+    }
+
+    public Registration add(
+        AccountActivationValidationListener accountActivationValidationListener) {
+      return add(accountActivationValidationListeners, accountActivationValidationListener);
+    }
+
+    public Registration add(OnSubmitValidationListener onSubmitValidationListener) {
+      return add(onSubmitValidationListeners, onSubmitValidationListener);
+    }
+
     private <T> Registration add(DynamicSet<T> dynamicSet, T extension) {
-      RegistrationHandle registrationHandle = dynamicSet.add("gerrit", extension);
+      return add(dynamicSet, extension, "gerrit");
+    }
+
+    private <T> Registration add(DynamicSet<T> dynamicSet, T extension, String exportname) {
+      RegistrationHandle registrationHandle = dynamicSet.add(exportname, extension);
       registrationHandles.add(registrationHandle);
       return this;
     }
diff --git a/java/com/google/gerrit/acceptance/GitClientVersion.java b/java/com/google/gerrit/acceptance/GitClientVersion.java
new file mode 100644
index 0000000..4c9a32d
--- /dev/null
+++ b/java/com/google/gerrit/acceptance/GitClientVersion.java
@@ -0,0 +1,66 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance;
+
+import static java.util.stream.Collectors.joining;
+
+import java.util.stream.IntStream;
+
+/** Class to parse and represent version of git-core client */
+public class GitClientVersion implements Comparable<GitClientVersion> {
+  private final int v[];
+
+  /**
+   * Constructor to represent instance for minimum supported git-core version
+   *
+   * @param parts version passed as single digits
+   */
+  public GitClientVersion(int... parts) {
+    this.v = parts;
+  }
+
+  /**
+   * Parse the git-core version as returned by git version command
+   *
+   * @param version String returned by git version command
+   */
+  public GitClientVersion(String version) {
+    // "git version x.y.z", at Google "git version x.y.z.gXXXXXXXXXX-goog"
+    String parts[] = version.split(" ")[2].split("\\.");
+    int numParts = Math.min(parts.length, 3); // ignore Google-specific part of the version
+    v = new int[numParts];
+    for (int i = 0; i < numParts; i++) {
+      v[i] = Integer.valueOf(parts[i]);
+    }
+  }
+
+  @Override
+  public int compareTo(GitClientVersion o) {
+    int m = Math.max(v.length, o.v.length);
+    for (int i = 0; i < m; i++) {
+      int l = i < v.length ? v[i] : 0;
+      int r = i < o.v.length ? o.v[i] : 0;
+      if (l != r) {
+        return l < r ? -1 : 1;
+      }
+    }
+    return 0;
+  }
+
+  @Override
+  public String toString() {
+    return IntStream.of(v).mapToObj(String::valueOf).collect(joining("."));
+  }
+}
diff --git a/java/com/google/gerrit/acceptance/StandaloneSiteTest.java b/java/com/google/gerrit/acceptance/StandaloneSiteTest.java
index 933c4e1..a095daa 100644
--- a/java/com/google/gerrit/acceptance/StandaloneSiteTest.java
+++ b/java/com/google/gerrit/acceptance/StandaloneSiteTest.java
@@ -15,16 +15,20 @@
 package com.google.gerrit.acceptance;
 
 import static com.google.common.truth.Truth.assertWithMessage;
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.stream.Collectors.joining;
 import static org.junit.Assert.fail;
 
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Streams;
+import com.google.common.io.ByteStreams;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.api.GerritApi;
 import com.google.gerrit.extensions.api.groups.GroupInput;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.launcher.GerritLauncher;
-import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.config.SitePaths;
 import com.google.gerrit.server.util.ManualRequestContext;
@@ -35,6 +39,9 @@
 import com.google.inject.Injector;
 import com.google.inject.Module;
 import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InterruptedIOException;
 import java.util.Arrays;
 import java.util.Collections;
 import org.eclipse.jgit.lib.Config;
@@ -59,10 +66,10 @@
     private ServerContext(GerritServer server) throws Exception {
       this.server = server;
       Injector i = server.getTestInjector();
-      if (adminId == null) {
-        adminId = i.getInstance(AccountCreator.class).admin().id();
+      if (admin == null) {
+        admin = i.getInstance(AccountCreator.class).admin();
       }
-      ctx = i.getInstance(OneOffRequestContext.class).openAs(adminId);
+      ctx = i.getInstance(OneOffRequestContext.class).openAs(admin.id());
       GerritApi gApi = i.getInstance(GerritApi.class);
 
       try {
@@ -117,7 +124,7 @@
   @Rule public RuleChain ruleChain = RuleChain.outerRule(tempSiteDir).around(testRunner);
 
   protected SitePaths sitePaths;
-  protected Account.Id adminId;
+  protected TestAccount admin;
 
   private GerritServer.Description serverDesc;
   private SystemReader oldSystemReader;
@@ -190,4 +197,33 @@
   protected static void runGerrit(Iterable<String>... multiArgs) throws Exception {
     runGerrit(Arrays.stream(multiArgs).flatMap(Streams::stream).toArray(String[]::new));
   }
+
+  protected static String execute(
+      ImmutableList<String> cmd, File dir, ImmutableMap<String, String> env) throws IOException {
+    ProcessBuilder pb = new ProcessBuilder(cmd);
+    pb.directory(dir).redirectErrorStream(true);
+    pb.environment().putAll(env);
+    Process p = pb.start();
+    byte[] out;
+    try (InputStream in = p.getInputStream()) {
+      out = ByteStreams.toByteArray(in);
+    } finally {
+      p.getOutputStream().close();
+    }
+
+    int status;
+    try {
+      status = p.waitFor();
+    } catch (InterruptedException e) {
+      throw new InterruptedIOException(
+          "interrupted waiting for: " + Joiner.on(' ').join(pb.command()));
+    }
+
+    String result = new String(out, UTF_8);
+    if (status != 0) {
+      throw new IOException(result);
+    }
+
+    return result.trim();
+  }
 }
diff --git a/java/com/google/gerrit/httpd/GitOverHttpServlet.java b/java/com/google/gerrit/httpd/GitOverHttpServlet.java
index ff2a83d..858c173 100644
--- a/java/com/google/gerrit/httpd/GitOverHttpServlet.java
+++ b/java/com/google/gerrit/httpd/GitOverHttpServlet.java
@@ -32,6 +32,7 @@
 import com.google.gerrit.server.cache.CacheModule;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.PermissionAwareRepositoryManager;
+import com.google.gerrit.server.git.TracingHook;
 import com.google.gerrit.server.git.TransferConfig;
 import com.google.gerrit.server.git.UploadPackInitializer;
 import com.google.gerrit.server.git.receive.AsyncReceiveCommits;
@@ -415,7 +416,11 @@
         up.setPreUploadHook(
             PreUploadHookChain.newChain(
                 Lists.newArrayList(up.getPreUploadHook(), uploadValidators)));
-        next.doFilter(httpRequest, responseWrapper);
+
+        try (TracingHook tracingHook = new TracingHook()) {
+          up.setProtocolV2Hook(tracingHook);
+          next.doFilter(httpRequest, responseWrapper);
+        }
       } finally {
         groupAuditService.dispatch(
             new HttpAuditEvent(
diff --git a/java/com/google/gerrit/index/query/QueryProcessor.java b/java/com/google/gerrit/index/query/QueryProcessor.java
index 61d609b..9501e52 100644
--- a/java/com/google/gerrit/index/query/QueryProcessor.java
+++ b/java/com/google/gerrit/index/query/QueryProcessor.java
@@ -218,7 +218,7 @@
 
     logger.atFine().log(
         "Executing %d %s index queries for %s",
-        cnt, schemaDef.getName(), callerFinder.findCaller());
+        cnt, schemaDef.getName(), callerFinder.findCallerLazy());
     List<QueryResult<T>> out;
     try {
       // Parse and rewrite all queries.
diff --git a/java/com/google/gerrit/server/account/externalids/ExternalIdNotes.java b/java/com/google/gerrit/server/account/externalids/ExternalIdNotes.java
index 2c72f56..d75aa17 100644
--- a/java/com/google/gerrit/server/account/externalids/ExternalIdNotes.java
+++ b/java/com/google/gerrit/server/account/externalids/ExternalIdNotes.java
@@ -675,7 +675,8 @@
   @Override
   protected void onLoad() throws IOException, ConfigInvalidException {
     if (revision != null) {
-      logger.atFine().log("Reading external ID note map (caller: %s)", callerFinder.findCaller());
+      logger.atFine().log(
+          "Reading external ID note map (caller: %s)", callerFinder.findCallerLazy());
       noteMap = NoteMap.read(reader, revision);
     } else {
       noteMap = NoteMap.newEmptyMap();
diff --git a/java/com/google/gerrit/server/change/testing/TestChangeETagComputation.java b/java/com/google/gerrit/server/change/testing/TestChangeETagComputation.java
new file mode 100644
index 0000000..344b9b3
--- /dev/null
+++ b/java/com/google/gerrit/server/change/testing/TestChangeETagComputation.java
@@ -0,0 +1,30 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change.testing;
+
+import com.google.gerrit.server.change.ChangeETagComputation;
+
+public class TestChangeETagComputation {
+
+  public static ChangeETagComputation withETag(String etag) {
+    return (p, id) -> etag;
+  }
+
+  public static ChangeETagComputation withException(RuntimeException e) {
+    return (p, id) -> {
+      throw e;
+    };
+  }
+}
diff --git a/java/com/google/gerrit/server/git/TracingHook.java b/java/com/google/gerrit/server/git/TracingHook.java
new file mode 100644
index 0000000..4191373
--- /dev/null
+++ b/java/com/google/gerrit/server/git/TracingHook.java
@@ -0,0 +1,99 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.git;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.common.collect.Iterables;
+import com.google.common.collect.LinkedListMultimap;
+import com.google.common.collect.ListMultimap;
+import com.google.gerrit.server.logging.TraceContext;
+import java.util.List;
+import java.util.Optional;
+import org.eclipse.jgit.transport.FetchV2Request;
+import org.eclipse.jgit.transport.LsRefsV2Request;
+import org.eclipse.jgit.transport.ProtocolV2Hook;
+
+/**
+ * Git hook for ls-refs and fetch that enables Gerrit request tracing if the user sets the 'trace'
+ * server option.
+ *
+ * <p>This hook is only invoked if Git protocol v2 is used.
+ *
+ * <p>If the 'trace' server option is specified without value, this means without providing a trace
+ * ID, a trace ID is generated, but it's not returned to the client. Hence users are advised to
+ * always provide a trace ID.
+ */
+public class TracingHook implements ProtocolV2Hook, AutoCloseable {
+  private TraceContext traceContext;
+
+  @Override
+  public void onLsRefs(LsRefsV2Request req) {
+    maybeStartTrace(req.getServerOptions());
+  }
+
+  @Override
+  public void onFetch(FetchV2Request req) {
+    maybeStartTrace(req.getServerOptions());
+  }
+
+  @Override
+  public void close() {
+    if (traceContext != null) {
+      traceContext.close();
+    }
+  }
+
+  /**
+   * Starts request tracing if 'trace' server option is set.
+   *
+   * @param serverOptionList list of provided server options
+   */
+  private void maybeStartTrace(List<String> serverOptionList) {
+    checkState(traceContext == null, "Trace was already started.");
+
+    Optional<String> traceOption = parseTraceOption(serverOptionList);
+    traceContext =
+        TraceContext.newTrace(
+            traceOption.isPresent(),
+            traceOption.orElse(null),
+            (tagName, traceId) -> {
+              // TODO(ekempin): Return trace ID to client
+            });
+  }
+
+  private Optional<String> parseTraceOption(List<String> serverOptionList) {
+    if (serverOptionList == null || serverOptionList.isEmpty()) {
+      return Optional.empty();
+    }
+
+    ListMultimap<String, String> serverOptions = LinkedListMultimap.create();
+    for (String option : serverOptionList) {
+      int e = option.indexOf('=');
+      if (e > 0) {
+        serverOptions.put(option.substring(0, e), option.substring(e + 1));
+      } else {
+        serverOptions.put(option, "");
+      }
+    }
+
+    List<String> traceValues = serverOptions.get("trace");
+    if (!traceValues.isEmpty()) {
+      return Optional.of(Iterables.getLast(traceValues));
+    }
+
+    return Optional.empty();
+  }
+}
diff --git a/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java b/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java
index 2706eaa..ef008a1 100644
--- a/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java
+++ b/java/com/google/gerrit/server/git/receive/BranchCommitValidator.java
@@ -29,6 +29,8 @@
 import com.google.gerrit.server.git.validators.CommitValidationException;
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
 import com.google.gerrit.server.git.validators.CommitValidators;
+import com.google.gerrit.server.logging.TraceContext;
+import com.google.gerrit.server.logging.TraceContext.TraceTimer;
 import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.ssh.SshInfo;
@@ -130,44 +132,48 @@
       @Nullable Change change,
       boolean skipValidation)
       throws IOException {
-    ImmutableList.Builder<CommitValidationMessage> messages = new ImmutableList.Builder<>();
-    try (CommitReceivedEvent receiveEvent =
-        new CommitReceivedEvent(cmd, project, branch.branch(), objectReader, commit, user)) {
-      CommitValidators validators;
-      if (isMerged) {
-        validators =
-            commitValidatorsFactory.forMergedCommits(permissions, branch, user.asIdentifiedUser());
-      } else {
-        validators =
-            commitValidatorsFactory.forReceiveCommits(
-                permissions,
-                branch,
-                user.asIdentifiedUser(),
-                sshInfo,
-                rejectCommits,
-                receiveEvent.revWalk,
-                change,
-                skipValidation);
-      }
+    try (TraceTimer traceTimer = TraceContext.newTimer("BranchCommitValidator#validateCommit")) {
+      ImmutableList.Builder<CommitValidationMessage> messages = new ImmutableList.Builder<>();
+      try (CommitReceivedEvent receiveEvent =
+          new CommitReceivedEvent(cmd, project, branch.branch(), objectReader, commit, user)) {
+        CommitValidators validators;
+        if (isMerged) {
+          validators =
+              commitValidatorsFactory.forMergedCommits(
+                  permissions, branch, user.asIdentifiedUser());
+        } else {
+          validators =
+              commitValidatorsFactory.forReceiveCommits(
+                  permissions,
+                  branch,
+                  user.asIdentifiedUser(),
+                  sshInfo,
+                  rejectCommits,
+                  receiveEvent.revWalk,
+                  change,
+                  skipValidation);
+        }
 
-      for (CommitValidationMessage m : validators.validate(receiveEvent)) {
-        messages.add(
-            new CommitValidationMessage(
-                messageForCommit(commit, m.getMessage(), objectReader), m.getType()));
+        for (CommitValidationMessage m : validators.validate(receiveEvent)) {
+          messages.add(
+              new CommitValidationMessage(
+                  messageForCommit(commit, m.getMessage(), objectReader), m.getType()));
+        }
+      } catch (CommitValidationException e) {
+        logger.atFine().log("Commit validation failed on %s", commit.name());
+        for (CommitValidationMessage m : e.getMessages()) {
+          // The non-error messages may contain background explanation for the
+          // fatal error, so have to preserve all messages.
+          messages.add(
+              new CommitValidationMessage(
+                  messageForCommit(commit, m.getMessage(), objectReader), m.getType()));
+        }
+        cmd.setResult(
+            REJECTED_OTHER_REASON, messageForCommit(commit, e.getMessage(), objectReader));
+        return Result.create(false, messages.build());
       }
-    } catch (CommitValidationException e) {
-      logger.atFine().log("Commit validation failed on %s", commit.name());
-      for (CommitValidationMessage m : e.getMessages()) {
-        // The non-error messages may contain background explanation for the
-        // fatal error, so have to preserve all messages.
-        messages.add(
-            new CommitValidationMessage(
-                messageForCommit(commit, m.getMessage(), objectReader), m.getType()));
-      }
-      cmd.setResult(REJECTED_OTHER_REASON, messageForCommit(commit, e.getMessage(), objectReader));
-      return Result.create(false, messages.build());
+      return Result.create(true, messages.build());
     }
-    return Result.create(true, messages.build());
   }
 
   private String messageForCommit(RevCommit c, String msg, ObjectReader objectReader)
diff --git a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
index ef782d1..07bbade 100644
--- a/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
+++ b/java/com/google/gerrit/server/git/receive/ReceiveCommits.java
@@ -2002,45 +2002,48 @@
    */
   private boolean requestReplaceAndValidateComments(
       ReceiveCommand cmd, boolean checkMergedInto, Change change, RevCommit newCommit) {
-    if (change.isClosed()) {
-      reject(
-          cmd,
-          changeFormatter.changeClosed(
-              ChangeReportFormatter.Input.builder().setChange(change).build()));
-      return false;
-    }
+    try (TraceTimer traceTimer = newTimer("requestReplaceAndValidateComments")) {
+      if (change.isClosed()) {
+        reject(
+            cmd,
+            changeFormatter.changeClosed(
+                ChangeReportFormatter.Input.builder().setChange(change).build()));
+        return false;
+      }
 
-    ReplaceRequest req = new ReplaceRequest(change.getId(), newCommit, cmd, checkMergedInto);
-    if (replaceByChange.containsKey(req.ontoChange)) {
-      reject(cmd, "duplicate request");
-      return false;
-    }
+      ReplaceRequest req = new ReplaceRequest(change.getId(), newCommit, cmd, checkMergedInto);
+      if (replaceByChange.containsKey(req.ontoChange)) {
+        reject(cmd, "duplicate request");
+        return false;
+      }
 
-    if (magicBranch != null && magicBranch.shouldPublishComments()) {
-      List<Comment> drafts =
-          commentsUtil.draftByChangeAuthor(notesFactory.createChecked(change), user.getAccountId());
-      ImmutableList<CommentForValidation> draftsForValidation =
-          drafts.stream()
-              .map(
-                  comment ->
-                      CommentForValidation.create(
-                          comment.lineNbr > 0
-                              ? CommentType.INLINE_COMMENT
-                              : CommentType.FILE_COMMENT,
-                          comment.message))
-              .collect(toImmutableList());
-      ImmutableList<CommentValidationFailure> commentValidationFailures =
-          PublishCommentUtil.findInvalidComments(commentValidators, draftsForValidation);
-      magicBranch.setCommentsValid(commentValidationFailures.isEmpty());
-      commentValidationFailures.forEach(
-          failure ->
-              addMessage(
-                  "Comment validation failure: " + failure.getMessage(),
-                  ValidationMessage.Type.WARNING));
-    }
+      if (magicBranch != null && magicBranch.shouldPublishComments()) {
+        List<Comment> drafts =
+            commentsUtil.draftByChangeAuthor(
+                notesFactory.createChecked(change), user.getAccountId());
+        ImmutableList<CommentForValidation> draftsForValidation =
+            drafts.stream()
+                .map(
+                    comment ->
+                        CommentForValidation.create(
+                            comment.lineNbr > 0
+                                ? CommentType.INLINE_COMMENT
+                                : CommentType.FILE_COMMENT,
+                            comment.message))
+                .collect(toImmutableList());
+        ImmutableList<CommentValidationFailure> commentValidationFailures =
+            PublishCommentUtil.findInvalidComments(commentValidators, draftsForValidation);
+        magicBranch.setCommentsValid(commentValidationFailures.isEmpty());
+        commentValidationFailures.forEach(
+            failure ->
+                addMessage(
+                    "Comment validation failure: " + failure.getMessage(),
+                    ValidationMessage.Type.WARNING));
+      }
 
-    replaceByChange.put(req.ontoChange, req);
-    return true;
+      replaceByChange.put(req.ontoChange, req);
+      return true;
+    }
   }
 
   private void warnAboutMissingChangeId(List<CreateRequest> newChanges) {
@@ -2333,19 +2336,21 @@
   }
 
   private boolean foundInExistingRef(Collection<Ref> existingRefs) {
-    for (Ref ref : existingRefs) {
-      ChangeNotes notes =
-          notesFactory.create(project.getNameKey(), Change.Id.fromRef(ref.getName()));
-      Change change = notes.getChange();
-      if (change.getDest().equals(magicBranch.dest)) {
-        logger.atFine().log("Found change %s from existing refs.", change.getKey());
-        // Reindex the change asynchronously, ignoring errors.
-        @SuppressWarnings("unused")
-        Future<?> possiblyIgnoredError = indexer.indexAsync(project.getNameKey(), change.getId());
-        return true;
+    try (TraceTimer traceTimer = newTimer("foundInExistingRef")) {
+      for (Ref ref : existingRefs) {
+        ChangeNotes notes =
+            notesFactory.create(project.getNameKey(), Change.Id.fromRef(ref.getName()));
+        Change change = notes.getChange();
+        if (change.getDest().equals(magicBranch.dest)) {
+          logger.atFine().log("Found change %s from existing refs.", change.getKey());
+          // Reindex the change asynchronously, ignoring errors.
+          @SuppressWarnings("unused")
+          Future<?> possiblyIgnoredError = indexer.indexAsync(project.getNameKey(), change.getId());
+          return true;
+        }
       }
+      return false;
     }
-    return false;
   }
 
   private RevCommit setUpWalkForSelectingChanges() throws IOException {
@@ -2465,12 +2470,16 @@
   }
 
   private ChangeLookup lookupByChangeKey(RevCommit c, Change.Key key) {
-    return new ChangeLookup(c, key, queryProvider.get().byBranchKey(magicBranch.dest, key));
+    try (TraceTimer traceTimer = newTimer("lookupByChangeKey")) {
+      return new ChangeLookup(c, key, queryProvider.get().byBranchKey(magicBranch.dest, key));
+    }
   }
 
   private ChangeLookup lookupByCommit(RevCommit c) {
-    return new ChangeLookup(
-        c, null, queryProvider.get().byBranchCommit(magicBranch.dest, c.getName()));
+    try (TraceTimer traceTimer = newTimer("lookupByCommit")) {
+      return new ChangeLookup(
+          c, null, queryProvider.get().byBranchCommit(magicBranch.dest, c.getName()));
+    }
   }
 
   /** Represents a commit for which a Change should be created. */
@@ -2734,7 +2743,7 @@
      * @throws PermissionBackendException
      */
     boolean validateNewPatchSet() throws IOException, PermissionBackendException {
-      try (TraceTimer traceTimer = newTimer(ReplaceRequest.class, "validateNewPatchSet")) {
+      try (TraceTimer traceTimer = newTimer("validateNewPatchSet")) {
         if (!validateNewPatchSetNoteDb()) {
           return false;
         }
@@ -2767,59 +2776,63 @@
 
     /** Validates the new PS against permissions and notedb status. */
     private boolean validateNewPatchSetNoteDb() throws IOException, PermissionBackendException {
-      if (notes == null) {
-        reject(inputCommand, "change " + ontoChange + " not found");
-        return false;
-      }
-
-      Change change = notes.getChange();
-      priorPatchSet = change.currentPatchSetId();
-      if (!revisions.containsValue(priorPatchSet)) {
-        reject(inputCommand, "change " + ontoChange + " missing revisions");
-        return false;
-      }
-
-      RevCommit newCommit = receivePack.getRevWalk().parseCommit(newCommitId);
-
-      // Not allowed to create a new patch set if the current patch set is locked.
-      if (psUtil.isPatchSetLocked(notes)) {
-        reject(inputCommand, "cannot add patch set to " + ontoChange + ".");
-        return false;
-      }
-
-      try {
-        permissions.change(notes).check(ChangePermission.ADD_PATCH_SET);
-      } catch (AuthException no) {
-        reject(inputCommand, "cannot add patch set to " + ontoChange + ".");
-        return false;
-      }
-
-      if (change.isClosed()) {
-        reject(inputCommand, "change " + ontoChange + " closed");
-        return false;
-      } else if (revisions.containsKey(newCommit)) {
-        reject(inputCommand, "commit already exists (in the change)");
-        return false;
-      }
-
-      for (Ref r : receivePack.getRepository().getRefDatabase().getRefsByPrefix("refs/changes")) {
-        if (r.getObjectId().equals(newCommit)) {
-          reject(inputCommand, "commit already exists (in the project)");
+      try (TraceTimer traceTimer = newTimer("validateNewPatchSetNoteDb")) {
+        if (notes == null) {
+          reject(inputCommand, "change " + ontoChange + " not found");
           return false;
         }
-      }
 
-      for (RevCommit prior : revisions.keySet()) {
-        // Don't allow a change to directly depend upon itself. This is a
-        // very common error due to users making a new commit rather than
-        // amending when trying to address review comments.
-        if (receivePack.getRevWalk().isMergedInto(prior, newCommit)) {
-          reject(inputCommand, SAME_CHANGE_ID_IN_MULTIPLE_CHANGES);
+        Change change = notes.getChange();
+        priorPatchSet = change.currentPatchSetId();
+        if (!revisions.containsValue(priorPatchSet)) {
+          reject(inputCommand, "change " + ontoChange + " missing revisions");
           return false;
         }
-      }
 
-      return true;
+        RevCommit newCommit = receivePack.getRevWalk().parseCommit(newCommitId);
+
+        // Not allowed to create a new patch set if the current patch set is locked.
+        if (psUtil.isPatchSetLocked(notes)) {
+          reject(inputCommand, "cannot add patch set to " + ontoChange + ".");
+          return false;
+        }
+
+        try {
+          permissions.change(notes).check(ChangePermission.ADD_PATCH_SET);
+        } catch (AuthException no) {
+          reject(inputCommand, "cannot add patch set to " + ontoChange + ".");
+          return false;
+        }
+
+        if (change.isClosed()) {
+          reject(inputCommand, "change " + ontoChange + " closed");
+          return false;
+        } else if (revisions.containsKey(newCommit)) {
+          reject(inputCommand, "commit already exists (in the change)");
+          return false;
+        }
+
+        for (Ref r : receivePack.getRepository().getRefDatabase().getRefsByPrefix("refs/changes")) {
+          if (r.getObjectId().equals(newCommit)) {
+            reject(inputCommand, "commit already exists (in the project)");
+            return false;
+          }
+        }
+
+        try (TraceTimer traceTimer2 = newTimer("validateNewPatchSetNoteDb#isMergedInto")) {
+          for (RevCommit prior : revisions.keySet()) {
+            // Don't allow a change to directly depend upon itself. This is a
+            // very common error due to users making a new commit rather than
+            // amending when trying to address review comments.
+            if (receivePack.getRevWalk().isMergedInto(prior, newCommit)) {
+              reject(inputCommand, SAME_CHANGE_ID_IN_MULTIPLE_CHANGES);
+              return false;
+            }
+          }
+        }
+
+        return true;
+      }
     }
 
     /** Validates whether the WIP change is allowed. Rejects inputCommand if not. */
@@ -2848,39 +2861,41 @@
 
     /** prints a warning if the new PS has the same tree as the previous commit. */
     private void sameTreeWarning() throws IOException {
-      RevWalk rw = receivePack.getRevWalk();
-      RevCommit newCommit = rw.parseCommit(newCommitId);
-      RevCommit priorCommit = revisions.inverse().get(priorPatchSet);
+      try (TraceTimer traceTimer = newTimer("sameTreeWarning")) {
+        RevWalk rw = receivePack.getRevWalk();
+        RevCommit newCommit = rw.parseCommit(newCommitId);
+        RevCommit priorCommit = revisions.inverse().get(priorPatchSet);
 
-      if (newCommit.getTree().equals(priorCommit.getTree())) {
-        rw.parseBody(newCommit);
-        rw.parseBody(priorCommit);
-        boolean messageEq =
-            Objects.equals(newCommit.getFullMessage(), priorCommit.getFullMessage());
-        boolean parentsEq = parentsEqual(newCommit, priorCommit);
-        boolean authorEq = authorEqual(newCommit, priorCommit);
-        ObjectReader reader = receivePack.getRevWalk().getObjectReader();
+        if (newCommit.getTree().equals(priorCommit.getTree())) {
+          rw.parseBody(newCommit);
+          rw.parseBody(priorCommit);
+          boolean messageEq =
+              Objects.equals(newCommit.getFullMessage(), priorCommit.getFullMessage());
+          boolean parentsEq = parentsEqual(newCommit, priorCommit);
+          boolean authorEq = authorEqual(newCommit, priorCommit);
+          ObjectReader reader = receivePack.getRevWalk().getObjectReader();
 
-        if (messageEq && parentsEq && authorEq) {
-          addMessage(
-              String.format(
-                  "warning: no changes between prior commit %s and new commit %s",
-                  abbreviateName(priorCommit, reader), abbreviateName(newCommit, reader)));
-        } else {
-          StringBuilder msg = new StringBuilder();
-          msg.append("warning: ").append(abbreviateName(newCommit, reader));
-          msg.append(":");
-          msg.append(" no files changed");
-          if (!authorEq) {
-            msg.append(", author changed");
+          if (messageEq && parentsEq && authorEq) {
+            addMessage(
+                String.format(
+                    "warning: no changes between prior commit %s and new commit %s",
+                    abbreviateName(priorCommit, reader), abbreviateName(newCommit, reader)));
+          } else {
+            StringBuilder msg = new StringBuilder();
+            msg.append("warning: ").append(abbreviateName(newCommit, reader));
+            msg.append(":");
+            msg.append(" no files changed");
+            if (!authorEq) {
+              msg.append(", author changed");
+            }
+            if (!messageEq) {
+              msg.append(", message updated");
+            }
+            if (!parentsEq) {
+              msg.append(", was rebased");
+            }
+            addMessage(msg.toString());
           }
-          if (!messageEq) {
-            msg.append(", message updated");
-          }
-          if (!parentsEq) {
-            msg.append(", was rebased");
-          }
-          addMessage(msg.toString());
         }
       }
     }
@@ -2890,33 +2905,36 @@
      * failure.
      */
     private boolean newEdit() {
-      psId = notes.getChange().currentPatchSetId();
-      Optional<ChangeEdit> edit;
+      try (TraceTimer traceTimer = newTimer("newEdit")) {
+        psId = notes.getChange().currentPatchSetId();
+        Optional<ChangeEdit> edit;
 
-      try {
-        edit = editUtil.byChange(notes, user);
-      } catch (AuthException | IOException e) {
-        logger.atSevere().withCause(e).log("Cannot retrieve edit");
-        return false;
-      }
+        try {
+          edit = editUtil.byChange(notes, user);
+        } catch (AuthException | IOException e) {
+          logger.atSevere().withCause(e).log("Cannot retrieve edit");
+          return false;
+        }
 
-      if (edit.isPresent()) {
-        if (edit.get().getBasePatchSet().id().equals(psId)) {
-          // replace edit
-          cmd =
-              new ReceiveCommand(edit.get().getEditCommit(), newCommitId, edit.get().getRefName());
+        if (edit.isPresent()) {
+          if (edit.get().getBasePatchSet().id().equals(psId)) {
+            // replace edit
+            cmd =
+                new ReceiveCommand(
+                    edit.get().getEditCommit(), newCommitId, edit.get().getRefName());
+          } else {
+            // delete old edit ref on rebase
+            prev =
+                new ReceiveCommand(
+                    edit.get().getEditCommit(), ObjectId.zeroId(), edit.get().getRefName());
+            createEditCommand();
+          }
         } else {
-          // delete old edit ref on rebase
-          prev =
-              new ReceiveCommand(
-                  edit.get().getEditCommit(), ObjectId.zeroId(), edit.get().getRefName());
           createEditCommand();
         }
-      } else {
-        createEditCommand();
-      }
 
-      return true;
+        return true;
+      }
     }
 
     /** Creates a ReceiveCommand for a new edit. */
@@ -2930,15 +2948,18 @@
 
     /** Updates 'this' to add a new patchset. */
     private void newPatchSet() throws IOException {
-      RevCommit newCommit = receivePack.getRevWalk().parseCommit(newCommitId);
-      psId =
-          ChangeUtil.nextPatchSetIdFromAllRefsMap(allRefs(), notes.getChange().currentPatchSetId());
-      info = patchSetInfoFactory.get(receivePack.getRevWalk(), newCommit, psId);
-      cmd = new ReceiveCommand(ObjectId.zeroId(), newCommitId, psId.toRefName());
+      try (TraceTimer traceTimer = newTimer("newPatchSet")) {
+        RevCommit newCommit = receivePack.getRevWalk().parseCommit(newCommitId);
+        psId =
+            ChangeUtil.nextPatchSetIdFromAllRefsMap(
+                allRefs(), notes.getChange().currentPatchSetId());
+        info = patchSetInfoFactory.get(receivePack.getRevWalk(), newCommit, psId);
+        cmd = new ReceiveCommand(ObjectId.zeroId(), newCommitId, psId.toRefName());
+      }
     }
 
     void addOps(BatchUpdate bu, @Nullable Task progress) throws IOException {
-      try (TraceTimer traceTimer = newTimer(ReplaceRequest.class, "addOps")) {
+      try (TraceTimer traceTimer = newTimer("addOps")) {
         if (magicBranch != null && magicBranch.edit) {
           bu.addOp(notes.getChangeId(), new ReindexOnlyOp());
           if (prev != null) {
@@ -3075,7 +3096,11 @@
   }
 
   private void initChangeRefMaps() {
-    if (refsByChange == null) {
+    if (refsByChange != null) {
+      return;
+    }
+
+    try (TraceTimer traceTimer = newTimer("initChangeRefMaps")) {
       int estRefsPerChange = 4;
       refsById = MultimapBuilder.hashKeys().arrayListValues().build();
       refsByChange =
@@ -3317,7 +3342,7 @@
                 }
 
                 logger.atFine().log(
-                    "Auto-closing %s changes with existing patch sets and %s with new patch sets",
+                    "Auto-closing %d changes with existing patch sets and %d with new patch sets",
                     existingPatchSets, newPatchSets);
                 bu.execute();
               } catch (IOException | StorageException | PermissionBackendException e) {
diff --git a/java/com/google/gerrit/server/logging/CallerFinder.java b/java/com/google/gerrit/server/logging/CallerFinder.java
index 73ffeb5..bd7e608 100644
--- a/java/com/google/gerrit/server/logging/CallerFinder.java
+++ b/java/com/google/gerrit/server/logging/CallerFinder.java
@@ -142,7 +142,7 @@
 
   /**
    * The minimum number of calls known to have occurred between the first call to the target class
-   * and the call of {@link #findCaller()}. If in doubt, specify zero here to avoid accidentally
+   * and the call of {@link #findCallerLazy()}. If in doubt, specify zero here to avoid accidentally
    * skipping past the caller.
    *
    * @return the number of stack elements to skip when computing the caller
@@ -195,7 +195,7 @@
     public abstract CallerFinder build();
   }
 
-  public LazyArg<String> findCaller() {
+  public LazyArg<String> findCallerLazy() {
     return lazy(
         () ->
             targets().stream()
diff --git a/java/com/google/gerrit/server/logging/Metadata.java b/java/com/google/gerrit/server/logging/Metadata.java
index dae78c0..7af204e 100644
--- a/java/com/google/gerrit/server/logging/Metadata.java
+++ b/java/com/google/gerrit/server/logging/Metadata.java
@@ -18,11 +18,14 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.base.MoreObjects.ToStringHelper;
 import com.google.common.collect.ImmutableList;
+import com.google.common.flogger.LazyArg;
+import com.google.common.flogger.LazyArgs;
 import com.google.gerrit.common.Nullable;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
 import java.util.Arrays;
+import java.util.Comparator;
 import java.util.Optional;
 
 /** Metadata that is provided to {@link PerformanceLogger}s as context for performance records. */
@@ -141,7 +144,8 @@
   public abstract Optional<String> username();
 
   /**
-   * Returns a string representation of this instance that is suitable for logging.
+   * Returns a string representation of this instance that is suitable for logging. This is wrapped
+   * in a {@link LazyArg} because it is expensive to evaluate.
    *
    * <p>{@link #toString()} formats the {@link Optional} fields as {@code key=Optional[value]} or
    * {@code key=Optional.empty}. Since this class has many optional fields from which usually only a
@@ -178,7 +182,14 @@
    *
    * @return string representation of this instance that is suitable for logging
    */
-  public String toStringForLogging() {
+  LazyArg<String> toStringForLoggingLazy() {
+    // Don't use a lambda because different compilers generate different method names for lambdas,
+    // e.g. "lambda$myFunction$0" vs. just "lambda$0" in Eclipse. We need to identify the method
+    // by name to skip it and avoid infinite recursion.
+    return LazyArgs.lazy(this::toStringForLoggingImpl);
+  }
+
+  private String toStringForLoggingImpl() {
     // Append class name.
     String className = getClass().getSimpleName();
     if (className.startsWith("AutoValue_")) {
@@ -188,15 +199,16 @@
 
     // Append key-value pairs for field which are set.
     Method[] methods = Metadata.class.getDeclaredMethods();
-    Arrays.<Method>sort(methods, (m1, m2) -> m1.getName().compareTo(m2.getName()));
+    Arrays.sort(methods, Comparator.comparing(Method::getName));
     for (Method method : methods) {
       if (Modifier.isStatic(method.getModifiers())) {
         // skip static method
         continue;
       }
 
-      if (method.getName().equals(Thread.currentThread().getStackTrace()[1].getMethodName())) {
-        // skip this method (toStringForLogging() method)
+      if (method.getName().equals("toStringForLoggingLazy")
+          || method.getName().equals("toStringForLoggingImpl")) {
+        // Don't call myself in infinite recursion.
         continue;
       }
 
diff --git a/java/com/google/gerrit/server/logging/TraceContext.java b/java/com/google/gerrit/server/logging/TraceContext.java
index 30c5250..21a4ce6 100644
--- a/java/com/google/gerrit/server/logging/TraceContext.java
+++ b/java/com/google/gerrit/server/logging/TraceContext.java
@@ -196,13 +196,13 @@
       this(
           () ->
               logger.atFine().log(
-                  "Starting timer for %s (%s)", operation, metadata.toStringForLogging()),
+                  "Starting timer for %s (%s)", operation, metadata.toStringForLoggingLazy()),
           elapsedMs -> {
             LoggingContext.getInstance()
                 .addPerformanceLogRecord(
                     () -> PerformanceLogRecord.create(operation, elapsedMs, metadata));
             logger.atFine().log(
-                "%s (%s) done (%d ms)", operation, metadata.toStringForLogging(), elapsedMs);
+                "%s (%s) done (%d ms)", operation, metadata.toStringForLoggingLazy(), elapsedMs);
           });
     }
 
diff --git a/java/com/google/gerrit/server/permissions/RefControl.java b/java/com/google/gerrit/server/permissions/RefControl.java
index 9a2ecdd..694bb82 100644
--- a/java/com/google/gerrit/server/permissions/RefControl.java
+++ b/java/com/google/gerrit/server/permissions/RefControl.java
@@ -395,7 +395,7 @@
           withForce,
           projectControl.getProject().getName(),
           refName,
-          callerFinder.findCaller());
+          callerFinder.findCallerLazy());
       return false;
     }
 
@@ -408,7 +408,7 @@
             withForce,
             projectControl.getProject().getName(),
             refName,
-            callerFinder.findCaller());
+            callerFinder.findCallerLazy());
         return true;
       }
     }
@@ -420,7 +420,7 @@
         withForce,
         projectControl.getProject().getName(),
         refName,
-        callerFinder.findCaller());
+        callerFinder.findCallerLazy());
     return false;
   }
 
diff --git a/java/com/google/gerrit/sshd/commands/Upload.java b/java/com/google/gerrit/sshd/commands/Upload.java
index 41323dd..87ae493 100644
--- a/java/com/google/gerrit/sshd/commands/Upload.java
+++ b/java/com/google/gerrit/sshd/commands/Upload.java
@@ -21,6 +21,7 @@
 import com.google.gerrit.server.RequestInfo;
 import com.google.gerrit.server.RequestListener;
 import com.google.gerrit.server.git.PermissionAwareRepositoryManager;
+import com.google.gerrit.server.git.TracingHook;
 import com.google.gerrit.server.git.TransferConfig;
 import com.google.gerrit.server.git.UploadPackInitializer;
 import com.google.gerrit.server.git.validators.UploadValidationException;
@@ -83,13 +84,14 @@
     for (UploadPackInitializer initializer : uploadPackInitializers) {
       initializer.init(projectState.getNameKey(), up);
     }
-    try (TraceContext traceContext = TraceContext.open()) {
+    try (TraceContext traceContext = TraceContext.open();
+        TracingHook tracingHook = new TracingHook()) {
       RequestInfo requestInfo =
           RequestInfo.builder(RequestInfo.RequestType.GIT_UPLOAD, user, traceContext)
               .project(projectState.getNameKey())
               .build();
       requestListeners.runEach(l -> l.onRequest(requestInfo));
-
+      up.setProtocolV2Hook(tracingHook);
       up.upload(in, out, err);
       session.setPeerAgent(up.getPeerUserAgent());
     } catch (UploadValidationException e) {
diff --git a/javatests/com/google/gerrit/acceptance/TestGroupBackendTest.java b/javatests/com/google/gerrit/acceptance/TestGroupBackendTest.java
index fc42474..d8ed29a 100644
--- a/javatests/com/google/gerrit/acceptance/TestGroupBackendTest.java
+++ b/javatests/com/google/gerrit/acceptance/TestGroupBackendTest.java
@@ -16,18 +16,16 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.reviewdb.client.AccountGroup;
-import com.google.gerrit.server.account.GroupBackend;
 import com.google.gerrit.server.account.UniversalGroupBackend;
 import com.google.gerrit.server.group.testing.TestGroupBackend;
 import com.google.inject.Inject;
 import org.junit.Test;
 
 public class TestGroupBackendTest extends AbstractDaemonTest {
-  @Inject private DynamicSet<GroupBackend> groupBackends;
   @Inject private UniversalGroupBackend universalGroupBackend;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   private final TestGroupBackend testGroupBackend = new TestGroupBackend();
   private final AccountGroup.UUID testUUID = AccountGroup.uuid("testbackend:test");
@@ -39,11 +37,8 @@
 
   @Test
   public void universalGroupBackendHandlesTestGroup() throws Exception {
-    RegistrationHandle registrationHandle = groupBackends.add("gerrit", testGroupBackend);
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(testGroupBackend)) {
       assertThat(universalGroupBackend.handles(testUUID)).isTrue();
-    } finally {
-      registrationHandle.remove();
     }
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
index 47bc7b3..6c61ae9 100644
--- a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
@@ -57,6 +57,8 @@
 import com.google.common.util.concurrent.AtomicLongMap;
 import com.google.common.util.concurrent.Runnables;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.Sandboxed;
@@ -98,7 +100,6 @@
 import com.google.gerrit.extensions.events.AccountIndexedListener;
 import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
 import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
@@ -189,7 +190,6 @@
 import org.eclipse.jgit.transport.RemoteRefUpdate;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 public class AccountIT extends AbstractDaemonTest {
@@ -207,8 +207,6 @@
 
   @Inject private @ServerInitiated Provider<AccountsUpdate> accountsUpdateProvider;
   @Inject private AccountIndexer accountIndexer;
-  @Inject private DynamicSet<AccountIndexedListener> accountIndexedListeners;
-  @Inject private DynamicSet<GitReferenceUpdatedListener> refUpdateListeners;
   @Inject private ExternalIdNotes.Factory extIdNotesFactory;
   @Inject private ExternalIds externalIds;
   @Inject private GitReferenceUpdated gitReferenceUpdated;
@@ -222,6 +220,7 @@
   @Inject private StalenessChecker stalenessChecker;
   @Inject private VersionedAuthorizedKeys.Accessor authorizedKeys;
   @Inject private PermissionBackend permissionBackend;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Inject protected Emails emails;
 
@@ -231,42 +230,8 @@
 
   @Inject private AccountOperations accountOperations;
 
-  @Inject
-  private DynamicSet<AccountActivationValidationListener> accountActivationValidationListeners;
-
   @Inject protected GroupOperations groupOperations;
 
-  private AccountIndexedCounter accountIndexedCounter;
-  private RegistrationHandle accountIndexEventCounterHandle;
-  private RefUpdateCounter refUpdateCounter;
-  private RegistrationHandle refUpdateCounterHandle;
-
-  @Before
-  public void addAccountIndexEventCounter() {
-    accountIndexedCounter = new AccountIndexedCounter();
-    accountIndexEventCounterHandle = accountIndexedListeners.add("gerrit", accountIndexedCounter);
-  }
-
-  @After
-  public void removeAccountIndexEventCounter() {
-    if (accountIndexEventCounterHandle != null) {
-      accountIndexEventCounterHandle.remove();
-    }
-  }
-
-  @Before
-  public void addRefUpdateCounter() {
-    refUpdateCounter = new RefUpdateCounter();
-    refUpdateCounterHandle = refUpdateListeners.add("gerrit", refUpdateCounter);
-  }
-
-  @After
-  public void removeRefUpdateCounter() {
-    if (refUpdateCounterHandle != null) {
-      refUpdateCounterHandle.remove();
-    }
-  }
-
   @After
   public void clearPublicKeyStore() throws Exception {
     try (Repository repo = repoManager.openRepository(allUsers)) {
@@ -315,11 +280,14 @@
 
   @Test
   public void createByAccountCreator() throws Exception {
-    Account.Id accountId = createByAccountCreator(1);
-    refUpdateCounter.assertRefUpdateFor(
-        RefUpdateCounter.projectRef(allUsers, RefNames.refsUsers(accountId)),
-        RefUpdateCounter.projectRef(allUsers, RefNames.REFS_EXTERNAL_IDS),
-        RefUpdateCounter.projectRef(allUsers, RefNames.REFS_SEQUENCES + Sequences.NAME_ACCOUNTS));
+    RefUpdateCounter refUpdateCounter = new RefUpdateCounter();
+    try (Registration registration = extensionRegistry.newRegistration().add(refUpdateCounter)) {
+      Account.Id accountId = createByAccountCreator(1);
+      refUpdateCounter.assertRefUpdateFor(
+          RefUpdateCounter.projectRef(allUsers, RefNames.refsUsers(accountId)),
+          RefUpdateCounter.projectRef(allUsers, RefNames.REFS_EXTERNAL_IDS),
+          RefUpdateCounter.projectRef(allUsers, RefNames.REFS_SEQUENCES + Sequences.NAME_ACCOUNTS));
+    }
   }
 
   @Test
@@ -338,42 +306,54 @@
   }
 
   private Account.Id createByAccountCreator(int expectedAccountReindexCalls) throws Exception {
-    String name = "foo";
-    TestAccount foo = accountCreator.create(name);
-    AccountInfo info = gApi.accounts().id(foo.id().get()).get();
-    assertThat(info.username).isEqualTo(name);
-    assertThat(info.name).isEqualTo(name);
-    accountIndexedCounter.assertReindexOf(foo, expectedAccountReindexCalls);
-    assertUserBranch(foo.id(), name, null);
-    return foo.id();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String name = "foo";
+      TestAccount foo = accountCreator.create(name);
+      AccountInfo info = gApi.accounts().id(foo.id().get()).get();
+      assertThat(info.username).isEqualTo(name);
+      assertThat(info.name).isEqualTo(name);
+      accountIndexedCounter.assertReindexOf(foo, expectedAccountReindexCalls);
+      assertUserBranch(foo.id(), name, null);
+      return foo.id();
+    }
   }
 
   @Test
   public void createAnonymousCowardByAccountCreator() throws Exception {
-    TestAccount anonymousCoward = accountCreator.create();
-    accountIndexedCounter.assertReindexOf(anonymousCoward);
-    assertUserBranchWithoutAccountConfig(anonymousCoward.id());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount anonymousCoward = accountCreator.create();
+      accountIndexedCounter.assertReindexOf(anonymousCoward);
+      assertUserBranchWithoutAccountConfig(anonymousCoward.id());
+    }
   }
 
   @Test
   public void create() throws Exception {
-    AccountInput input = new AccountInput();
-    input.username = "foo";
-    input.name = "Foo";
-    input.email = "foo@example.com";
-    AccountInfo accountInfo = gApi.accounts().create(input).get();
-    assertThat(accountInfo._accountId).isNotNull();
-    assertThat(accountInfo.username).isEqualTo(input.username);
-    assertThat(accountInfo.name).isEqualTo(input.name);
-    assertThat(accountInfo.email).isEqualTo(input.email);
-    assertThat(accountInfo.status).isNull();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      AccountInput input = new AccountInput();
+      input.username = "foo";
+      input.name = "Foo";
+      input.email = "foo@example.com";
+      AccountInfo accountInfo = gApi.accounts().create(input).get();
+      assertThat(accountInfo._accountId).isNotNull();
+      assertThat(accountInfo.username).isEqualTo(input.username);
+      assertThat(accountInfo.name).isEqualTo(input.name);
+      assertThat(accountInfo.email).isEqualTo(input.email);
+      assertThat(accountInfo.status).isNull();
 
-    Account.Id accountId = Account.id(accountInfo._accountId);
-    accountIndexedCounter.assertReindexOf(accountId, 1);
-    assertThat(externalIds.byAccount(accountId))
-        .containsExactly(
-            ExternalId.createUsername(input.username, accountId, null),
-            ExternalId.createEmail(accountId, input.email));
+      Account.Id accountId = Account.id(accountInfo._accountId);
+      accountIndexedCounter.assertReindexOf(accountId, 1);
+      assertThat(externalIds.byAccount(accountId))
+          .containsExactly(
+              ExternalId.createUsername(input.username, accountId, null),
+              ExternalId.createEmail(accountId, input.email));
+    }
   }
 
   @Test
@@ -517,69 +497,93 @@
 
   @Test
   public void get() throws Exception {
-    AccountInfo info = gApi.accounts().id("admin").get();
-    assertThat(info.name).isEqualTo("Administrator");
-    assertThat(info.email).isEqualTo("admin@example.com");
-    assertThat(info.username).isEqualTo("admin");
-    accountIndexedCounter.assertNoReindex();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      AccountInfo info = gApi.accounts().id("admin").get();
+      assertThat(info.name).isEqualTo("Administrator");
+      assertThat(info.email).isEqualTo("admin@example.com");
+      assertThat(info.username).isEqualTo("admin");
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void getByIntId() throws Exception {
-    AccountInfo info = gApi.accounts().id("admin").get();
-    AccountInfo infoByIntId = gApi.accounts().id(info._accountId).get();
-    assertThat(info.name).isEqualTo(infoByIntId.name);
-    accountIndexedCounter.assertNoReindex();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      AccountInfo info = gApi.accounts().id("admin").get();
+      AccountInfo infoByIntId = gApi.accounts().id(info._accountId).get();
+      assertThat(info.name).isEqualTo(infoByIntId.name);
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void self() throws Exception {
-    AccountInfo info = gApi.accounts().self().get();
-    assertUser(info, admin);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      AccountInfo info = gApi.accounts().self().get();
+      assertUser(info, admin);
 
-    info = gApi.accounts().id("self").get();
-    assertUser(info, admin);
-    accountIndexedCounter.assertNoReindex();
+      info = gApi.accounts().id("self").get();
+      assertUser(info, admin);
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void active() throws Exception {
-    int id = gApi.accounts().id("user").get()._accountId;
-    assertThat(gApi.accounts().id("user").getActive()).isTrue();
-    gApi.accounts().id("user").setActive(false);
-    accountIndexedCounter.assertReindexOf(user);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      int id = gApi.accounts().id("user").get()._accountId;
+      assertThat(gApi.accounts().id("user").getActive()).isTrue();
+      gApi.accounts().id("user").setActive(false);
+      accountIndexedCounter.assertReindexOf(user);
 
-    // Inactive users may only be resolved by ID.
-    ResourceNotFoundException thrown =
-        assertThrows(ResourceNotFoundException.class, () -> gApi.accounts().id("user"));
-    assertThat(thrown)
-        .hasMessageThat()
-        .isEqualTo(
-            "Account 'user' only matches inactive accounts. To use an inactive account, retry"
-                + " with one of the following exact account IDs:\n"
-                + id
-                + ": User <user@example.com>");
-    assertThat(gApi.accounts().id(id).getActive()).isFalse();
+      // Inactive users may only be resolved by ID.
+      ResourceNotFoundException thrown =
+          assertThrows(ResourceNotFoundException.class, () -> gApi.accounts().id("user"));
+      assertThat(thrown)
+          .hasMessageThat()
+          .isEqualTo(
+              "Account 'user' only matches inactive accounts. To use an inactive account, retry"
+                  + " with one of the following exact account IDs:\n"
+                  + id
+                  + ": User <user@example.com>");
+      assertThat(gApi.accounts().id(id).getActive()).isFalse();
 
-    gApi.accounts().id(id).setActive(true);
-    assertThat(gApi.accounts().id("user").getActive()).isTrue();
-    accountIndexedCounter.assertReindexOf(user);
+      gApi.accounts().id(id).setActive(true);
+      assertThat(gApi.accounts().id("user").getActive()).isTrue();
+      accountIndexedCounter.assertReindexOf(user);
+    }
   }
 
   @Test
   public void shouldAllowQueryByEmailForInactiveUser() throws Exception {
-    Account.Id activatableAccountId =
-        accountOperations.newAccount().inactive().preferredEmail("foo@activatable.com").create();
-    accountIndexedCounter.assertReindexOf(activatableAccountId, 1);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      Account.Id activatableAccountId =
+          accountOperations.newAccount().inactive().preferredEmail("foo@activatable.com").create();
+      accountIndexedCounter.assertReindexOf(activatableAccountId, 1);
+    }
 
     gApi.changes().query("owner:foo@activatable.com").get();
   }
 
   @Test
   public void shouldAllowQueryByUserNameForInactiveUser() throws Exception {
-    Account.Id activatableAccountId =
-        accountOperations.newAccount().inactive().username("foo").create();
-    accountIndexedCounter.assertReindexOf(activatableAccountId, 1);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      Account.Id activatableAccountId =
+          accountOperations.newAccount().inactive().username("foo").create();
+      accountIndexedCounter.assertReindexOf(activatableAccountId, 1);
+    }
 
     gApi.changes().query("owner:foo").get();
   }
@@ -590,27 +594,26 @@
         accountOperations.newAccount().inactive().preferredEmail("foo@activatable.com").create();
     Account.Id deactivatableAccountId =
         accountOperations.newAccount().preferredEmail("foo@deactivatable.com").create();
-    RegistrationHandle registrationHandle =
-        accountActivationValidationListeners.add(
-            "gerrit",
-            new AccountActivationValidationListener() {
-              @Override
-              public void validateActivation(AccountState account) throws ValidationException {
-                String preferredEmail = account.account().preferredEmail();
-                if (preferredEmail == null || !preferredEmail.endsWith("@activatable.com")) {
-                  throw new ValidationException("not allowed to active account");
-                }
-              }
 
-              @Override
-              public void validateDeactivation(AccountState account) throws ValidationException {
-                String preferredEmail = account.account().preferredEmail();
-                if (preferredEmail == null || !preferredEmail.endsWith("@deactivatable.com")) {
-                  throw new ValidationException("not allowed to deactive account");
-                }
-              }
-            });
-    try {
+    AccountActivationValidationListener listener =
+        new AccountActivationValidationListener() {
+          @Override
+          public void validateActivation(AccountState account) throws ValidationException {
+            String preferredEmail = account.account().preferredEmail();
+            if (preferredEmail == null || !preferredEmail.endsWith("@activatable.com")) {
+              throw new ValidationException("not allowed to active account");
+            }
+          }
+
+          @Override
+          public void validateDeactivation(AccountState account) throws ValidationException {
+            String preferredEmail = account.account().preferredEmail();
+            if (preferredEmail == null || !preferredEmail.endsWith("@deactivatable.com")) {
+              throw new ValidationException("not allowed to deactive account");
+            }
+          }
+        };
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
       /* Test account that can be activated, but not deactivated */
       // Deactivate account that is already inactive
       ResourceConflictException thrown =
@@ -660,8 +663,6 @@
               () -> gApi.accounts().id(deactivatableAccountId.get()).setActive(true));
       assertThat(thrown).hasMessageThat().isEqualTo("not allowed to active account");
       assertThat(accountOperations.account(deactivatableAccountId).get().active()).isFalse();
-    } finally {
-      registrationHandle.remove();
     }
   }
 
@@ -688,84 +689,96 @@
 
   @Test
   public void starUnstarChange() throws Exception {
-    PushOneCommit.Result r = createChange();
-    String triplet = project.get() + "~master~" + r.getChangeId();
-    refUpdateCounter.clear();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    RefUpdateCounter refUpdateCounter = new RefUpdateCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter).add(refUpdateCounter)) {
+      PushOneCommit.Result r = createChange();
+      String triplet = project.get() + "~master~" + r.getChangeId();
+      refUpdateCounter.clear();
 
-    gApi.accounts().self().starChange(triplet);
-    ChangeInfo change = info(triplet);
-    assertThat(change.starred).isTrue();
-    assertThat(change.stars).contains(DEFAULT_LABEL);
-    refUpdateCounter.assertRefUpdateFor(
-        RefUpdateCounter.projectRef(
-            allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
+      gApi.accounts().self().starChange(triplet);
+      ChangeInfo change = info(triplet);
+      assertThat(change.starred).isTrue();
+      assertThat(change.stars).contains(DEFAULT_LABEL);
+      refUpdateCounter.assertRefUpdateFor(
+          RefUpdateCounter.projectRef(
+              allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
 
-    gApi.accounts().self().unstarChange(triplet);
-    change = info(triplet);
-    assertThat(change.starred).isNull();
-    assertThat(change.stars).isNull();
-    refUpdateCounter.assertRefUpdateFor(
-        RefUpdateCounter.projectRef(
-            allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
+      gApi.accounts().self().unstarChange(triplet);
+      change = info(triplet);
+      assertThat(change.starred).isNull();
+      assertThat(change.stars).isNull();
+      refUpdateCounter.assertRefUpdateFor(
+          RefUpdateCounter.projectRef(
+              allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
 
-    accountIndexedCounter.assertNoReindex();
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void starUnstarChangeWithLabels() throws Exception {
-    PushOneCommit.Result r = createChange();
-    String triplet = project.get() + "~master~" + r.getChangeId();
-    refUpdateCounter.clear();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    RefUpdateCounter refUpdateCounter = new RefUpdateCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter).add(refUpdateCounter)) {
+      PushOneCommit.Result r = createChange();
+      String triplet = project.get() + "~master~" + r.getChangeId();
+      refUpdateCounter.clear();
 
-    assertThat(gApi.accounts().self().getStars(triplet)).isEmpty();
-    assertThat(gApi.accounts().self().getStarredChanges()).isEmpty();
+      assertThat(gApi.accounts().self().getStars(triplet)).isEmpty();
+      assertThat(gApi.accounts().self().getStarredChanges()).isEmpty();
 
-    gApi.accounts()
-        .self()
-        .setStars(triplet, new StarsInput(ImmutableSet.of(DEFAULT_LABEL, "red", "blue")));
-    ChangeInfo change = info(triplet);
-    assertThat(change.starred).isTrue();
-    assertThat(change.stars).containsExactly("blue", "red", DEFAULT_LABEL).inOrder();
-    assertThat(gApi.accounts().self().getStars(triplet))
-        .containsExactly("blue", "red", DEFAULT_LABEL)
-        .inOrder();
-    List<ChangeInfo> starredChanges = gApi.accounts().self().getStarredChanges();
-    assertThat(starredChanges).hasSize(1);
-    ChangeInfo starredChange = starredChanges.get(0);
-    assertThat(starredChange._number).isEqualTo(r.getChange().getId().get());
-    assertThat(starredChange.starred).isTrue();
-    assertThat(starredChange.stars).containsExactly("blue", "red", DEFAULT_LABEL).inOrder();
-    refUpdateCounter.assertRefUpdateFor(
-        RefUpdateCounter.projectRef(
-            allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
+      gApi.accounts()
+          .self()
+          .setStars(triplet, new StarsInput(ImmutableSet.of(DEFAULT_LABEL, "red", "blue")));
+      ChangeInfo change = info(triplet);
+      assertThat(change.starred).isTrue();
+      assertThat(change.stars).containsExactly("blue", "red", DEFAULT_LABEL).inOrder();
+      assertThat(gApi.accounts().self().getStars(triplet))
+          .containsExactly("blue", "red", DEFAULT_LABEL)
+          .inOrder();
+      List<ChangeInfo> starredChanges = gApi.accounts().self().getStarredChanges();
+      assertThat(starredChanges).hasSize(1);
+      ChangeInfo starredChange = starredChanges.get(0);
+      assertThat(starredChange._number).isEqualTo(r.getChange().getId().get());
+      assertThat(starredChange.starred).isTrue();
+      assertThat(starredChange.stars).containsExactly("blue", "red", DEFAULT_LABEL).inOrder();
+      refUpdateCounter.assertRefUpdateFor(
+          RefUpdateCounter.projectRef(
+              allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
 
-    gApi.accounts()
-        .self()
-        .setStars(
-            triplet,
-            new StarsInput(ImmutableSet.of("yellow"), ImmutableSet.of(DEFAULT_LABEL, "blue")));
-    change = info(triplet);
-    assertThat(change.starred).isNull();
-    assertThat(change.stars).containsExactly("red", "yellow").inOrder();
-    assertThat(gApi.accounts().self().getStars(triplet)).containsExactly("red", "yellow").inOrder();
-    starredChanges = gApi.accounts().self().getStarredChanges();
-    assertThat(starredChanges).hasSize(1);
-    starredChange = starredChanges.get(0);
-    assertThat(starredChange._number).isEqualTo(r.getChange().getId().get());
-    assertThat(starredChange.starred).isNull();
-    assertThat(starredChange.stars).containsExactly("red", "yellow").inOrder();
-    refUpdateCounter.assertRefUpdateFor(
-        RefUpdateCounter.projectRef(
-            allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
+      gApi.accounts()
+          .self()
+          .setStars(
+              triplet,
+              new StarsInput(ImmutableSet.of("yellow"), ImmutableSet.of(DEFAULT_LABEL, "blue")));
+      change = info(triplet);
+      assertThat(change.starred).isNull();
+      assertThat(change.stars).containsExactly("red", "yellow").inOrder();
+      assertThat(gApi.accounts().self().getStars(triplet))
+          .containsExactly("red", "yellow")
+          .inOrder();
+      starredChanges = gApi.accounts().self().getStarredChanges();
+      assertThat(starredChanges).hasSize(1);
+      starredChange = starredChanges.get(0);
+      assertThat(starredChange._number).isEqualTo(r.getChange().getId().get());
+      assertThat(starredChange.starred).isNull();
+      assertThat(starredChange.stars).containsExactly("red", "yellow").inOrder();
+      refUpdateCounter.assertRefUpdateFor(
+          RefUpdateCounter.projectRef(
+              allUsers, RefNames.refsStarredChanges(Change.id(change._number), admin.id())));
 
-    accountIndexedCounter.assertNoReindex();
+      accountIndexedCounter.assertNoReindex();
 
-    requestScopeOperations.setApiUser(user.id());
-    AuthException thrown =
-        assertThrows(
-            AuthException.class,
-            () -> gApi.accounts().id(Integer.toString((admin.id().get()))).getStars(triplet));
-    assertThat(thrown).hasMessageThat().contains("not allowed to get stars of another account");
+      requestScopeOperations.setApiUser(user.id());
+      AuthException thrown =
+          assertThrows(
+              AuthException.class,
+              () -> gApi.accounts().id(Integer.toString((admin.id().get()))).getStars(triplet));
+      assertThat(thrown).hasMessageThat().contains("not allowed to get stars of another account");
+    }
   }
 
   @Test
@@ -825,65 +838,81 @@
 
   @Test
   public void ignoreChangeBySetStars() throws Exception {
-    TestAccount user2 = accountCreator.user2();
-    accountIndexedCounter.clear();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount user2 = accountCreator.user2();
+      accountIndexedCounter.clear();
 
-    PushOneCommit.Result r = createChange();
+      PushOneCommit.Result r = createChange();
 
-    AddReviewerInput in = new AddReviewerInput();
-    in.reviewer = user.email();
-    gApi.changes().id(r.getChangeId()).addReviewer(in);
+      AddReviewerInput in = new AddReviewerInput();
+      in.reviewer = user.email();
+      gApi.changes().id(r.getChangeId()).addReviewer(in);
 
-    in = new AddReviewerInput();
-    in.reviewer = user2.email();
-    gApi.changes().id(r.getChangeId()).addReviewer(in);
+      in = new AddReviewerInput();
+      in.reviewer = user2.email();
+      gApi.changes().id(r.getChangeId()).addReviewer(in);
 
-    requestScopeOperations.setApiUser(user.id());
-    gApi.accounts().self().setStars(r.getChangeId(), new StarsInput(ImmutableSet.of(IGNORE_LABEL)));
+      requestScopeOperations.setApiUser(user.id());
+      gApi.accounts()
+          .self()
+          .setStars(r.getChangeId(), new StarsInput(ImmutableSet.of(IGNORE_LABEL)));
 
-    sender.clear();
-    requestScopeOperations.setApiUser(admin.id());
-    gApi.changes().id(r.getChangeId()).abandon();
-    List<Message> messages = sender.getMessages();
-    assertThat(messages).hasSize(1);
-    assertThat(messages.get(0).rcpt()).containsExactly(user2.getEmailAddress());
-    accountIndexedCounter.assertNoReindex();
+      sender.clear();
+      requestScopeOperations.setApiUser(admin.id());
+      gApi.changes().id(r.getChangeId()).abandon();
+      List<Message> messages = sender.getMessages();
+      assertThat(messages).hasSize(1);
+      assertThat(messages.get(0).rcpt()).containsExactly(user2.getEmailAddress());
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void addReviewerToIgnoredChange() throws Exception {
-    PushOneCommit.Result r = createChange();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      PushOneCommit.Result r = createChange();
 
-    requestScopeOperations.setApiUser(user.id());
-    gApi.accounts().self().setStars(r.getChangeId(), new StarsInput(ImmutableSet.of(IGNORE_LABEL)));
+      requestScopeOperations.setApiUser(user.id());
+      gApi.accounts()
+          .self()
+          .setStars(r.getChangeId(), new StarsInput(ImmutableSet.of(IGNORE_LABEL)));
 
-    sender.clear();
-    requestScopeOperations.setApiUser(admin.id());
+      sender.clear();
+      requestScopeOperations.setApiUser(admin.id());
 
-    AddReviewerInput in = new AddReviewerInput();
-    in.reviewer = user.email();
-    gApi.changes().id(r.getChangeId()).addReviewer(in);
-    List<Message> messages = sender.getMessages();
-    assertThat(messages).hasSize(1);
-    Message message = messages.get(0);
-    assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
-    assertMailReplyTo(message, admin.email());
-    accountIndexedCounter.assertNoReindex();
+      AddReviewerInput in = new AddReviewerInput();
+      in.reviewer = user.email();
+      gApi.changes().id(r.getChangeId()).addReviewer(in);
+      List<Message> messages = sender.getMessages();
+      assertThat(messages).hasSize(1);
+      Message message = messages.get(0);
+      assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
+      assertMailReplyTo(message, admin.email());
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void suggestAccounts() throws Exception {
-    String adminUsername = "admin";
-    List<AccountInfo> result = gApi.accounts().suggestAccounts().withQuery(adminUsername).get();
-    assertThat(result).hasSize(1);
-    assertThat(result.get(0).username).isEqualTo(adminUsername);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String adminUsername = "admin";
+      List<AccountInfo> result = gApi.accounts().suggestAccounts().withQuery(adminUsername).get();
+      assertThat(result).hasSize(1);
+      assertThat(result.get(0).username).isEqualTo(adminUsername);
 
-    List<AccountInfo> resultShortcutApi = gApi.accounts().suggestAccounts(adminUsername).get();
-    assertThat(resultShortcutApi).hasSize(result.size());
+      List<AccountInfo> resultShortcutApi = gApi.accounts().suggestAccounts(adminUsername).get();
+      assertThat(resultShortcutApi).hasSize(result.size());
 
-    List<AccountInfo> emptyResult = gApi.accounts().suggestAccounts("unknown").get();
-    assertThat(emptyResult).isEmpty();
-    accountIndexedCounter.assertNoReindex();
+      List<AccountInfo> emptyResult = gApi.accounts().suggestAccounts("unknown").get();
+      assertThat(emptyResult).isEmpty();
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
@@ -983,17 +1012,21 @@
 
   @Test
   public void addEmail() throws Exception {
-    List<String> emails = ImmutableList.of("new.email@example.com", "new.email@example.systems");
-    Set<String> currentEmails = getEmails();
-    for (String email : emails) {
-      assertThat(currentEmails).doesNotContain(email);
-      EmailInput input = newEmailInput(email);
-      gApi.accounts().self().addEmail(input);
-      accountIndexedCounter.assertReindexOf(admin);
-    }
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      List<String> emails = ImmutableList.of("new.email@example.com", "new.email@example.systems");
+      Set<String> currentEmails = getEmails();
+      for (String email : emails) {
+        assertThat(currentEmails).doesNotContain(email);
+        EmailInput input = newEmailInput(email);
+        gApi.accounts().self().addEmail(input);
+        accountIndexedCounter.assertReindexOf(admin);
+      }
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).containsAtLeastElementsIn(emails);
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).containsAtLeastElementsIn(emails);
+    }
   }
 
   @Test
@@ -1011,13 +1044,17 @@
 
             // Non-supported TLD  (see tlds-alpha-by-domain.txt)
             "new.email@example.africa");
-    for (String email : emails) {
-      EmailInput input = newEmailInput(email);
-      BadRequestException thrown =
-          assertThrows(BadRequestException.class, () -> gApi.accounts().self().addEmail(input));
-      assertWithMessage(email).that(thrown).hasMessageThat().isEqualTo("invalid email address");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      for (String email : emails) {
+        EmailInput input = newEmailInput(email);
+        BadRequestException thrown =
+            assertThrows(BadRequestException.class, () -> gApi.accounts().self().addEmail(input));
+        assertWithMessage(email).that(thrown).hasMessageThat().isEqualTo("invalid email address");
+      }
+      accountIndexedCounter.assertNoReindex();
     }
-    accountIndexedCounter.assertNoReindex();
   }
 
   @Test
@@ -1097,62 +1134,74 @@
 
   @Test
   public void addEmailAndSetPreferred() throws Exception {
-    String email = "foo.bar@example.com";
-    EmailInput input = new EmailInput();
-    input.email = email;
-    input.noConfirmation = true;
-    input.preferred = true;
-    gApi.accounts().self().addEmail(input);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String email = "foo.bar@example.com";
+      EmailInput input = new EmailInput();
+      input.email = email;
+      input.noConfirmation = true;
+      input.preferred = true;
+      gApi.accounts().self().addEmail(input);
 
-    // Account is reindexed twice; once on adding the new email,
-    // and then again on setting the email preferred.
-    accountIndexedCounter.assertReindexOf(admin, 2);
+      // Account is reindexed twice; once on adding the new email,
+      // and then again on setting the email preferred.
+      accountIndexedCounter.assertReindexOf(admin, 2);
 
-    String preferred = gApi.accounts().self().get().email;
-    assertThat(preferred).isEqualTo(email);
+      String preferred = gApi.accounts().self().get().email;
+      assertThat(preferred).isEqualTo(email);
+    }
   }
 
   @Test
   public void deleteEmail() throws Exception {
-    String email = "foo.bar@example.com";
-    EmailInput input = newEmailInput(email);
-    gApi.accounts().self().addEmail(input);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String email = "foo.bar@example.com";
+      EmailInput input = newEmailInput(email);
+      gApi.accounts().self().addEmail(input);
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).contains(email);
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).contains(email);
 
-    accountIndexedCounter.clear();
-    gApi.accounts().self().deleteEmail(input.email);
-    accountIndexedCounter.assertReindexOf(admin);
+      accountIndexedCounter.clear();
+      gApi.accounts().self().deleteEmail(input.email);
+      accountIndexedCounter.assertReindexOf(admin);
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).doesNotContain(email);
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).doesNotContain(email);
+    }
   }
 
   @Test
   public void deletePreferredEmail() throws Exception {
-    String previous = gApi.accounts().self().get().email;
-    String email = "foo.bar.baz@example.com";
-    EmailInput input = new EmailInput();
-    input.email = email;
-    input.noConfirmation = true;
-    input.preferred = true;
-    gApi.accounts().self().addEmail(input);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String previous = gApi.accounts().self().get().email;
+      String email = "foo.bar.baz@example.com";
+      EmailInput input = new EmailInput();
+      input.email = email;
+      input.noConfirmation = true;
+      input.preferred = true;
+      gApi.accounts().self().addEmail(input);
 
-    // Account is reindexed twice; once on adding the new email,
-    // and then again on setting the email preferred.
-    accountIndexedCounter.assertReindexOf(admin, 2);
+      // Account is reindexed twice; once on adding the new email,
+      // and then again on setting the email preferred.
+      accountIndexedCounter.assertReindexOf(admin, 2);
 
-    // The new preferred email is set
-    assertThat(gApi.accounts().self().get().email).isEqualTo(email);
+      // The new preferred email is set
+      assertThat(gApi.accounts().self().get().email).isEqualTo(email);
 
-    accountIndexedCounter.clear();
-    gApi.accounts().self().deleteEmail(input.email);
-    accountIndexedCounter.assertReindexOf(admin);
+      accountIndexedCounter.clear();
+      gApi.accounts().self().deleteEmail(input.email);
+      accountIndexedCounter.assertReindexOf(admin);
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).containsExactly(previous);
-    assertThat(gApi.accounts().self().get().email).isNull();
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).containsExactly(previous);
+      assertThat(gApi.accounts().self().get().email).isNull();
+    }
   }
 
   @Test
@@ -1178,64 +1227,77 @@
 
   @Test
   public void deleteEmailFromCustomExternalIdSchemes() throws Exception {
-    String email = "foo.bar@example.com";
-    String extId1 = "foo:bar";
-    String extId2 = "foo:baz";
-    accountsUpdateProvider
-        .get()
-        .update(
-            "Add External IDs",
-            admin.id(),
-            u ->
-                u.addExternalId(
-                        ExternalId.createWithEmail(ExternalId.Key.parse(extId1), admin.id(), email))
-                    .addExternalId(
-                        ExternalId.createWithEmail(
-                            ExternalId.Key.parse(extId2), admin.id(), email)));
-    accountIndexedCounter.assertReindexOf(admin);
-    assertThat(
-            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
-        .containsAtLeast(extId1, extId2);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String email = "foo.bar@example.com";
+      String extId1 = "foo:bar";
+      String extId2 = "foo:baz";
+      accountsUpdateProvider
+          .get()
+          .update(
+              "Add External IDs",
+              admin.id(),
+              u ->
+                  u.addExternalId(
+                          ExternalId.createWithEmail(
+                              ExternalId.Key.parse(extId1), admin.id(), email))
+                      .addExternalId(
+                          ExternalId.createWithEmail(
+                              ExternalId.Key.parse(extId2), admin.id(), email)));
+      accountIndexedCounter.assertReindexOf(admin);
+      assertThat(
+              gApi.accounts().self().getExternalIds().stream()
+                  .map(e -> e.identity)
+                  .collect(toSet()))
+          .containsAtLeast(extId1, extId2);
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).contains(email);
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).contains(email);
 
-    gApi.accounts().self().deleteEmail(email);
-    accountIndexedCounter.assertReindexOf(admin);
+      gApi.accounts().self().deleteEmail(email);
+      accountIndexedCounter.assertReindexOf(admin);
 
-    requestScopeOperations.resetCurrentApiUser();
-    assertThat(getEmails()).doesNotContain(email);
-    assertThat(
-            gApi.accounts().self().getExternalIds().stream().map(e -> e.identity).collect(toSet()))
-        .containsNoneOf(extId1, extId2);
+      requestScopeOperations.resetCurrentApiUser();
+      assertThat(getEmails()).doesNotContain(email);
+      assertThat(
+              gApi.accounts().self().getExternalIds().stream()
+                  .map(e -> e.identity)
+                  .collect(toSet()))
+          .containsNoneOf(extId1, extId2);
+    }
   }
 
   @Test
   public void deleteEmailOfOtherUser() throws Exception {
-    String email = "foo.bar@example.com";
-    EmailInput input = new EmailInput();
-    input.email = email;
-    input.noConfirmation = true;
-    gApi.accounts().id(user.id().get()).addEmail(input);
-    accountIndexedCounter.assertReindexOf(user);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String email = "foo.bar@example.com";
+      EmailInput input = new EmailInput();
+      input.email = email;
+      input.noConfirmation = true;
+      gApi.accounts().id(user.id().get()).addEmail(input);
+      accountIndexedCounter.assertReindexOf(user);
 
-    requestScopeOperations.setApiUser(user.id());
-    assertThat(getEmails()).contains(email);
+      requestScopeOperations.setApiUser(user.id());
+      assertThat(getEmails()).contains(email);
 
-    // admin can delete email of user
-    requestScopeOperations.setApiUser(admin.id());
-    gApi.accounts().id(user.id().get()).deleteEmail(email);
-    accountIndexedCounter.assertReindexOf(user);
+      // admin can delete email of user
+      requestScopeOperations.setApiUser(admin.id());
+      gApi.accounts().id(user.id().get()).deleteEmail(email);
+      accountIndexedCounter.assertReindexOf(user);
 
-    requestScopeOperations.setApiUser(user.id());
-    assertThat(getEmails()).doesNotContain(email);
+      requestScopeOperations.setApiUser(user.id());
+      assertThat(getEmails()).doesNotContain(email);
 
-    // user cannot delete email of admin
-    AuthException thrown =
-        assertThrows(
-            AuthException.class,
-            () -> gApi.accounts().id(admin.id().get()).deleteEmail(admin.email()));
-    assertThat(thrown).hasMessageThat().contains("modify account not permitted");
+      // user cannot delete email of admin
+      AuthException thrown =
+          assertThrows(
+              AuthException.class,
+              () -> gApi.accounts().id(admin.id().get()).deleteEmail(admin.email()));
+      assertThat(thrown).hasMessageThat().contains("modify account not permitted");
+    }
   }
 
   @Test
@@ -1301,17 +1363,21 @@
   public void putStatus() throws Exception {
     List<String> statuses = ImmutableList.of("OOO", "Busy");
     AccountInfo info;
-    for (String status : statuses) {
-      gApi.accounts().self().setStatus(status);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      for (String status : statuses) {
+        gApi.accounts().self().setStatus(status);
+        info = gApi.accounts().self().get();
+        assertUser(info, admin, status);
+        accountIndexedCounter.assertReindexOf(admin);
+      }
+
+      gApi.accounts().self().setStatus(null);
       info = gApi.accounts().self().get();
-      assertUser(info, admin, status);
+      assertUser(info, admin);
       accountIndexedCounter.assertReindexOf(admin);
     }
-
-    gApi.accounts().self().setStatus(null);
-    info = gApi.accounts().self().get();
-    assertUser(info, admin);
-    accountIndexedCounter.assertReindexOf(admin);
   }
 
   @Test
@@ -1347,61 +1413,65 @@
 
   @Test
   public void fetchUserBranch() throws Exception {
-    requestScopeOperations.setApiUser(user.id());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      requestScopeOperations.setApiUser(user.id());
 
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, user);
-    String userRefName = RefNames.refsUsers(user.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, user);
+      String userRefName = RefNames.refsUsers(user.id());
 
-    // remove default READ permissions
-    try (ProjectConfigUpdate u = updateProject(allUsers)) {
-      u.getConfig()
-          .getAccessSection(RefNames.REFS_USERS + "${" + RefPattern.USERID_SHARDED + "}", true)
-          .remove(new Permission(Permission.READ));
-      u.save();
+      // remove default READ permissions
+      try (ProjectConfigUpdate u = updateProject(allUsers)) {
+        u.getConfig()
+            .getAccessSection(RefNames.REFS_USERS + "${" + RefPattern.USERID_SHARDED + "}", true)
+            .remove(new Permission(Permission.READ));
+        u.save();
+      }
+
+      // deny READ permission that is inherited from All-Projects
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(deny(Permission.READ).ref(RefNames.REFS + "*").group(ANONYMOUS_USERS))
+          .update();
+
+      // fetching user branch without READ permission fails
+      assertThrows(TransportException.class, () -> fetch(allUsersRepo, userRefName + ":userRef"));
+
+      // allow each user to read its own user branch
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(
+              allow(Permission.READ)
+                  .ref(RefNames.REFS_USERS + "${" + RefPattern.USERID_SHARDED + "}")
+                  .group(REGISTERED_USERS))
+          .update();
+
+      // fetch user branch using refs/users/YY/XXXXXXX
+      fetch(allUsersRepo, userRefName + ":userRef");
+      Ref userRef = allUsersRepo.getRepository().exactRef("userRef");
+      assertThat(userRef).isNotNull();
+
+      // fetch user branch using refs/users/self
+      fetch(allUsersRepo, RefNames.REFS_USERS_SELF + ":userSelfRef");
+      Ref userSelfRef = allUsersRepo.getRepository().getRefDatabase().exactRef("userSelfRef");
+      assertThat(userSelfRef).isNotNull();
+      assertThat(userSelfRef.getObjectId()).isEqualTo(userRef.getObjectId());
+
+      accountIndexedCounter.assertNoReindex();
+
+      // fetching user branch of another user fails
+      String otherUserRefName = RefNames.refsUsers(admin.id());
+      TransportException thrown =
+          assertThrows(
+              TransportException.class,
+              () -> fetch(allUsersRepo, otherUserRefName + ":otherUserRef"));
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains("Remote does not have " + otherUserRefName + " available for fetch.");
     }
-
-    // deny READ permission that is inherited from All-Projects
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(deny(Permission.READ).ref(RefNames.REFS + "*").group(ANONYMOUS_USERS))
-        .update();
-
-    // fetching user branch without READ permission fails
-    assertThrows(TransportException.class, () -> fetch(allUsersRepo, userRefName + ":userRef"));
-
-    // allow each user to read its own user branch
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(
-            allow(Permission.READ)
-                .ref(RefNames.REFS_USERS + "${" + RefPattern.USERID_SHARDED + "}")
-                .group(REGISTERED_USERS))
-        .update();
-
-    // fetch user branch using refs/users/YY/XXXXXXX
-    fetch(allUsersRepo, userRefName + ":userRef");
-    Ref userRef = allUsersRepo.getRepository().exactRef("userRef");
-    assertThat(userRef).isNotNull();
-
-    // fetch user branch using refs/users/self
-    fetch(allUsersRepo, RefNames.REFS_USERS_SELF + ":userSelfRef");
-    Ref userSelfRef = allUsersRepo.getRepository().getRefDatabase().exactRef("userSelfRef");
-    assertThat(userSelfRef).isNotNull();
-    assertThat(userSelfRef.getObjectId()).isEqualTo(userRef.getObjectId());
-
-    accountIndexedCounter.assertNoReindex();
-
-    // fetching user branch of another user fails
-    String otherUserRefName = RefNames.refsUsers(admin.id());
-    TransportException thrown =
-        assertThrows(
-            TransportException.class,
-            () -> fetch(allUsersRepo, otherUserRefName + ":otherUserRef"));
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains("Remote does not have " + otherUserRefName + " available for fetch.");
   }
 
   @Test
@@ -1419,535 +1489,599 @@
 
   @Test
   public void pushToUserBranch() throws Exception {
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
-    PushOneCommit push = pushFactory.create(admin.newIdent(), allUsersRepo);
-    push.to(RefNames.refsUsers(admin.id())).assertOkStatus();
-    accountIndexedCounter.assertReindexOf(admin);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
+      PushOneCommit push = pushFactory.create(admin.newIdent(), allUsersRepo);
+      push.to(RefNames.refsUsers(admin.id())).assertOkStatus();
+      accountIndexedCounter.assertReindexOf(admin);
 
-    push = pushFactory.create(admin.newIdent(), allUsersRepo);
-    push.to(RefNames.REFS_USERS_SELF).assertOkStatus();
-    accountIndexedCounter.assertReindexOf(admin);
+      push = pushFactory.create(admin.newIdent(), allUsersRepo);
+      push.to(RefNames.REFS_USERS_SELF).assertOkStatus();
+      accountIndexedCounter.assertReindexOf(admin);
+    }
   }
 
   @Test
   public void pushToUserBranchForReview() throws Exception {
-    String userRefName = RefNames.refsUsers(admin.id());
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRefName + ":userRef");
-    allUsersRepo.reset("userRef");
-    PushOneCommit push = pushFactory.create(admin.newIdent(), allUsersRepo);
-    PushOneCommit.Result r = push.to(MagicBranch.NEW_CHANGE + userRefName);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRefName);
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    gApi.changes().id(r.getChangeId()).current().submit();
-    accountIndexedCounter.assertReindexOf(admin);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String userRefName = RefNames.refsUsers(admin.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRefName + ":userRef");
+      allUsersRepo.reset("userRef");
+      PushOneCommit push = pushFactory.create(admin.newIdent(), allUsersRepo);
+      PushOneCommit.Result r = push.to(MagicBranch.NEW_CHANGE + userRefName);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRefName);
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      gApi.changes().id(r.getChangeId()).current().submit();
+      accountIndexedCounter.assertReindexOf(admin);
 
-    push = pushFactory.create(admin.newIdent(), allUsersRepo);
-    r = push.to(MagicBranch.NEW_CHANGE + RefNames.REFS_USERS_SELF);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRefName);
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    gApi.changes().id(r.getChangeId()).current().submit();
-    accountIndexedCounter.assertReindexOf(admin);
+      push = pushFactory.create(admin.newIdent(), allUsersRepo);
+      r = push.to(MagicBranch.NEW_CHANGE + RefNames.REFS_USERS_SELF);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRefName);
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      gApi.changes().id(r.getChangeId()).current().submit();
+      accountIndexedCounter.assertReindexOf(admin);
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchForReviewAndSubmit() throws Exception {
-    String userRef = RefNames.refsUsers(admin.id());
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String userRef = RefNames.refsUsers(admin.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, "out-of-office");
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, "out-of-office");
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    gApi.changes().id(r.getChangeId()).current().submit();
-    accountIndexedCounter.assertReindexOf(admin);
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      gApi.changes().id(r.getChangeId()).current().submit();
+      accountIndexedCounter.assertReindexOf(admin);
 
-    AccountInfo info = gApi.accounts().self().get();
-    assertThat(info.email).isEqualTo(admin.email());
-    assertThat(info.name).isEqualTo(admin.fullName());
-    assertThat(info.status).isEqualTo("out-of-office");
+      AccountInfo info = gApi.accounts().self().get();
+      assertThat(info.email).isEqualTo(admin.email());
+      assertThat(info.name).isEqualTo(admin.fullName());
+      assertThat(info.status).isEqualTo("out-of-office");
+    }
   }
 
   @Test
   public void pushAccountConfigWithPrefEmailThatDoesNotExistAsExtIdToUserBranchForReviewAndSubmit()
       throws Exception {
-    TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
-    String userRef = RefNames.refsUsers(foo.id());
-    accountIndexedCounter.clear();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
+      String userRef = RefNames.refsUsers(foo.id());
+      accountIndexedCounter.clear();
 
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    String email = "some.email@example.com";
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, email);
+      String email = "some.email@example.com";
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, email);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                foo.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  foo.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    requestScopeOperations.setApiUser(foo.id());
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    gApi.changes().id(r.getChangeId()).current().submit();
+      requestScopeOperations.setApiUser(foo.id());
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      gApi.changes().id(r.getChangeId()).current().submit();
 
-    accountIndexedCounter.assertReindexOf(foo);
+      accountIndexedCounter.assertReindexOf(foo);
 
-    AccountInfo info = gApi.accounts().self().get();
-    assertThat(info.email).isEqualTo(email);
-    assertThat(info.name).isEqualTo(foo.fullName());
+      AccountInfo info = gApi.accounts().self().get();
+      assertThat(info.email).isEqualTo(email);
+      assertThat(info.name).isEqualTo(foo.fullName());
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchForReviewIsRejectedOnSubmitIfConfigIsInvalid()
       throws Exception {
-    String userRef = RefNames.refsUsers(admin.id());
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String userRef = RefNames.refsUsers(admin.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                "invalid config")
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  "invalid config")
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    ResourceConflictException thrown =
-        assertThrows(
-            ResourceConflictException.class,
-            () -> gApi.changes().id(r.getChangeId()).current().submit());
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains(
-            String.format(
-                "invalid account configuration: commit '%s' has an invalid '%s' file for account"
-                    + " '%s': Invalid config file %s in commit %s",
-                r.getCommit().name(),
-                AccountProperties.ACCOUNT_CONFIG,
-                admin.id(),
-                AccountProperties.ACCOUNT_CONFIG,
-                r.getCommit().name()));
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      ResourceConflictException thrown =
+          assertThrows(
+              ResourceConflictException.class,
+              () -> gApi.changes().id(r.getChangeId()).current().submit());
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains(
+              String.format(
+                  "invalid account configuration: commit '%s' has an invalid '%s' file for account"
+                      + " '%s': Invalid config file %s in commit %s",
+                  r.getCommit().name(),
+                  AccountProperties.ACCOUNT_CONFIG,
+                  admin.id(),
+                  AccountProperties.ACCOUNT_CONFIG,
+                  r.getCommit().name()));
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchForReviewIsRejectedOnSubmitIfPreferredEmailIsInvalid()
       throws Exception {
-    String userRef = RefNames.refsUsers(admin.id());
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String userRef = RefNames.refsUsers(admin.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    String noEmail = "no.email";
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, noEmail);
+      String noEmail = "no.email";
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, noEmail);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    ResourceConflictException thrown =
-        assertThrows(
-            ResourceConflictException.class,
-            () -> gApi.changes().id(r.getChangeId()).current().submit());
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains(
-            String.format(
-                "invalid account configuration: invalid preferred email '%s' for account '%s'",
-                noEmail, admin.id()));
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      ResourceConflictException thrown =
+          assertThrows(
+              ResourceConflictException.class,
+              () -> gApi.changes().id(r.getChangeId()).current().submit());
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains(
+              String.format(
+                  "invalid account configuration: invalid preferred email '%s' for account '%s'",
+                  noEmail, admin.id()));
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchForReviewIsRejectedOnSubmitIfOwnAccountIsDeactivated()
       throws Exception {
-    String userRef = RefNames.refsUsers(admin.id());
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      String userRef = RefNames.refsUsers(admin.id());
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    ResourceConflictException thrown =
-        assertThrows(
-            ResourceConflictException.class,
-            () -> gApi.changes().id(r.getChangeId()).current().submit());
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains("invalid account configuration: cannot deactivate own account");
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      ResourceConflictException thrown =
+          assertThrows(
+              ResourceConflictException.class,
+              () -> gApi.changes().id(r.getChangeId()).current().submit());
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains("invalid account configuration: cannot deactivate own account");
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchForReviewDeactivateOtherAccount() throws Exception {
-    projectOperations
-        .allProjectsForUpdate()
-        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
-        .update();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      projectOperations
+          .allProjectsForUpdate()
+          .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+          .update();
 
-    TestAccount foo = accountCreator.create(name("foo"));
-    assertThat(gApi.accounts().id(foo.id().get()).getActive()).isTrue();
-    String userRef = RefNames.refsUsers(foo.id());
-    accountIndexedCounter.clear();
+      TestAccount foo = accountCreator.create(name("foo"));
+      assertThat(gApi.accounts().id(foo.id().get()).getActive()).isTrue();
+      String userRef = RefNames.refsUsers(foo.id());
+      accountIndexedCounter.clear();
 
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
-        .add(allowLabel("Code-Review").ref(userRef).group(adminGroupUuid()).range(-2, 2))
-        .add(allow(Permission.SUBMIT).ref(userRef).group(adminGroupUuid()))
-        .update();
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
+          .add(allowLabel("Code-Review").ref(userRef).group(adminGroupUuid()).range(-2, 2))
+          .add(allow(Permission.SUBMIT).ref(userRef).group(adminGroupUuid()))
+          .update();
 
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(MagicBranch.NEW_CHANGE + userRef);
-    r.assertOkStatus();
-    accountIndexedCounter.assertNoReindex();
-    assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(MagicBranch.NEW_CHANGE + userRef);
+      r.assertOkStatus();
+      accountIndexedCounter.assertNoReindex();
+      assertThat(r.getChange().change().getDest().branch()).isEqualTo(userRef);
 
-    gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
-    gApi.changes().id(r.getChangeId()).current().submit();
-    accountIndexedCounter.assertReindexOf(foo);
+      gApi.changes().id(r.getChangeId()).current().review(ReviewInput.approve());
+      gApi.changes().id(r.getChangeId()).current().submit();
+      accountIndexedCounter.assertReindexOf(foo);
 
-    assertThat(gApi.accounts().id(foo.id().get()).getActive()).isFalse();
+      assertThat(gApi.accounts().id(foo.id().get()).getActive()).isFalse();
+    }
   }
 
   @Test
   public void pushWatchConfigToUserBranch() throws Exception {
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config wc = new Config();
-    wc.setString(
-        ProjectWatches.PROJECT,
-        project.get(),
-        ProjectWatches.KEY_NOTIFY,
-        ProjectWatches.NotifyValue.create(null, EnumSet.of(NotifyType.ALL_COMMENTS)).toString());
-    PushOneCommit push =
-        pushFactory.create(
-            admin.newIdent(),
-            allUsersRepo,
-            "Add project watch",
-            ProjectWatches.WATCH_CONFIG,
-            wc.toText());
-    push.to(RefNames.REFS_USERS_SELF).assertOkStatus();
-    accountIndexedCounter.assertReindexOf(admin);
+      Config wc = new Config();
+      wc.setString(
+          ProjectWatches.PROJECT,
+          project.get(),
+          ProjectWatches.KEY_NOTIFY,
+          ProjectWatches.NotifyValue.create(null, EnumSet.of(NotifyType.ALL_COMMENTS)).toString());
+      PushOneCommit push =
+          pushFactory.create(
+              admin.newIdent(),
+              allUsersRepo,
+              "Add project watch",
+              ProjectWatches.WATCH_CONFIG,
+              wc.toText());
+      push.to(RefNames.REFS_USERS_SELF).assertOkStatus();
+      accountIndexedCounter.assertReindexOf(admin);
 
-    String invalidNotifyValue = "]invalid[";
-    wc.setString(
-        ProjectWatches.PROJECT, project.get(), ProjectWatches.KEY_NOTIFY, invalidNotifyValue);
-    push =
-        pushFactory.create(
-            admin.newIdent(),
-            allUsersRepo,
-            "Add invalid project watch",
-            ProjectWatches.WATCH_CONFIG,
-            wc.toText());
-    PushOneCommit.Result r = push.to(RefNames.REFS_USERS_SELF);
-    r.assertErrorStatus("invalid account configuration");
-    r.assertMessage(
-        String.format(
-            "%s: Invalid project watch of account %d for project %s: %s",
-            ProjectWatches.WATCH_CONFIG, admin.id().get(), project.get(), invalidNotifyValue));
+      String invalidNotifyValue = "]invalid[";
+      wc.setString(
+          ProjectWatches.PROJECT, project.get(), ProjectWatches.KEY_NOTIFY, invalidNotifyValue);
+      push =
+          pushFactory.create(
+              admin.newIdent(),
+              allUsersRepo,
+              "Add invalid project watch",
+              ProjectWatches.WATCH_CONFIG,
+              wc.toText());
+      PushOneCommit.Result r = push.to(RefNames.REFS_USERS_SELF);
+      r.assertErrorStatus("invalid account configuration");
+      r.assertMessage(
+          String.format(
+              "%s: Invalid project watch of account %d for project %s: %s",
+              ProjectWatches.WATCH_CONFIG, admin.id().get(), project.get(), invalidNotifyValue));
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranch() throws Exception {
-    TestAccount oooUser = accountCreator.create("away", "away@mail.invalid", "Ambrose Way");
-    requestScopeOperations.setApiUser(oooUser.id());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount oooUser = accountCreator.create("away", "away@mail.invalid", "Ambrose Way");
+      requestScopeOperations.setApiUser(oooUser.id());
 
-    // Must clone as oooUser to ensure the push is allowed.
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, oooUser);
-    fetch(allUsersRepo, RefNames.refsUsers(oooUser.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
+      // Must clone as oooUser to ensure the push is allowed.
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, oooUser);
+      fetch(allUsersRepo, RefNames.refsUsers(oooUser.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, "out-of-office");
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, "out-of-office");
 
-    accountIndexedCounter.clear();
-    pushFactory
-        .create(
-            oooUser.newIdent(),
-            allUsersRepo,
-            "Update account config",
-            AccountProperties.ACCOUNT_CONFIG,
-            ac.toText())
-        .to(RefNames.refsUsers(oooUser.id()))
-        .assertOkStatus();
+      accountIndexedCounter.clear();
+      pushFactory
+          .create(
+              oooUser.newIdent(),
+              allUsersRepo,
+              "Update account config",
+              AccountProperties.ACCOUNT_CONFIG,
+              ac.toText())
+          .to(RefNames.refsUsers(oooUser.id()))
+          .assertOkStatus();
 
-    accountIndexedCounter.assertReindexOf(oooUser);
+      accountIndexedCounter.assertReindexOf(oooUser);
 
-    AccountInfo info = gApi.accounts().self().get();
-    assertThat(info.email).isEqualTo(oooUser.email());
-    assertThat(info.name).isEqualTo(oooUser.fullName());
-    assertThat(info.status).isEqualTo("out-of-office");
+      AccountInfo info = gApi.accounts().self().get();
+      assertThat(info.email).isEqualTo(oooUser.email());
+      assertThat(info.name).isEqualTo(oooUser.fullName());
+      assertThat(info.status).isEqualTo("out-of-office");
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchIsRejectedIfConfigIsInvalid() throws Exception {
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                "invalid config")
-            .to(RefNames.REFS_USERS_SELF);
-    r.assertErrorStatus("invalid account configuration");
-    r.assertMessage(
-        String.format(
-            "commit '%s' has an invalid '%s' file for account '%s':"
-                + " Invalid config file %s in commit %s",
-            r.getCommit().name(),
-            AccountProperties.ACCOUNT_CONFIG,
-            admin.id(),
-            AccountProperties.ACCOUNT_CONFIG,
-            r.getCommit().name()));
-    accountIndexedCounter.assertNoReindex();
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  "invalid config")
+              .to(RefNames.REFS_USERS_SELF);
+      r.assertErrorStatus("invalid account configuration");
+      r.assertMessage(
+          String.format(
+              "commit '%s' has an invalid '%s' file for account '%s':"
+                  + " Invalid config file %s in commit %s",
+              r.getCommit().name(),
+              AccountProperties.ACCOUNT_CONFIG,
+              admin.id(),
+              AccountProperties.ACCOUNT_CONFIG,
+              r.getCommit().name()));
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchIsRejectedIfPreferredEmailIsInvalid() throws Exception {
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    String noEmail = "no.email";
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, noEmail);
+      String noEmail = "no.email";
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, noEmail);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(RefNames.REFS_USERS_SELF);
-    r.assertErrorStatus("invalid account configuration");
-    r.assertMessage(
-        String.format("invalid preferred email '%s' for account '%s'", noEmail, admin.id()));
-    accountIndexedCounter.assertNoReindex();
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(RefNames.REFS_USERS_SELF);
+      r.assertErrorStatus("invalid account configuration");
+      r.assertMessage(
+          String.format("invalid preferred email '%s' for account '%s'", noEmail, admin.id()));
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchInvalidPreferredEmailButNotChanged() throws Exception {
-    TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
-    String userRef = RefNames.refsUsers(foo.id());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
+      String userRef = RefNames.refsUsers(foo.id());
 
-    String noEmail = "no.email";
-    accountsUpdateProvider
-        .get()
-        .update("Set Preferred Email", foo.id(), u -> u.setPreferredEmail(noEmail));
-    accountIndexedCounter.clear();
+      String noEmail = "no.email";
+      accountsUpdateProvider
+          .get()
+          .update("Set Preferred Email", foo.id(), u -> u.setPreferredEmail(noEmail));
+      accountIndexedCounter.clear();
 
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(allow(Permission.PUSH).ref(userRef).group(REGISTERED_USERS))
-        .update();
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(allow(Permission.PUSH).ref(userRef).group(REGISTERED_USERS))
+          .update();
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    String status = "in vacation";
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, status);
+      String status = "in vacation";
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_STATUS, status);
 
-    pushFactory
-        .create(
-            foo.newIdent(),
-            allUsersRepo,
-            "Update account config",
-            AccountProperties.ACCOUNT_CONFIG,
-            ac.toText())
-        .to(userRef)
-        .assertOkStatus();
-    accountIndexedCounter.assertReindexOf(foo);
+      pushFactory
+          .create(
+              foo.newIdent(),
+              allUsersRepo,
+              "Update account config",
+              AccountProperties.ACCOUNT_CONFIG,
+              ac.toText())
+          .to(userRef)
+          .assertOkStatus();
+      accountIndexedCounter.assertReindexOf(foo);
 
-    AccountInfo info = gApi.accounts().id(foo.id().get()).get();
-    assertThat(info.email).isEqualTo(noEmail);
-    assertThat(info.name).isEqualTo(foo.fullName());
-    assertThat(info.status).isEqualTo(status);
+      AccountInfo info = gApi.accounts().id(foo.id().get()).get();
+      assertThat(info.email).isEqualTo(noEmail);
+      assertThat(info.name).isEqualTo(foo.fullName());
+      assertThat(info.status).isEqualTo(status);
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchIfPreferredEmailDoesNotExistAsExtId() throws Exception {
-    TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
-    String userRef = RefNames.refsUsers(foo.id());
-    accountIndexedCounter.clear();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestAccount foo = accountCreator.create(name("foo"), name("foo") + "@example.com", "Foo");
+      String userRef = RefNames.refsUsers(foo.id());
+      accountIndexedCounter.clear();
 
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
-        .update();
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
+          .update();
 
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, foo);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    String email = "some.email@example.com";
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, email);
+      String email = "some.email@example.com";
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setString(AccountProperties.ACCOUNT, null, AccountProperties.KEY_PREFERRED_EMAIL, email);
 
-    pushFactory
-        .create(
-            foo.newIdent(),
-            allUsersRepo,
-            "Update account config",
-            AccountProperties.ACCOUNT_CONFIG,
-            ac.toText())
-        .to(userRef)
-        .assertOkStatus();
-    accountIndexedCounter.assertReindexOf(foo);
+      pushFactory
+          .create(
+              foo.newIdent(),
+              allUsersRepo,
+              "Update account config",
+              AccountProperties.ACCOUNT_CONFIG,
+              ac.toText())
+          .to(userRef)
+          .assertOkStatus();
+      accountIndexedCounter.assertReindexOf(foo);
 
-    AccountInfo info = gApi.accounts().id(foo.id().get()).get();
-    assertThat(info.email).isEqualTo(email);
-    assertThat(info.name).isEqualTo(foo.fullName());
+      AccountInfo info = gApi.accounts().id(foo.id().get()).get();
+      assertThat(info.email).isEqualTo(email);
+      assertThat(info.name).isEqualTo(foo.fullName());
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchIsRejectedIfOwnAccountIsDeactivated() throws Exception {
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
-    allUsersRepo.reset("userRef");
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, RefNames.refsUsers(admin.id()) + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
 
-    PushOneCommit.Result r =
-        pushFactory
-            .create(
-                admin.newIdent(),
-                allUsersRepo,
-                "Update account config",
-                AccountProperties.ACCOUNT_CONFIG,
-                ac.toText())
-            .to(RefNames.REFS_USERS_SELF);
-    r.assertErrorStatus("invalid account configuration");
-    r.assertMessage("cannot deactivate own account");
-    accountIndexedCounter.assertNoReindex();
+      PushOneCommit.Result r =
+          pushFactory
+              .create(
+                  admin.newIdent(),
+                  allUsersRepo,
+                  "Update account config",
+                  AccountProperties.ACCOUNT_CONFIG,
+                  ac.toText())
+              .to(RefNames.REFS_USERS_SELF);
+      r.assertErrorStatus("invalid account configuration");
+      r.assertMessage("cannot deactivate own account");
+      accountIndexedCounter.assertNoReindex();
+    }
   }
 
   @Test
   public void pushAccountConfigToUserBranchDeactivateOtherAccount() throws Exception {
-    projectOperations
-        .allProjectsForUpdate()
-        .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
-        .update();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      projectOperations
+          .allProjectsForUpdate()
+          .add(allowCapability(GlobalCapability.ACCESS_DATABASE).group(REGISTERED_USERS))
+          .update();
 
-    TestAccount foo = accountCreator.create(name("foo"));
-    assertThat(gApi.accounts().id(foo.id().get()).getActive()).isTrue();
-    String userRef = RefNames.refsUsers(foo.id());
-    accountIndexedCounter.clear();
+      TestAccount foo = accountCreator.create(name("foo"));
+      assertThat(gApi.accounts().id(foo.id().get()).getActive()).isTrue();
+      String userRef = RefNames.refsUsers(foo.id());
+      accountIndexedCounter.clear();
 
-    projectOperations
-        .project(allUsers)
-        .forUpdate()
-        .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
-        .update();
+      projectOperations
+          .project(allUsers)
+          .forUpdate()
+          .add(allow(Permission.PUSH).ref(userRef).group(adminGroupUuid()))
+          .update();
 
-    TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
-    fetch(allUsersRepo, userRef + ":userRef");
-    allUsersRepo.reset("userRef");
+      TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
+      fetch(allUsersRepo, userRef + ":userRef");
+      allUsersRepo.reset("userRef");
 
-    Config ac = getAccountConfig(allUsersRepo);
-    ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
+      Config ac = getAccountConfig(allUsersRepo);
+      ac.setBoolean(AccountProperties.ACCOUNT, null, AccountProperties.KEY_ACTIVE, false);
 
-    pushFactory
-        .create(
-            admin.newIdent(),
-            allUsersRepo,
-            "Update account config",
-            AccountProperties.ACCOUNT_CONFIG,
-            ac.toText())
-        .to(userRef)
-        .assertOkStatus();
-    accountIndexedCounter.assertReindexOf(foo);
+      pushFactory
+          .create(
+              admin.newIdent(),
+              allUsersRepo,
+              "Update account config",
+              AccountProperties.ACCOUNT_CONFIG,
+              ac.toText())
+          .to(userRef)
+          .assertOkStatus();
+      accountIndexedCounter.assertReindexOf(foo);
 
-    assertThat(gApi.accounts().id(foo.id().get()).getActive()).isFalse();
+      assertThat(gApi.accounts().id(foo.id().get()).getActive()).isFalse();
+    }
   }
 
   @Test
@@ -2150,103 +2284,127 @@
 
   @Test
   public void addOtherUsersGpgKey_Conflict() throws Exception {
-    // Both users have a matching external ID for this key.
-    addExternalIdEmail(admin, "test5@example.com");
-    accountsUpdateProvider
-        .get()
-        .update(
-            "Add External ID",
-            user.id(),
-            u -> u.addExternalId(ExternalId.create("foo", "myId", user.id())));
-    accountIndexedCounter.assertReindexOf(user);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      // Both users have a matching external ID for this key.
+      addExternalIdEmail(admin, "test5@example.com");
+      accountIndexedCounter.clear();
+      accountsUpdateProvider
+          .get()
+          .update(
+              "Add External ID",
+              user.id(),
+              u -> u.addExternalId(ExternalId.create("foo", "myId", user.id())));
+      accountIndexedCounter.assertReindexOf(user);
 
-    TestKey key = validKeyWithSecondUserId();
-    addGpgKey(key.getPublicKeyArmored());
-    requestScopeOperations.setApiUser(user.id());
+      TestKey key = validKeyWithSecondUserId();
+      addGpgKey(key.getPublicKeyArmored());
+      requestScopeOperations.setApiUser(user.id());
 
-    ResourceConflictException thrown =
-        assertThrows(
-            ResourceConflictException.class, () -> addGpgKey(user, key.getPublicKeyArmored()));
-    assertThat(thrown).hasMessageThat().contains("GPG key already associated with another account");
+      ResourceConflictException thrown =
+          assertThrows(
+              ResourceConflictException.class, () -> addGpgKey(user, key.getPublicKeyArmored()));
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains("GPG key already associated with another account");
+    }
   }
 
   @Test
   public void listGpgKeys() throws Exception {
-    List<TestKey> keys = allValidKeys();
-    List<String> toAdd = new ArrayList<>(keys.size());
-    for (TestKey key : keys) {
-      addExternalIdEmail(admin, PushCertificateIdent.parse(key.getFirstUserId()).getEmailAddress());
-      toAdd.add(key.getPublicKeyArmored());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      List<TestKey> keys = allValidKeys();
+      List<String> toAdd = new ArrayList<>(keys.size());
+      for (TestKey key : keys) {
+        addExternalIdEmail(
+            admin, PushCertificateIdent.parse(key.getFirstUserId()).getEmailAddress());
+        toAdd.add(key.getPublicKeyArmored());
+      }
+      accountIndexedCounter.clear();
+      gApi.accounts().self().putGpgKeys(toAdd, ImmutableList.of());
+      assertKeys(keys);
+      accountIndexedCounter.assertReindexOf(admin);
     }
-    gApi.accounts().self().putGpgKeys(toAdd, ImmutableList.of());
-    assertKeys(keys);
-    accountIndexedCounter.assertReindexOf(admin);
   }
 
   @Test
   public void deleteGpgKey() throws Exception {
-    TestKey key = validKeyWithoutExpiration();
-    String id = key.getKeyIdString();
-    addExternalIdEmail(admin, "test1@example.com");
-    addGpgKey(key.getPublicKeyArmored());
-    assertKeys(key);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      TestKey key = validKeyWithoutExpiration();
+      String id = key.getKeyIdString();
+      addExternalIdEmail(admin, "test1@example.com");
+      addGpgKey(key.getPublicKeyArmored());
+      assertKeys(key);
+      accountIndexedCounter.clear();
 
-    sender.clear();
-    gApi.accounts().self().gpgKey(id).delete();
-    accountIndexedCounter.assertReindexOf(admin);
-    assertKeys();
-    assertThat(sender.getMessages()).hasSize(1);
-    assertThat(sender.getMessages().get(0).body()).contains("GPG keys have been deleted");
+      sender.clear();
+      gApi.accounts().self().gpgKey(id).delete();
+      accountIndexedCounter.assertReindexOf(admin);
+      assertKeys();
+      assertThat(sender.getMessages()).hasSize(1);
+      assertThat(sender.getMessages().get(0).body()).contains("GPG keys have been deleted");
 
-    ResourceNotFoundException thrown =
-        assertThrows(
-            ResourceNotFoundException.class, () -> gApi.accounts().self().gpgKey(id).get());
-    assertThat(thrown).hasMessageThat().contains(id);
+      ResourceNotFoundException thrown =
+          assertThrows(
+              ResourceNotFoundException.class, () -> gApi.accounts().self().gpgKey(id).get());
+      assertThat(thrown).hasMessageThat().contains(id);
+    }
   }
 
   @Test
   public void addAndRemoveGpgKeys() throws Exception {
-    for (TestKey key : allValidKeys()) {
-      addExternalIdEmail(admin, PushCertificateIdent.parse(key.getFirstUserId()).getEmailAddress());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      for (TestKey key : allValidKeys()) {
+        addExternalIdEmail(
+            admin, PushCertificateIdent.parse(key.getFirstUserId()).getEmailAddress());
+      }
+      accountIndexedCounter.clear();
+      TestKey key1 = validKeyWithoutExpiration();
+      TestKey key2 = validKeyWithExpiration();
+      TestKey key5 = validKeyWithSecondUserId();
+
+      Map<String, GpgKeyInfo> infos =
+          gApi.accounts()
+              .self()
+              .putGpgKeys(
+                  ImmutableList.of(key1.getPublicKeyArmored(), key2.getPublicKeyArmored()),
+                  ImmutableList.of(key5.getKeyIdString()));
+      assertThat(infos.keySet()).containsExactly(key1.getKeyIdString(), key2.getKeyIdString());
+      assertKeys(key1, key2);
+      accountIndexedCounter.assertReindexOf(admin);
+
+      infos =
+          gApi.accounts()
+              .self()
+              .putGpgKeys(
+                  ImmutableList.of(key5.getPublicKeyArmored()),
+                  ImmutableList.of(key1.getKeyIdString()));
+      assertThat(infos.keySet()).containsExactly(key1.getKeyIdString(), key5.getKeyIdString());
+      assertKeyMapContains(key5, infos);
+      assertThat(infos.get(key1.getKeyIdString()).key).isNull();
+      assertKeys(key2, key5);
+      accountIndexedCounter.assertReindexOf(admin);
+
+      BadRequestException thrown =
+          assertThrows(
+              BadRequestException.class,
+              () ->
+                  gApi.accounts()
+                      .self()
+                      .putGpgKeys(
+                          ImmutableList.of(key2.getPublicKeyArmored()),
+                          ImmutableList.of(key2.getKeyIdString())));
+      assertThat(thrown)
+          .hasMessageThat()
+          .contains("Cannot both add and delete key: " + keyToString(key2.getPublicKey()));
     }
-    TestKey key1 = validKeyWithoutExpiration();
-    TestKey key2 = validKeyWithExpiration();
-    TestKey key5 = validKeyWithSecondUserId();
-
-    Map<String, GpgKeyInfo> infos =
-        gApi.accounts()
-            .self()
-            .putGpgKeys(
-                ImmutableList.of(key1.getPublicKeyArmored(), key2.getPublicKeyArmored()),
-                ImmutableList.of(key5.getKeyIdString()));
-    assertThat(infos.keySet()).containsExactly(key1.getKeyIdString(), key2.getKeyIdString());
-    assertKeys(key1, key2);
-    accountIndexedCounter.assertReindexOf(admin);
-
-    infos =
-        gApi.accounts()
-            .self()
-            .putGpgKeys(
-                ImmutableList.of(key5.getPublicKeyArmored()),
-                ImmutableList.of(key1.getKeyIdString()));
-    assertThat(infos.keySet()).containsExactly(key1.getKeyIdString(), key5.getKeyIdString());
-    assertKeyMapContains(key5, infos);
-    assertThat(infos.get(key1.getKeyIdString()).key).isNull();
-    assertKeys(key2, key5);
-    accountIndexedCounter.assertReindexOf(admin);
-
-    BadRequestException thrown =
-        assertThrows(
-            BadRequestException.class,
-            () ->
-                gApi.accounts()
-                    .self()
-                    .putGpgKeys(
-                        ImmutableList.of(key2.getPublicKeyArmored()),
-                        ImmutableList.of(key2.getKeyIdString())));
-    assertThat(thrown)
-        .hasMessageThat()
-        .contains("Cannot both add and delete key: " + keyToString(key2.getPublicKey()));
   }
 
   @Test
@@ -2259,110 +2417,118 @@
   @Test
   @UseSsh
   public void sshKeys() throws Exception {
-    // The test account should initially have exactly one ssh key
-    List<SshKeyInfo> info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(1);
-    assertSequenceNumbers(info);
-    SshKeyInfo key = info.get(0);
-    KeyPair keyPair = sshKeys.getKeyPair(admin);
-    String initial = TestSshKeys.publicKey(keyPair, admin.email());
-    assertThat(key.sshPublicKey).isEqualTo(initial);
-    accountIndexedCounter.assertNoReindex();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      // The test account should initially have exactly one ssh key
+      List<SshKeyInfo> info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(1);
+      assertSequenceNumbers(info);
+      SshKeyInfo key = info.get(0);
+      KeyPair keyPair = sshKeys.getKeyPair(admin);
+      String initial = TestSshKeys.publicKey(keyPair, admin.email());
+      assertThat(key.sshPublicKey).isEqualTo(initial);
+      accountIndexedCounter.assertNoReindex();
 
-    // Add a new key
-    sender.clear();
-    String newKey = TestSshKeys.publicKey(TestSshKeys.genSshKey(), admin.email());
-    gApi.accounts().self().addSshKey(newKey);
-    info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(2);
-    assertSequenceNumbers(info);
-    accountIndexedCounter.assertReindexOf(admin);
-    assertThat(sender.getMessages()).hasSize(1);
-    assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
+      // Add a new key
+      sender.clear();
+      String newKey = TestSshKeys.publicKey(TestSshKeys.genSshKey(), admin.email());
+      gApi.accounts().self().addSshKey(newKey);
+      info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(2);
+      assertSequenceNumbers(info);
+      accountIndexedCounter.assertReindexOf(admin);
+      assertThat(sender.getMessages()).hasSize(1);
+      assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
 
-    // Add an existing key (the request succeeds, but the key isn't added again)
-    sender.clear();
-    gApi.accounts().self().addSshKey(initial);
-    info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(2);
-    assertSequenceNumbers(info);
-    accountIndexedCounter.assertNoReindex();
-    // TODO: Issue 10769: Adding an already existing key should not result in a notification email
-    assertThat(sender.getMessages()).hasSize(1);
-    assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
+      // Add an existing key (the request succeeds, but the key isn't added again)
+      sender.clear();
+      gApi.accounts().self().addSshKey(initial);
+      info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(2);
+      assertSequenceNumbers(info);
+      accountIndexedCounter.assertNoReindex();
+      // TODO: Issue 10769: Adding an already existing key should not result in a notification email
+      assertThat(sender.getMessages()).hasSize(1);
+      assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
 
-    // Add another new key
-    sender.clear();
-    String newKey2 = TestSshKeys.publicKey(TestSshKeys.genSshKey(), admin.email());
-    gApi.accounts().self().addSshKey(newKey2);
-    info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(3);
-    assertSequenceNumbers(info);
-    accountIndexedCounter.assertReindexOf(admin);
-    assertThat(sender.getMessages()).hasSize(1);
-    assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
+      // Add another new key
+      sender.clear();
+      String newKey2 = TestSshKeys.publicKey(TestSshKeys.genSshKey(), admin.email());
+      gApi.accounts().self().addSshKey(newKey2);
+      info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(3);
+      assertSequenceNumbers(info);
+      accountIndexedCounter.assertReindexOf(admin);
+      assertThat(sender.getMessages()).hasSize(1);
+      assertThat(sender.getMessages().get(0).body()).contains("new SSH keys have been added");
 
-    // Delete second key
-    sender.clear();
-    gApi.accounts().self().deleteSshKey(2);
-    info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(2);
-    assertThat(info.get(0).seq).isEqualTo(1);
-    assertThat(info.get(1).seq).isEqualTo(3);
-    accountIndexedCounter.assertReindexOf(admin);
+      // Delete second key
+      sender.clear();
+      gApi.accounts().self().deleteSshKey(2);
+      info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(2);
+      assertThat(info.get(0).seq).isEqualTo(1);
+      assertThat(info.get(1).seq).isEqualTo(3);
+      accountIndexedCounter.assertReindexOf(admin);
 
-    assertThat(sender.getMessages()).hasSize(1);
-    assertThat(sender.getMessages().get(0).body()).contains("SSH keys have been deleted");
+      assertThat(sender.getMessages()).hasSize(1);
+      assertThat(sender.getMessages().get(0).body()).contains("SSH keys have been deleted");
 
-    // Mark first key as invalid
-    assertThat(info.get(0).valid).isTrue();
-    authorizedKeys.markKeyInvalid(admin.id(), 1);
-    info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(2);
-    assertThat(info.get(0).seq).isEqualTo(1);
-    assertThat(info.get(0).valid).isFalse();
-    assertThat(info.get(1).seq).isEqualTo(3);
-    accountIndexedCounter.assertReindexOf(admin);
+      // Mark first key as invalid
+      assertThat(info.get(0).valid).isTrue();
+      authorizedKeys.markKeyInvalid(admin.id(), 1);
+      info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(2);
+      assertThat(info.get(0).seq).isEqualTo(1);
+      assertThat(info.get(0).valid).isFalse();
+      assertThat(info.get(1).seq).isEqualTo(3);
+      accountIndexedCounter.assertReindexOf(admin);
+    }
   }
 
   @Test
   @UseSsh
   public void adminCanAddOrRemoveSshKeyOnOtherAccount() throws Exception {
-    // The test account should initially have exactly one ssh key
-    List<SshKeyInfo> info = gApi.accounts().self().listSshKeys();
-    assertThat(info).hasSize(1);
-    assertSequenceNumbers(info);
-    SshKeyInfo key = info.get(0);
-    KeyPair keyPair = sshKeys.getKeyPair(admin);
-    String initial = TestSshKeys.publicKey(keyPair, admin.email());
-    assertThat(key.sshPublicKey).isEqualTo(initial);
-    accountIndexedCounter.assertNoReindex();
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      // The test account should initially have exactly one ssh key
+      List<SshKeyInfo> info = gApi.accounts().self().listSshKeys();
+      assertThat(info).hasSize(1);
+      assertSequenceNumbers(info);
+      SshKeyInfo key = info.get(0);
+      KeyPair keyPair = sshKeys.getKeyPair(admin);
+      String initial = TestSshKeys.publicKey(keyPair, admin.email());
+      assertThat(key.sshPublicKey).isEqualTo(initial);
+      accountIndexedCounter.assertNoReindex();
 
-    // Add a new key
-    sender.clear();
-    String newKey = TestSshKeys.publicKey(TestSshKeys.genSshKey(), user.email());
-    gApi.accounts().id(user.username()).addSshKey(newKey);
-    info = gApi.accounts().id(user.username()).listSshKeys();
-    assertThat(info).hasSize(2);
-    assertSequenceNumbers(info);
-    accountIndexedCounter.assertReindexOf(user);
+      // Add a new key
+      sender.clear();
+      String newKey = TestSshKeys.publicKey(TestSshKeys.genSshKey(), user.email());
+      gApi.accounts().id(user.username()).addSshKey(newKey);
+      info = gApi.accounts().id(user.username()).listSshKeys();
+      assertThat(info).hasSize(2);
+      assertSequenceNumbers(info);
+      accountIndexedCounter.assertReindexOf(user);
 
-    assertThat(sender.getMessages()).hasSize(1);
-    Message message = sender.getMessages().get(0);
-    assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
-    assertThat(message.body()).contains("new SSH keys have been added");
+      assertThat(sender.getMessages()).hasSize(1);
+      Message message = sender.getMessages().get(0);
+      assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
+      assertThat(message.body()).contains("new SSH keys have been added");
 
-    // Delete key
-    sender.clear();
-    gApi.accounts().id(user.username()).deleteSshKey(1);
-    info = gApi.accounts().id(user.username()).listSshKeys();
-    assertThat(info).hasSize(1);
-    accountIndexedCounter.assertReindexOf(user);
+      // Delete key
+      sender.clear();
+      gApi.accounts().id(user.username()).deleteSshKey(1);
+      info = gApi.accounts().id(user.username()).listSshKeys();
+      assertThat(info).hasSize(1);
+      accountIndexedCounter.assertReindexOf(user);
 
-    assertThat(sender.getMessages()).hasSize(1);
-    message = sender.getMessages().get(0);
-    assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
-    assertThat(message.body()).contains("SSH keys have been deleted");
+      assertThat(sender.getMessages()).hasSize(1);
+      message = sender.getMessages().get(0);
+      assertThat(message.rcpt()).containsExactly(user.getEmailAddress());
+      assertThat(message.body()).contains("SSH keys have been deleted");
+    }
   }
 
   @Test
@@ -2385,20 +2551,24 @@
   // reindex is tested by {@link AbstractQueryAccountsTest#reindex}
   @Test
   public void reindexPermissions() throws Exception {
-    // admin can reindex any account
-    requestScopeOperations.setApiUser(admin.id());
-    gApi.accounts().id(user.username()).index();
-    accountIndexedCounter.assertReindexOf(user);
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      // admin can reindex any account
+      requestScopeOperations.setApiUser(admin.id());
+      gApi.accounts().id(user.username()).index();
+      accountIndexedCounter.assertReindexOf(user);
 
-    // user can reindex own account
-    requestScopeOperations.setApiUser(user.id());
-    gApi.accounts().self().index();
-    accountIndexedCounter.assertReindexOf(user);
+      // user can reindex own account
+      requestScopeOperations.setApiUser(user.id());
+      gApi.accounts().self().index();
+      accountIndexedCounter.assertReindexOf(user);
 
-    // user cannot reindex any account
-    AuthException thrown =
-        assertThrows(AuthException.class, () -> gApi.accounts().id(admin.username()).index());
-    assertThat(thrown).hasMessageThat().contains("modify account not permitted");
+      // user cannot reindex any account
+      AuthException thrown =
+          assertThrows(AuthException.class, () -> gApi.accounts().id(admin.username()).index());
+      assertThat(thrown).hasMessageThat().contains("modify account not permitted");
+    }
   }
 
   @Test
@@ -3266,17 +3436,21 @@
   }
 
   private void addExternalIdEmail(TestAccount account, String email) throws Exception {
-    requireNonNull(email);
-    accountsUpdateProvider
-        .get()
-        .update(
-            "Add Email",
-            account.id(),
-            u ->
-                u.addExternalId(
-                    ExternalId.createWithEmail(name("test"), email, account.id(), email)));
-    accountIndexedCounter.assertReindexOf(account);
-    requestScopeOperations.setApiUser(account.id());
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      requireNonNull(email);
+      accountsUpdateProvider
+          .get()
+          .update(
+              "Add Email",
+              account.id(),
+              u ->
+                  u.addExternalId(
+                      ExternalId.createWithEmail(name("test"), email, account.id(), email)));
+      accountIndexedCounter.assertReindexOf(account);
+      requestScopeOperations.setApiUser(account.id());
+    }
   }
 
   private Map<String, GpgKeyInfo> addGpgKey(String armored) throws Exception {
@@ -3284,12 +3458,16 @@
   }
 
   private Map<String, GpgKeyInfo> addGpgKey(TestAccount account, String armored) throws Exception {
-    Map<String, GpgKeyInfo> gpgKeys =
-        gApi.accounts()
-            .id(account.username())
-            .putGpgKeys(ImmutableList.of(armored), ImmutableList.<String>of());
-    accountIndexedCounter.assertReindexOf(gApi.accounts().id(account.username()).get());
-    return gpgKeys;
+    AccountIndexedCounter accountIndexedCounter = new AccountIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(accountIndexedCounter)) {
+      Map<String, GpgKeyInfo> gpgKeys =
+          gApi.accounts()
+              .id(account.username())
+              .putGpgKeys(ImmutableList.of(armored), ImmutableList.<String>of());
+      accountIndexedCounter.assertReindexOf(gApi.accounts().id(account.username()).get());
+      return gpgKeys;
+    }
   }
 
   private Map<String, GpgKeyInfo> addGpgKeyNoReindex(String armored) throws Exception {
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index 70d5e99..9767e08 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -161,6 +161,7 @@
 import com.google.gerrit.server.ChangeUtil;
 import com.google.gerrit.server.StarredChangesUtil;
 import com.google.gerrit.server.change.ChangeResource;
+import com.google.gerrit.server.change.testing.TestChangeETagComputation;
 import com.google.gerrit.server.group.SystemGroupBackend;
 import com.google.gerrit.server.index.change.ChangeIndex;
 import com.google.gerrit.server.index.change.ChangeIndexCollection;
@@ -2256,7 +2257,8 @@
     PushOneCommit.Result r = createChange();
     String oldETag = parseResource(r).getETag();
 
-    try (Registration registration = extensionRegistry.newRegistration().add((p, id) -> "foo")) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(TestChangeETagComputation.withETag("foo"))) {
       assertThat(parseResource(r).getETag()).isNotEqualTo(oldETag);
     }
 
@@ -2268,7 +2270,8 @@
     PushOneCommit.Result r = createChange();
     String oldETag = parseResource(r).getETag();
 
-    try (Registration registration = extensionRegistry.newRegistration().add((p, id) -> null)) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(TestChangeETagComputation.withETag(null))) {
       assertThat(parseResource(r).getETag()).isEqualTo(oldETag);
     }
   }
@@ -2282,9 +2285,8 @@
         extensionRegistry
             .newRegistration()
             .add(
-                (p, id) -> {
-                  throw new StorageException("exception during test");
-                })) {
+                TestChangeETagComputation.withException(
+                    new StorageException("exception during test")))) {
       assertThat(parseResource(r).getETag()).isEqualTo(oldETag);
     }
   }
diff --git a/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java b/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
index 599a2b9..ba8bb7a 100644
--- a/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/group/GroupsIT.java
@@ -38,6 +38,8 @@
 import com.google.common.truth.Correspondence;
 import com.google.common.util.concurrent.AtomicLongMap;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.GitUtil;
 import com.google.gerrit.acceptance.NoHttpd;
@@ -66,8 +68,6 @@
 import com.google.gerrit.extensions.common.GroupInfo;
 import com.google.gerrit.extensions.common.GroupOptionsInfo;
 import com.google.gerrit.extensions.events.GroupIndexedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
@@ -127,7 +127,6 @@
 public class GroupsIT extends AbstractDaemonTest {
   @Inject @ServerInitiated private GroupsUpdate groupsUpdate;
   @Inject private AccountOperations accountOperations;
-  @Inject private DynamicSet<GroupIndexedListener> groupIndexedListeners;
   @Inject private GroupIncludeCache groupIncludeCache;
   @Inject private GroupIndexer groupIndexer;
   @Inject private GroupOperations groupOperations;
@@ -138,6 +137,7 @@
   @Inject private RequestScopeOperations requestScopeOperations;
   @Inject private Sequences seq;
   @Inject private StalenessChecker stalenessChecker;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @After
   public void consistencyCheck() throws Exception {
@@ -1334,9 +1334,7 @@
     restartAsSlave();
 
     GroupIndexedCounter groupIndexedCounter = new GroupIndexedCounter();
-    RegistrationHandle groupIndexEventCounterHandle =
-        groupIndexedListeners.add("gerrit", groupIndexedCounter);
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(groupIndexedCounter)) {
       // Running the reindexer right after startup should not need to reindex any group since
       // reindexing was already done on startup.
       slaveGroupIndexer.run();
@@ -1372,8 +1370,6 @@
       }
       slaveGroupIndexer.run();
       groupIndexedCounter.assertReindexOf(groupUuid);
-    } finally {
-      groupIndexEventCounterHandle.remove();
     }
   }
 
@@ -1391,14 +1387,10 @@
     restartAsSlave();
 
     GroupIndexedCounter groupIndexedCounter = new GroupIndexedCounter();
-    RegistrationHandle groupIndexEventCounterHandle =
-        groupIndexedListeners.add("gerrit", groupIndexedCounter);
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(groupIndexedCounter)) {
       // No group indexing happened on startup. All groups should be reindexed now.
       slaveGroupIndexer.run();
       groupIndexedCounter.assertReindexOf(expectedGroups);
-    } finally {
-      groupIndexEventCounterHandle.remove();
     }
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
index 2087f939..47eec0d 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
@@ -40,6 +40,8 @@
 import com.google.common.collect.Iterators;
 import com.google.common.collect.ListMultimap;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.RestResponse;
 import com.google.gerrit.acceptance.TestAccount;
@@ -75,8 +77,6 @@
 import com.google.gerrit.extensions.common.RevisionInfo;
 import com.google.gerrit.extensions.common.WebLinkInfo;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
@@ -117,11 +117,10 @@
 import org.junit.Test;
 
 public class RevisionIT extends AbstractDaemonTest {
-  @Inject private DynamicSet<ChangeIndexedListener> changeIndexedListeners;
-  @Inject private DynamicSet<PatchSetWebLink> patchSetLinks;
   @Inject private GetRevisionActions getRevisionActions;
   @Inject private ProjectOperations projectOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Test
   public void reviewTriplet() throws Exception {
@@ -1079,25 +1078,22 @@
 
     // Using the API returns the correct value, and reindexes as well.
     CountDownLatch reindexed = new CountDownLatch(1);
-    RegistrationHandle handle =
-        changeIndexedListeners.add(
-            "gerrit",
-            new ChangeIndexedListener() {
-              @Override
-              public void onChangeIndexed(String projectName, int id) {
-                if (id == id2.get()) {
-                  reindexed.countDown();
-                }
-              }
+    ChangeIndexedListener listener =
+        new ChangeIndexedListener() {
+          @Override
+          public void onChangeIndexed(String projectName, int id) {
+            if (id == id2.get()) {
+              reindexed.countDown();
+            }
+          }
 
-              @Override
-              public void onChangeDeleted(int id) {}
-            });
-    try {
+          @Override
+          public void onChangeDeleted(int id) {}
+        };
+
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
       assertMergeable(r2.getChangeId(), true);
       reindexed.await();
-    } finally {
-      handle.remove();
     }
 
     List<ChangeInfo> changes = search.call();
@@ -1315,10 +1311,14 @@
   @Test
   public void commit() throws Exception {
     WebLinkInfo expectedWebLinkInfo = new WebLinkInfo("foo", "imageUrl", "url");
-    RegistrationHandle handle =
-        patchSetLinks.add("gerrit", (projectName, commit) -> expectedWebLinkInfo);
-
-    try {
+    PatchSetWebLink link =
+        new PatchSetWebLink() {
+          @Override
+          public WebLinkInfo getPatchSetWebLink(String projectName, String commit) {
+            return expectedWebLinkInfo;
+          }
+        };
+    try (Registration registration = extensionRegistry.newRegistration().add(link)) {
       PushOneCommit.Result r = createChange();
       RevCommit c = r.getCommit();
 
@@ -1340,8 +1340,6 @@
       assertThat(webLinkInfo.imageUrl).isEqualTo(expectedWebLinkInfo.imageUrl);
       assertThat(webLinkInfo.url).isEqualTo(expectedWebLinkInfo.url);
       assertThat(webLinkInfo.target).isEqualTo(expectedWebLinkInfo.target);
-    } finally {
-      handle.remove();
     }
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java b/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java
index e8ab515..8afa0e0 100644
--- a/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java
+++ b/javatests/com/google/gerrit/acceptance/git/AbstractPushForReview.java
@@ -50,6 +50,8 @@
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Streams;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.GitUtil;
 import com.google.gerrit.acceptance.PushOneCommit;
@@ -82,8 +84,6 @@
 import com.google.gerrit.extensions.common.EditInfo;
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.common.RevisionInfo;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.git.ObjectIds;
 import com.google.gerrit.mail.Address;
 import com.google.gerrit.reviewdb.client.AccountGroup;
@@ -150,12 +150,11 @@
 
   @Inject private ProjectOperations projectOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   private static String NEW_CHANGE_INDICATOR = " [NEW]";
   private LabelType patchSetLock;
 
-  @Inject private DynamicSet<CommitValidationListener> commitValidators;
-
   @Before
   public void setUpPatchSetLock() throws Exception {
     try (ProjectConfigUpdate u = updateProject(project)) {
@@ -2206,24 +2205,16 @@
   @GerritConfig(name = "receive.maxBatchCommits", value = "2")
   @Test
   public void maxBatchCommitsWithDefaultValidator() throws Exception {
-    TestValidator validator = new TestValidator();
-    RegistrationHandle handle = commitValidators.add("test-validator", validator);
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(new TestValidator())) {
       testMaxBatchCommits();
-    } finally {
-      handle.remove();
     }
   }
 
   @GerritConfig(name = "receive.maxBatchCommits", value = "2")
   @Test
   public void maxBatchCommitsWithValidateAllCommitsValidator() throws Exception {
-    TestValidator validator = new TestValidator(true);
-    RegistrationHandle handle = commitValidators.add("test-validator", validator);
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(new TestValidator())) {
       testMaxBatchCommits();
-    } finally {
-      handle.remove();
     }
   }
 
@@ -2281,10 +2272,7 @@
   public void skipValidation() throws Exception {
     String master = "refs/heads/master";
     TestValidator validator = new TestValidator();
-    RegistrationHandle handle = commitValidators.add("test-validator", validator);
-    RegistrationHandle handle2 = null;
-
-    try {
+    try (Registration registration = extensionRegistry.newRegistration().add(validator)) {
       // Validation listener is called on normal push
       PushOneCommit push =
           pushFactory.create(admin.newIdent(), testRepo, "change1", "a.txt", "content");
@@ -2313,20 +2301,16 @@
       // Validation listener that needs to validate all commits gets called even
       // when the skip option is used.
       TestValidator validator2 = new TestValidator(true);
-      handle2 = commitValidators.add("test-validator-2", validator2);
-      PushOneCommit push4 =
-          pushFactory.create(admin.newIdent(), testRepo, "change2", "b.txt", "content");
-      push4.setPushOptions(ImmutableList.of(PUSH_OPTION_SKIP_VALIDATION));
-      r = push4.to(master);
-      r.assertOkStatus();
-      // First listener was not called; its count remains the same.
-      assertThat(validator.count()).isEqualTo(1);
-      // Second listener was called.
-      assertThat(validator2.count()).isEqualTo(1);
-    } finally {
-      handle.remove();
-      if (handle2 != null) {
-        handle2.remove();
+      try (Registration registration2 = extensionRegistry.newRegistration().add(validator2)) {
+        PushOneCommit push4 =
+            pushFactory.create(admin.newIdent(), testRepo, "change2", "b.txt", "content");
+        push4.setPushOptions(ImmutableList.of(PUSH_OPTION_SKIP_VALIDATION));
+        r = push4.to(master);
+        r.assertOkStatus();
+        // First listener was not called; its count remains the same.
+        assertThat(validator.count()).isEqualTo(1);
+        // Second listener was called.
+        assertThat(validator2.count()).isEqualTo(1);
       }
     }
   }
diff --git a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
index f8176a5..f633842 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/AbstractReindexTests.java
@@ -74,13 +74,13 @@
           .containsExactly(changeId);
       // Query account index
       assertThat(gApi.accounts().query("admin").get().stream().map(a -> a._accountId))
-          .containsExactly(adminId.get());
+          .containsExactly(admin.id().get());
       // Query group index
       assertThat(
               gApi.groups().query("Group").withOption(MEMBERS).get().stream()
                   .flatMap(g -> g.members.stream())
                   .map(a -> a._accountId))
-          .containsExactly(adminId.get());
+          .containsExactly(admin.id().get());
       // Query project index
       assertThat(gApi.projects().query(project.get()).get().stream().map(p -> p.name))
           .containsExactly(project.get());
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
index c0083d2..154fabf 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AbstractSubmit.java
@@ -42,6 +42,8 @@
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.GitUtil;
 import com.google.gerrit.acceptance.NoHttpd;
@@ -67,8 +69,6 @@
 import com.google.gerrit.extensions.common.ChangeInput;
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
@@ -118,7 +118,6 @@
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.ReceiveCommand;
 import org.eclipse.jgit.transport.RefSpec;
-import org.junit.After;
 import org.junit.Test;
 
 @NoHttpd
@@ -131,21 +130,11 @@
   }
 
   @Inject private ApprovalsUtil approvalsUtil;
-  @Inject private DynamicSet<OnSubmitValidationListener> onSubmitValidationListeners;
-  @Inject private DynamicSet<ChangeIndexedListener> changeIndexedListeners;
   @Inject private IdentifiedUser.GenericFactory userFactory;
   @Inject private ProjectOperations projectOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
   @Inject private Submit submitHandler;
-
-  private RegistrationHandle onSubmitValidatorHandle;
-
-  @After
-  public void removeOnSubmitValidator() {
-    if (onSubmitValidatorHandle != null) {
-      onSubmitValidatorHandle.remove();
-    }
-  }
+  @Inject private ExtensionRegistry extensionRegistry;
 
   protected abstract SubmitType getSubmitType();
 
@@ -821,23 +810,28 @@
   @Test
   public void submitWithValidation() throws Throwable {
     AtomicBoolean called = new AtomicBoolean(false);
-    this.addOnSubmitValidationListener(
-        args -> {
-          called.set(true);
-          HashSet<String> refs = Sets.newHashSet(args.getCommands().keySet());
-          assertThat(refs).contains("refs/heads/master");
-          refs.remove("refs/heads/master");
-          if (!refs.isEmpty()) {
-            // Some submit strategies need to insert new patchset.
-            assertThat(refs).hasSize(1);
-            assertThat(refs.iterator().next()).startsWith(RefNames.REFS_CHANGES);
+    OnSubmitValidationListener listener =
+        new OnSubmitValidationListener() {
+          @Override
+          public void preBranchUpdate(Arguments args) throws ValidationException {
+            called.set(true);
+            HashSet<String> refs = Sets.newHashSet(args.getCommands().keySet());
+            assertThat(refs).contains("refs/heads/master");
+            refs.remove("refs/heads/master");
+            if (!refs.isEmpty()) {
+              // Some submit strategies need to insert new patchset.
+              assertThat(refs).hasSize(1);
+              assertThat(refs.iterator().next()).startsWith(RefNames.REFS_CHANGES);
+            }
           }
-        });
+        };
 
-    PushOneCommit.Result change = createChange();
-    approve(change.getChangeId());
-    submit(change.getChangeId());
-    assertThat(called.get()).isTrue();
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      PushOneCommit.Result change = createChange();
+      approve(change.getChangeId());
+      submit(change.getChangeId());
+      assertThat(called.get()).isTrue();
+    }
   }
 
   @Test
@@ -872,34 +866,39 @@
     // Since there are 2 repos, first submit attempt will fail, the second will
     // succeed.
     List<String> projectsCalled = new ArrayList<>(4);
-    this.addOnSubmitValidationListener(
-        args -> {
-          String master = "refs/heads/master";
-          assertThat(args.getCommands()).containsKey(master);
-          ReceiveCommand cmd = args.getCommands().get(master);
-          ObjectId newMasterId = cmd.getNewId();
-          try (Repository repo = repoManager.openRepository(args.getProject())) {
-            assertThat(repo.exactRef(master).getObjectId()).isEqualTo(cmd.getOldId());
-            assertThat(args.getRef(master)).hasValue(newMasterId);
-            args.getRevWalk().parseBody(args.getRevWalk().parseCommit(newMasterId));
-          } catch (IOException e) {
-            throw new AssertionError("failed checking new ref value", e);
+    OnSubmitValidationListener listener =
+        new OnSubmitValidationListener() {
+          @Override
+          public void preBranchUpdate(Arguments args) throws ValidationException {
+            String master = "refs/heads/master";
+            assertThat(args.getCommands()).containsKey(master);
+            ReceiveCommand cmd = args.getCommands().get(master);
+            ObjectId newMasterId = cmd.getNewId();
+            try (Repository repo = repoManager.openRepository(args.getProject())) {
+              assertThat(repo.exactRef(master).getObjectId()).isEqualTo(cmd.getOldId());
+              assertThat(args.getRef(master)).hasValue(newMasterId);
+              args.getRevWalk().parseBody(args.getRevWalk().parseCommit(newMasterId));
+            } catch (IOException e) {
+              throw new AssertionError("failed checking new ref value", e);
+            }
+            projectsCalled.add(args.getProject().get());
+            if (projectsCalled.size() == 2) {
+              throw new ValidationException("time to fail");
+            }
           }
-          projectsCalled.add(args.getProject().get());
-          if (projectsCalled.size() == 2) {
-            throw new ValidationException("time to fail");
-          }
-        });
-    submitWithConflict(change4.getChangeId(), "time to fail");
-    assertThat(projectsCalled).containsExactly(keyA.get(), keyB.get());
-    for (PushOneCommit.Result change : changes) {
-      change.assertChange(Change.Status.NEW, name(topic), admin);
-    }
+        };
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      submitWithConflict(change4.getChangeId(), "time to fail");
+      assertThat(projectsCalled).containsExactly(keyA.get(), keyB.get());
+      for (PushOneCommit.Result change : changes) {
+        change.assertChange(Change.Status.NEW, name(topic), admin);
+      }
 
-    submit(change4.getChangeId());
-    assertThat(projectsCalled).containsExactly(keyA.get(), keyB.get(), keyA.get(), keyB.get());
-    for (PushOneCommit.Result change : changes) {
-      change.assertChange(Change.Status.MERGED, name(topic), admin);
+      submit(change4.getChangeId());
+      assertThat(projectsCalled).containsExactly(keyA.get(), keyB.get(), keyA.get(), keyB.get());
+      for (PushOneCommit.Result change : changes) {
+        change.assertChange(Change.Status.MERGED, name(topic), admin);
+      }
     }
   }
 
@@ -1228,9 +1227,8 @@
     PushOneCommit.Result changeOtherBranch = createChange("refs/for/dev");
 
     ChangeIndexedListener changeIndexedListener = mock(ChangeIndexedListener.class);
-    RegistrationHandle registrationHandle =
-        changeIndexedListeners.add("gerrit", changeIndexedListener);
-    try {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedListener)) {
       // submit a change, this should trigger asynchronous reindexing of the open changes on the
       // same branch
       approve(change1.getChangeId());
@@ -1257,8 +1255,6 @@
       // open changes on other branches don't get reindexed
       verify(changeIndexedListener, times(0))
           .onChangeScheduledForIndexing(project.get(), changeOtherBranch.getChange().getId().get());
-    } finally {
-      registrationHandle.remove();
     }
   }
 
@@ -1438,11 +1434,6 @@
     return getRemoteLog(project, "master");
   }
 
-  protected void addOnSubmitValidationListener(OnSubmitValidationListener listener) {
-    assertThat(onSubmitValidatorHandle).isNull();
-    onSubmitValidatorHandle = onSubmitValidationListeners.add("gerrit", listener);
-  }
-
   private String getLatestDiff(Repository repo) throws Throwable {
     ObjectId oldTreeId = repo.resolve("HEAD~1^{tree}");
     ObjectId newTreeId = repo.resolve("HEAD^{tree}");
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/ActionsIT.java b/javatests/com/google/gerrit/acceptance/rest/change/ActionsIT.java
index aeb5a4b..f2b8468 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/ActionsIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/ActionsIT.java
@@ -38,6 +38,7 @@
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.server.change.RevisionJson;
+import com.google.gerrit.server.change.testing.TestChangeETagComputation;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.testing.ConfigSuite;
 import com.google.inject.Inject;
@@ -195,7 +196,8 @@
     String change = createChange().getChangeId();
     String oldETag = getETag(change);
 
-    try (Registration registration = extensionRegistry.newRegistration().add((p, id) -> "foo")) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(TestChangeETagComputation.withETag("foo"))) {
       assertThat(getETag(change)).isNotEqualTo(oldETag);
     }
 
@@ -207,7 +209,8 @@
     String change = createChange().getChangeId();
     String oldETag = getETag(change);
 
-    try (Registration registration = extensionRegistry.newRegistration().add((p, id) -> null)) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(TestChangeETagComputation.withETag(null))) {
       assertThat(getETag(change)).isEqualTo(oldETag);
     }
   }
@@ -221,9 +224,8 @@
         extensionRegistry
             .newRegistration()
             .add(
-                (p, id) -> {
-                  throw new StorageException("exception during test");
-                })) {
+                TestChangeETagComputation.withException(
+                    new StorageException("exception during test")))) {
       assertThat(getETag(change)).isEqualTo(oldETag);
     }
   }
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/SubmitByCherryPickIT.java b/javatests/com/google/gerrit/acceptance/rest/change/SubmitByCherryPickIT.java
index 16b7690..6f519f1 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/SubmitByCherryPickIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/SubmitByCherryPickIT.java
@@ -19,6 +19,8 @@
 import static com.google.gerrit.extensions.client.ListChangesOption.MESSAGES;
 
 import com.google.common.collect.Iterables;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.TestProjectInput;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -29,9 +31,6 @@
 import com.google.gerrit.extensions.client.ListChangesOption;
 import com.google.gerrit.extensions.client.SubmitType;
 import com.google.gerrit.extensions.common.ChangeInfo;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
-import com.google.gerrit.server.git.ChangeMessageModifier;
 import com.google.gerrit.server.submit.CommitMergeStatus;
 import com.google.inject.Inject;
 import java.util.List;
@@ -40,8 +39,8 @@
 import org.junit.Test;
 
 public class SubmitByCherryPickIT extends AbstractSubmit {
-  @Inject private DynamicSet<ChangeMessageModifier> changeMessageModifiers;
   @Inject private ProjectOperations projectOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Override
   protected SubmitType getSubmitType() {
@@ -89,15 +88,13 @@
   @Test
   public void changeMessageOnSubmit() throws Throwable {
     PushOneCommit.Result change = createChange();
-    RegistrationHandle handle =
-        changeMessageModifiers.add(
-            "gerrit",
-            (newCommitMessage, original, mergeTip, destination) ->
-                newCommitMessage + "Custom: " + destination.branch());
-    try {
+    try (Registration registration =
+        extensionRegistry
+            .newRegistration()
+            .add(
+                (newCommitMessage, original, mergeTip, destination) ->
+                    newCommitMessage + "Custom: " + destination.branch())) {
       submit(change.getChangeId());
-    } finally {
-      handle.remove();
     }
     testRepo.git().fetch().setRemote("origin").call();
     ChangeInfo info = get(change.getChangeId(), CURRENT_REVISION);
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/SubmitByRebaseAlwaysIT.java b/javatests/com/google/gerrit/acceptance/rest/change/SubmitByRebaseAlwaysIT.java
index 1808480..0cdc0e9 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/SubmitByRebaseAlwaysIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/SubmitByRebaseAlwaysIT.java
@@ -20,6 +20,8 @@
 
 import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableList;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.TestProjectInput;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -28,24 +30,20 @@
 import com.google.gerrit.extensions.client.SubmitType;
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.registration.DynamicItem;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.server.config.UrlFormatter;
 import com.google.gerrit.server.git.ChangeMessageModifier;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.inject.Inject;
-import java.util.ArrayDeque;
-import java.util.Deque;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.junit.Test;
 
 public class SubmitByRebaseAlwaysIT extends AbstractSubmitByRebase {
-  @Inject private DynamicSet<ChangeMessageModifier> changeMessageModifiers;
   @Inject private DynamicItem<UrlFormatter> urlFormatter;
   @Inject private ProjectOperations projectOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Override
   protected SubmitType getSubmitType() {
@@ -99,7 +97,8 @@
     ChangeMessageModifier modifier3 =
         (msg, orig, tip, dest) -> msg + "Dest: " + dest.shortName() + "\n";
 
-    try (AutoCloseable ignored = installChangeMessageModifiers(modifier1, modifier2, modifier3)) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(modifier1).add(modifier2).add(modifier3)) {
       ImmutableList<PushOneCommit.Result> changes = submitWithRebase(admin);
       ChangeData cd1 = changes.get(0).getChange();
       ChangeData cd2 = changes.get(1).getChange();
@@ -128,7 +127,8 @@
           throw new IllegalStateException("boom");
         };
     ChangeMessageModifier modifier2 = (msg, orig, tip, dest) -> msg + "A-footer: value\n";
-    try (AutoCloseable ignored = installChangeMessageModifiers(modifier1, modifier2)) {
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(modifier1).add(modifier2)) {
       ResourceConflictException thrown =
           assertThrows(ResourceConflictException.class, () -> submitWithRebase());
       Throwable cause = Throwables.getRootCause(thrown);
@@ -141,7 +141,11 @@
   public void changeMessageModifierReturningNullShortCircuits() throws Throwable {
     ChangeMessageModifier modifier1 = (msg, orig, tip, dest) -> null;
     ChangeMessageModifier modifier2 = (msg, orig, tip, dest) -> msg + "A-footer: value\n";
-    try (AutoCloseable ignored = installChangeMessageModifiers(modifier1, modifier2)) {
+    try (Registration registration =
+        extensionRegistry
+            .newRegistration()
+            .add(modifier1, "modifier-1")
+            .add(modifier2, "modifier-2")) {
       ResourceConflictException thrown =
           assertThrows(ResourceConflictException.class, () -> submitWithRebase());
       Throwable cause = Throwables.getRootCause(thrown);
@@ -155,18 +159,6 @@
     }
   }
 
-  private AutoCloseable installChangeMessageModifiers(ChangeMessageModifier... modifiers) {
-    Deque<RegistrationHandle> handles = new ArrayDeque<>(modifiers.length);
-    for (int i = 0; i < modifiers.length; i++) {
-      handles.push(changeMessageModifiers.add("modifier-" + (i + 1), modifiers[i]));
-    }
-    return () -> {
-      while (!handles.isEmpty()) {
-        handles.pop().remove();
-      }
-    };
-  }
-
   private void assertLatestRevisionHasFooters(PushOneCommit.Result change) throws Throwable {
     RevCommit c = getCurrentCommit(change);
     assertThat(c.getFooterLines(FooterConstants.CHANGE_ID)).isNotEmpty();
diff --git a/javatests/com/google/gerrit/acceptance/rest/config/IndexChangesIT.java b/javatests/com/google/gerrit/acceptance/rest/config/IndexChangesIT.java
index 7590532..a3c1722 100644
--- a/javatests/com/google/gerrit/acceptance/rest/config/IndexChangesIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/config/IndexChangesIT.java
@@ -21,87 +21,84 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.ChangeIndexedCounter;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.common.data.Permission;
 import com.google.gerrit.extensions.common.ChangeInfo;
-import com.google.gerrit.extensions.events.ChangeIndexedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.server.restapi.config.IndexChanges;
 import com.google.inject.Inject;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 public class IndexChangesIT extends AbstractDaemonTest {
 
-  @Inject private DynamicSet<ChangeIndexedListener> changeIndexedListeners;
   @Inject private ProjectOperations projectOperations;
-
-  private ChangeIndexedCounter changeIndexedCounter;
-  private RegistrationHandle changeIndexedCounterHandle;
-
-  @Before
-  public void addChangeIndexedCounter() {
-    changeIndexedCounter = new ChangeIndexedCounter();
-    changeIndexedCounterHandle = changeIndexedListeners.add("gerrit", changeIndexedCounter);
-  }
-
-  @After
-  public void removeChangeIndexedCounter() {
-    if (changeIndexedCounterHandle != null) {
-      changeIndexedCounterHandle.remove();
-    }
-  }
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Test
   public void indexRequestFromNonAdminRejected() throws Exception {
-    String changeId = createChange().getChangeId();
-    IndexChanges.Input in = new IndexChanges.Input();
-    in.changes = ImmutableSet.of(changeId);
-    changeIndexedCounter.clear();
-    userRestSession.post("/config/server/index.changes", in).assertForbidden();
-    assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(0);
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      String changeId = createChange().getChangeId();
+      IndexChanges.Input in = new IndexChanges.Input();
+      in.changes = ImmutableSet.of(changeId);
+      changeIndexedCounter.clear();
+      userRestSession.post("/config/server/index.changes", in).assertForbidden();
+      assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(0);
+    }
   }
 
   @Test
   public void indexVisibleChange() throws Exception {
-    String changeId = createChange().getChangeId();
-    IndexChanges.Input in = new IndexChanges.Input();
-    in.changes = ImmutableSet.of(changeId);
-    changeIndexedCounter.clear();
-    adminRestSession.post("/config/server/index.changes", in).assertOK();
-    assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(1);
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      String changeId = createChange().getChangeId();
+      IndexChanges.Input in = new IndexChanges.Input();
+      in.changes = ImmutableSet.of(changeId);
+      changeIndexedCounter.clear();
+      adminRestSession.post("/config/server/index.changes", in).assertOK();
+      assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(1);
+    }
   }
 
   @Test
   public void indexNonVisibleChange() throws Exception {
-    String changeId = createChange().getChangeId();
-    ChangeInfo changeInfo = info(changeId);
-    projectOperations
-        .project(project)
-        .forUpdate()
-        .add(block(Permission.READ).ref("refs/heads/master").group(REGISTERED_USERS))
-        .update();
-    IndexChanges.Input in = new IndexChanges.Input();
-    changeIndexedCounter.clear();
-    in.changes = ImmutableSet.of(changeId);
-    adminRestSession.post("/config/server/index.changes", in).assertOK();
-    assertThat(changeIndexedCounter.getCount(changeInfo)).isEqualTo(1);
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      String changeId = createChange().getChangeId();
+      ChangeInfo changeInfo = info(changeId);
+      projectOperations
+          .project(project)
+          .forUpdate()
+          .add(block(Permission.READ).ref("refs/heads/master").group(REGISTERED_USERS))
+          .update();
+      IndexChanges.Input in = new IndexChanges.Input();
+      changeIndexedCounter.clear();
+      in.changes = ImmutableSet.of(changeId);
+      adminRestSession.post("/config/server/index.changes", in).assertOK();
+      assertThat(changeIndexedCounter.getCount(changeInfo)).isEqualTo(1);
+    }
   }
 
   @Test
   public void indexMultipleChanges() throws Exception {
-    ImmutableSet.Builder<String> changeIds = ImmutableSet.builder();
-    for (int i = 0; i < 10; i++) {
-      changeIds.add(createChange().getChangeId());
-    }
-    IndexChanges.Input in = new IndexChanges.Input();
-    in.changes = changeIds.build();
-    changeIndexedCounter.clear();
-    adminRestSession.post("/config/server/index.changes", in).assertOK();
-    for (String changeId : in.changes) {
-      assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(1);
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      ImmutableSet.Builder<String> changeIds = ImmutableSet.builder();
+      for (int i = 0; i < 10; i++) {
+        changeIds.add(createChange().getChangeId());
+      }
+      IndexChanges.Input in = new IndexChanges.Input();
+      in.changes = changeIds.build();
+      changeIndexedCounter.clear();
+      adminRestSession.post("/config/server/index.changes", in).assertOK();
+      for (String changeId : in.changes) {
+        assertThat(changeIndexedCounter.getCount(info(changeId))).isEqualTo(1);
+      }
     }
   }
 }
diff --git a/javatests/com/google/gerrit/acceptance/rest/project/AccessIT.java b/javatests/com/google/gerrit/acceptance/rest/project/AccessIT.java
index bb043c2..c6c26c9 100644
--- a/javatests/com/google/gerrit/acceptance/rest/project/AccessIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/project/AccessIT.java
@@ -22,6 +22,8 @@
 import static com.google.gerrit.truth.ConfigSubject.assertThat;
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GitUtil;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -40,8 +42,6 @@
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.common.GroupInfo;
 import com.google.gerrit.extensions.common.WebLinkInfo;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
@@ -72,9 +72,9 @@
 
   private static final String LABEL_CODE_REVIEW = "Code-Review";
 
-  @Inject private DynamicSet<FileHistoryWebLink> fileHistoryWebLinkDynamicSet;
   @Inject private ProjectOperations projectOperations;
   @Inject private RequestScopeOperations requestScopeOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   private Project.NameKey newProjectName;
 
@@ -89,39 +89,39 @@
     assertThat(inheritedName).isEqualTo(AllProjectsNameProvider.DEFAULT);
   }
 
+  private Registration newFileHistoryWebLink() {
+    FileHistoryWebLink weblink =
+        new FileHistoryWebLink() {
+          @Override
+          public WebLinkInfo getFileHistoryWebLink(
+              String projectName, String revision, String fileName) {
+            return new WebLinkInfo(
+                "name", "imageURL", "http://view/" + projectName + "/" + fileName);
+          }
+        };
+    return extensionRegistry.newRegistration().add(weblink);
+  }
+
   @Test
   public void webLink() throws Exception {
-    RegistrationHandle handle =
-        fileHistoryWebLinkDynamicSet.add(
-            "gerrit",
-            (projectName, revision, fileName) ->
-                new WebLinkInfo("name", "imageURL", "http://view/" + projectName + "/" + fileName));
-    try {
+    try (Registration registration = newFileHistoryWebLink()) {
       ProjectAccessInfo info = pApi().access();
       assertThat(info.configWebLinks).hasSize(1);
       assertThat(info.configWebLinks.get(0).url)
           .isEqualTo("http://view/" + newProjectName + "/project.config");
-    } finally {
-      handle.remove();
     }
   }
 
   @Test
   public void webLinkNoRefsMetaConfig() throws Exception {
-    RegistrationHandle handle =
-        fileHistoryWebLinkDynamicSet.add(
-            "gerrit",
-            (projectName, revision, fileName) ->
-                new WebLinkInfo("name", "imageURL", "http://view/" + projectName + "/" + fileName));
-    try (Repository repo = repoManager.openRepository(newProjectName)) {
+    try (Repository repo = repoManager.openRepository(newProjectName);
+        Registration registration = newFileHistoryWebLink()) {
       RefUpdate u = repo.updateRef(RefNames.REFS_CONFIG);
       u.setForceUpdate(true);
       assertThat(u.delete()).isEqualTo(Result.FORCED);
 
       // This should not crash.
       pApi().access();
-    } finally {
-      handle.remove();
     }
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/server/event/CommentAddedEventIT.java b/javatests/com/google/gerrit/acceptance/server/event/CommentAddedEventIT.java
index 46fc689..8469fff 100644
--- a/javatests/com/google/gerrit/acceptance/server/event/CommentAddedEventIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/event/CommentAddedEventIT.java
@@ -22,6 +22,8 @@
 import static com.google.gerrit.server.project.testing.TestLabels.value;
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
@@ -31,18 +33,15 @@
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.common.LabelInfo;
 import com.google.gerrit.extensions.events.CommentAddedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.inject.Inject;
-import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
 @NoHttpd
 public class CommentAddedEventIT extends AbstractDaemonTest {
 
-  @Inject private DynamicSet<CommentAddedListener> source;
   @Inject private ProjectOperations projectOperations;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   private final LabelType label =
       label("CustomLabel", value(1, "Positive"), value(0, "No score"), value(-1, "Negative"));
@@ -50,9 +49,6 @@
   private final LabelType pLabel =
       label("CustomLabel2", value(1, "Positive"), value(0, "No score"));
 
-  private RegistrationHandle eventListenerRegistration;
-  private CommentAddedListener.Event lastCommentAddedEvent;
-
   @Before
   public void setUp() throws Exception {
     projectOperations
@@ -61,12 +57,6 @@
         .add(allowLabel(label.getName()).ref("refs/heads/*").group(ANONYMOUS_USERS).range(-1, 1))
         .add(allowLabel(pLabel.getName()).ref("refs/heads/*").group(ANONYMOUS_USERS).range(0, 1))
         .update();
-    eventListenerRegistration = source.add("gerrit", event -> lastCommentAddedEvent = event);
-  }
-
-  @After
-  public void cleanup() {
-    eventListenerRegistration.remove();
   }
 
   private void saveLabelConfig() throws Exception {
@@ -77,16 +67,30 @@
     }
   }
 
+  private static class TestListener implements CommentAddedListener {
+    private CommentAddedListener.Event lastCommentAddedEvent;
+
+    @Override
+    public void onCommentAdded(Event event) {
+      lastCommentAddedEvent = event;
+    }
+
+    public CommentAddedListener.Event getLastCommentAddedEvent() {
+      assertThat(lastCommentAddedEvent).isNotNull();
+      return lastCommentAddedEvent;
+    }
+  }
+
   /* Need to lookup info for the label under test since there can be multiple
    * labels defined.  By default Gerrit already has a Code-Review label.
    */
-  private ApprovalValues getApprovalValues(LabelType label) {
+  private ApprovalValues getApprovalValues(LabelType label, TestListener listener) {
     ApprovalValues res = new ApprovalValues();
-    ApprovalInfo info = lastCommentAddedEvent.getApprovals().get(label.getName());
+    ApprovalInfo info = listener.getLastCommentAddedEvent().getApprovals().get(label.getName());
     if (info != null) {
       res.value = info.value;
     }
-    info = lastCommentAddedEvent.getOldApprovals().get(label.getName());
+    info = listener.getLastCommentAddedEvent().getOldApprovals().get(label.getName());
     if (info != null) {
       res.oldValue = info.value;
     }
@@ -97,15 +101,18 @@
   public void newChangeWithVote() throws Exception {
     saveLabelConfig();
 
-    // push a new change with -1 vote
-    PushOneCommit.Result r = createChange();
-    ReviewInput reviewInput = new ReviewInput().label(label.getName(), (short) -1);
-    revision(r).review(reviewInput);
-    ApprovalValues attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(0);
-    assertThat(attr.value).isEqualTo(-1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
+    TestListener listener = new TestListener();
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      // push a new change with -1 vote
+      PushOneCommit.Result r = createChange();
+      ReviewInput reviewInput = new ReviewInput().label(label.getName(), (short) -1);
+      revision(r).review(reviewInput);
+      ApprovalValues attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(0);
+      assertThat(attr.value).isEqualTo(-1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
+    }
   }
 
   @Test
@@ -116,17 +123,19 @@
     PushOneCommit.Result r = createChange();
     ReviewInput reviewInput = new ReviewInput().message(label.getName());
     revision(r).review(reviewInput);
-
-    // push a new revision with +1 vote
-    ChangeInfo c = info(r.getChangeId());
-    r = amendChange(c.changeId);
-    reviewInput = new ReviewInput().label(label.getName(), (short) 1);
-    revision(r).review(reviewInput);
-    ApprovalValues attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(0);
-    assertThat(attr.value).isEqualTo(1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 2: %s+1", label.getName()));
+    TestListener listener = new TestListener();
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      // push a new revision with +1 vote
+      ChangeInfo c = info(r.getChangeId());
+      r = amendChange(c.changeId);
+      reviewInput = new ReviewInput().label(label.getName(), (short) 1);
+      revision(r).review(reviewInput);
+      ApprovalValues attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(0);
+      assertThat(attr.value).isEqualTo(1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 2: %s+1", label.getName()));
+    }
   }
 
   @Test
@@ -136,114 +145,120 @@
     // push a change
     PushOneCommit.Result r = createChange();
 
-    // review with message only, do not apply votes
-    ReviewInput reviewInput = new ReviewInput().message(label.getName());
-    revision(r).review(reviewInput);
-    // reply message only so vote is shown as 0
-    ApprovalValues attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isNull();
-    assertThat(attr.value).isEqualTo(0);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1:\n\n%s", label.getName()));
+    TestListener listener = new TestListener();
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      // review with message only, do not apply votes
+      ReviewInput reviewInput = new ReviewInput().message(label.getName());
+      revision(r).review(reviewInput);
+      // reply message only so vote is shown as 0
+      ApprovalValues attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isNull();
+      assertThat(attr.value).isEqualTo(0);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1:\n\n%s", label.getName()));
 
-    // transition from un-voted to -1 vote
-    reviewInput = new ReviewInput().label(label.getName(), -1);
-    revision(r).review(reviewInput);
-    attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(0);
-    assertThat(attr.value).isEqualTo(-1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
+      // transition from un-voted to -1 vote
+      reviewInput = new ReviewInput().label(label.getName(), -1);
+      revision(r).review(reviewInput);
+      attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(0);
+      assertThat(attr.value).isEqualTo(-1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
 
-    // transition vote from -1 to 0
-    reviewInput = new ReviewInput().label(label.getName(), 0);
-    revision(r).review(reviewInput);
-    attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(-1);
-    assertThat(attr.value).isEqualTo(0);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: -%s", label.getName()));
+      // transition vote from -1 to 0
+      reviewInput = new ReviewInput().label(label.getName(), 0);
+      revision(r).review(reviewInput);
+      attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(-1);
+      assertThat(attr.value).isEqualTo(0);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: -%s", label.getName()));
 
-    // transition vote from 0 to 1
-    reviewInput = new ReviewInput().label(label.getName(), 1);
-    revision(r).review(reviewInput);
-    attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(0);
-    assertThat(attr.value).isEqualTo(1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s+1", label.getName()));
+      // transition vote from 0 to 1
+      reviewInput = new ReviewInput().label(label.getName(), 1);
+      revision(r).review(reviewInput);
+      attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(0);
+      assertThat(attr.value).isEqualTo(1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s+1", label.getName()));
 
-    // transition vote from 1 to -1
-    reviewInput = new ReviewInput().label(label.getName(), -1);
-    revision(r).review(reviewInput);
-    attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isEqualTo(1);
-    assertThat(attr.value).isEqualTo(-1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
+      // transition vote from 1 to -1
+      reviewInput = new ReviewInput().label(label.getName(), -1);
+      revision(r).review(reviewInput);
+      attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isEqualTo(1);
+      assertThat(attr.value).isEqualTo(-1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s-1", label.getName()));
 
-    // review with message only, do not apply votes
-    reviewInput = new ReviewInput().message(label.getName());
-    revision(r).review(reviewInput);
-    attr = getApprovalValues(label);
-    assertThat(attr.oldValue).isNull(); // no vote change so not included
-    assertThat(attr.value).isEqualTo(-1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1:\n\n%s", label.getName()));
+      // review with message only, do not apply votes
+      reviewInput = new ReviewInput().message(label.getName());
+      revision(r).review(reviewInput);
+      attr = getApprovalValues(label, listener);
+      assertThat(attr.oldValue).isNull(); // no vote change so not included
+      assertThat(attr.value).isEqualTo(-1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1:\n\n%s", label.getName()));
+    }
   }
 
   @Test
   public void reviewChange_MultipleVotes() throws Exception {
-    saveLabelConfig();
-    PushOneCommit.Result r = createChange();
-    ReviewInput reviewInput = new ReviewInput().label(label.getName(), -1);
-    reviewInput.message = label.getName();
-    revision(r).review(reviewInput);
+    TestListener listener = new TestListener();
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      saveLabelConfig();
+      PushOneCommit.Result r = createChange();
+      ReviewInput reviewInput = new ReviewInput().label(label.getName(), -1);
+      reviewInput.message = label.getName();
+      revision(r).review(reviewInput);
 
-    ChangeInfo c = get(r.getChangeId(), DETAILED_LABELS);
-    LabelInfo q = c.labels.get(label.getName());
-    assertThat(q.all).hasSize(1);
-    ApprovalValues labelAttr = getApprovalValues(label);
-    assertThat(labelAttr.oldValue).isEqualTo(0);
-    assertThat(labelAttr.value).isEqualTo(-1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s-1\n\n%s", label.getName(), label.getName()));
+      ChangeInfo c = get(r.getChangeId(), DETAILED_LABELS);
+      LabelInfo q = c.labels.get(label.getName());
+      assertThat(q.all).hasSize(1);
+      ApprovalValues labelAttr = getApprovalValues(label, listener);
+      assertThat(labelAttr.oldValue).isEqualTo(0);
+      assertThat(labelAttr.value).isEqualTo(-1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s-1\n\n%s", label.getName(), label.getName()));
 
-    // there should be 3 approval labels (label, pLabel, and CRVV)
-    assertThat(lastCommentAddedEvent.getApprovals()).hasSize(3);
+      // there should be 3 approval labels (label, pLabel, and CRVV)
+      assertThat(listener.getLastCommentAddedEvent().getApprovals()).hasSize(3);
 
-    // check the approvals that were not voted on
-    ApprovalValues pLabelAttr = getApprovalValues(pLabel);
-    assertThat(pLabelAttr.oldValue).isNull();
-    assertThat(pLabelAttr.value).isEqualTo(0);
+      // check the approvals that were not voted on
+      ApprovalValues pLabelAttr = getApprovalValues(pLabel, listener);
+      assertThat(pLabelAttr.oldValue).isNull();
+      assertThat(pLabelAttr.value).isEqualTo(0);
 
-    LabelType crLabel = LabelType.withDefaultValues("Code-Review");
-    ApprovalValues crlAttr = getApprovalValues(crLabel);
-    assertThat(crlAttr.oldValue).isNull();
-    assertThat(crlAttr.value).isEqualTo(0);
+      LabelType crLabel = LabelType.withDefaultValues("Code-Review");
+      ApprovalValues crlAttr = getApprovalValues(crLabel, listener);
+      assertThat(crlAttr.oldValue).isNull();
+      assertThat(crlAttr.value).isEqualTo(0);
 
-    // update pLabel approval
-    reviewInput = new ReviewInput().label(pLabel.getName(), 1);
-    reviewInput.message = pLabel.getName();
-    revision(r).review(reviewInput);
+      // update pLabel approval
+      reviewInput = new ReviewInput().label(pLabel.getName(), 1);
+      reviewInput.message = pLabel.getName();
+      revision(r).review(reviewInput);
 
-    c = get(r.getChangeId(), DETAILED_LABELS);
-    q = c.labels.get(label.getName());
-    assertThat(q.all).hasSize(1);
-    pLabelAttr = getApprovalValues(pLabel);
-    assertThat(pLabelAttr.oldValue).isEqualTo(0);
-    assertThat(pLabelAttr.value).isEqualTo(1);
-    assertThat(lastCommentAddedEvent.getComment())
-        .isEqualTo(String.format("Patch Set 1: %s+1\n\n%s", pLabel.getName(), pLabel.getName()));
+      c = get(r.getChangeId(), DETAILED_LABELS);
+      q = c.labels.get(label.getName());
+      assertThat(q.all).hasSize(1);
+      pLabelAttr = getApprovalValues(pLabel, listener);
+      assertThat(pLabelAttr.oldValue).isEqualTo(0);
+      assertThat(pLabelAttr.value).isEqualTo(1);
+      assertThat(listener.getLastCommentAddedEvent().getComment())
+          .isEqualTo(String.format("Patch Set 1: %s+1\n\n%s", pLabel.getName(), pLabel.getName()));
 
-    // check the approvals that were not voted on
-    labelAttr = getApprovalValues(label);
-    assertThat(labelAttr.oldValue).isNull();
-    assertThat(labelAttr.value).isEqualTo(-1);
+      // check the approvals that were not voted on
+      labelAttr = getApprovalValues(label, listener);
+      assertThat(labelAttr.oldValue).isNull();
+      assertThat(labelAttr.value).isEqualTo(-1);
 
-    crlAttr = getApprovalValues(crLabel);
-    assertThat(crlAttr.oldValue).isNull();
-    assertThat(crlAttr.value).isEqualTo(0);
+      crlAttr = getApprovalValues(crLabel, listener);
+      assertThat(crlAttr.oldValue).isNull();
+      assertThat(crlAttr.value).isEqualTo(0);
+    }
   }
 
   private static class ApprovalValues {
diff --git a/javatests/com/google/gerrit/acceptance/server/event/EventPayloadIT.java b/javatests/com/google/gerrit/acceptance/server/event/EventPayloadIT.java
index 5ff1c32..8744cfad 100644
--- a/javatests/com/google/gerrit/acceptance/server/event/EventPayloadIT.java
+++ b/javatests/com/google/gerrit/acceptance/server/event/EventPayloadIT.java
@@ -17,49 +17,48 @@
 import static com.google.common.truth.Truth.assertThat;
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.extensions.events.RevisionCreatedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.inject.Inject;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 @NoHttpd
 public class EventPayloadIT extends AbstractDaemonTest {
-  @Inject private DynamicSet<RevisionCreatedListener> revisionCreatedListeners;
-
-  private RegistrationHandle eventListenerRegistration;
-  private RevisionCreatedListener.Event lastEvent;
-
-  @Before
-  public void setUp() throws Exception {
-    eventListenerRegistration = revisionCreatedListeners.add("gerrit", event -> lastEvent = event);
-  }
-
-  @After
-  public void cleanup() {
-    eventListenerRegistration.remove();
-  }
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Test
   public void defaultOptions() throws Exception {
-    createChange();
-
-    assertThat(lastEvent.getChange().submittable).isNotNull();
-    assertThat(lastEvent.getRevision().files).isNotEmpty();
+    RevisionCreatedListener listener =
+        new RevisionCreatedListener() {
+          @Override
+          public void onRevisionCreated(Event event) {
+            assertThat(event.getChange().submittable).isNotNull();
+            assertThat(event.getRevision().files).isNotEmpty();
+          }
+        };
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      createChange();
+    }
   }
 
   @Test
   @GerritConfig(name = "event.payload.listChangeOptions", value = "SKIP_MERGEABLE")
   public void configuredOptions() throws Exception {
-    createChange();
-
-    assertThat(lastEvent.getChange().submittable).isNull();
-    assertThat(lastEvent.getChange().mergeable).isNull();
-    assertThat(lastEvent.getRevision().files).isNull();
-    assertThat(lastEvent.getChange().subject).isNotEmpty();
+    RevisionCreatedListener listener =
+        new RevisionCreatedListener() {
+          @Override
+          public void onRevisionCreated(Event event) {
+            assertThat(event.getChange().submittable).isNull();
+            assertThat(event.getChange().mergeable).isNull();
+            assertThat(event.getRevision().files).isNull();
+            assertThat(event.getChange().subject).isNotEmpty();
+          }
+        };
+    try (Registration registration = extensionRegistry.newRegistration().add(listener)) {
+      createChange();
+    }
   }
 }
diff --git a/javatests/com/google/gerrit/acceptance/ssh/AbstractIndexTests.java b/javatests/com/google/gerrit/acceptance/ssh/AbstractIndexTests.java
index a03d7f3..c841559 100644
--- a/javatests/com/google/gerrit/acceptance/ssh/AbstractIndexTests.java
+++ b/javatests/com/google/gerrit/acceptance/ssh/AbstractIndexTests.java
@@ -20,102 +20,91 @@
 import com.google.common.base.Joiner;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.ChangeIndexedCounter;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.GerritConfig;
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.PushOneCommit;
 import com.google.gerrit.acceptance.UseSsh;
 import com.google.gerrit.extensions.common.ChangeInfo;
-import com.google.gerrit.extensions.events.ChangeIndexedListener;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.inject.Inject;
 import com.google.inject.Injector;
 import java.util.List;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 @NoHttpd
 @UseSsh
 public abstract class AbstractIndexTests extends AbstractDaemonTest {
-  @Inject private DynamicSet<ChangeIndexedListener> changeIndexedListeners;
-
-  private ChangeIndexedCounter changeIndexedCounter;
-  private RegistrationHandle changeIndexedCounterHandle;
+  @Inject private ExtensionRegistry extensionRegistry;
 
   /** @param injector injector */
   public void configureIndex(Injector injector) {}
 
-  @Before
-  public void addChangeIndexedCounter() {
-    changeIndexedCounter = new ChangeIndexedCounter();
-    changeIndexedCounterHandle = changeIndexedListeners.add("gerrit", changeIndexedCounter);
-  }
-
-  @After
-  public void removeChangeIndexedCounter() {
-    if (changeIndexedCounterHandle != null) {
-      changeIndexedCounterHandle.remove();
-    }
-  }
-
   @Test
   @GerritConfig(name = "index.autoReindexIfStale", value = "false")
   public void indexChange() throws Exception {
-    configureIndex(server.getTestInjector());
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      configureIndex(server.getTestInjector());
 
-    PushOneCommit.Result change = createChange("first change", "test1.txt", "test1");
-    String changeId = change.getChangeId();
-    String changeLegacyId = change.getChange().getId().toString();
-    ChangeInfo changeInfo = gApi.changes().id(changeId).get();
+      PushOneCommit.Result change = createChange("first change", "test1.txt", "test1");
+      String changeId = change.getChangeId();
+      String changeLegacyId = change.getChange().getId().toString();
+      ChangeInfo changeInfo = gApi.changes().id(changeId).get();
 
-    disableChangeIndexWrites();
-    amendChange(changeId, "second test", "test2.txt", "test2");
+      disableChangeIndexWrites();
+      amendChange(changeId, "second test", "test2.txt", "test2");
 
-    assertChangeQuery("message:second", change.getChange(), false);
-    enableChangeIndexWrites();
+      assertChangeQuery("message:second", change.getChange(), false);
+      enableChangeIndexWrites();
 
-    changeIndexedCounter.clear();
-    String cmd = Joiner.on(" ").join("gerrit", "index", "changes", changeLegacyId);
-    adminSshSession.exec(cmd);
-    adminSshSession.assertSuccess();
+      changeIndexedCounter.clear();
+      String cmd = Joiner.on(" ").join("gerrit", "index", "changes", changeLegacyId);
+      adminSshSession.exec(cmd);
+      adminSshSession.assertSuccess();
 
-    changeIndexedCounter.assertReindexOf(changeInfo, 1);
+      changeIndexedCounter.assertReindexOf(changeInfo, 1);
 
-    assertChangeQuery("message:second", change.getChange(), true);
+      assertChangeQuery("message:second", change.getChange(), true);
+    }
   }
 
   @Test
   @GerritConfig(name = "index.autoReindexIfStale", value = "false")
   public void indexProject() throws Exception {
-    configureIndex(server.getTestInjector());
+    ChangeIndexedCounter changeIndexedCounter = new ChangeIndexedCounter();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(changeIndexedCounter)) {
+      configureIndex(server.getTestInjector());
 
-    PushOneCommit.Result change = createChange("first change", "test1.txt", "test1");
-    String changeId = change.getChangeId();
-    ChangeInfo changeInfo = gApi.changes().id(changeId).get();
+      PushOneCommit.Result change = createChange("first change", "test1.txt", "test1");
+      String changeId = change.getChangeId();
+      ChangeInfo changeInfo = gApi.changes().id(changeId).get();
 
-    disableChangeIndexWrites();
-    amendChange(changeId, "second test", "test2.txt", "test2");
+      disableChangeIndexWrites();
+      amendChange(changeId, "second test", "test2.txt", "test2");
 
-    assertChangeQuery("message:second", change.getChange(), false);
-    enableChangeIndexWrites();
+      assertChangeQuery("message:second", change.getChange(), false);
+      enableChangeIndexWrites();
 
-    changeIndexedCounter.clear();
-    String cmd = Joiner.on(" ").join("gerrit", "index", "changes-in-project", project.get());
-    adminSshSession.exec(cmd);
-    adminSshSession.assertSuccess();
-
-    boolean indexing = true;
-    while (indexing) {
-      String out = adminSshSession.exec("gerrit show-queue --wide");
+      changeIndexedCounter.clear();
+      String cmd = Joiner.on(" ").join("gerrit", "index", "changes-in-project", project.get());
+      adminSshSession.exec(cmd);
       adminSshSession.assertSuccess();
-      indexing = out.contains("Index all changes of project " + project.get());
+
+      boolean indexing = true;
+      while (indexing) {
+        String out = adminSshSession.exec("gerrit show-queue --wide");
+        adminSshSession.assertSuccess();
+        indexing = out.contains("Index all changes of project " + project.get());
+      }
+
+      changeIndexedCounter.assertReindexOf(changeInfo, 1);
+
+      assertChangeQuery("message:second", change.getChange(), true);
     }
-
-    changeIndexedCounter.assertReindexOf(changeInfo, 1);
-
-    assertChangeQuery("message:second", change.getChange(), true);
   }
 
   protected void assertChangeQuery(String q, ChangeData change, boolean assertTrue)
diff --git a/javatests/com/google/gerrit/acceptance/ssh/SshTraceIT.java b/javatests/com/google/gerrit/acceptance/ssh/SshTraceIT.java
index 09e97b2..ae45d90 100644
--- a/javatests/com/google/gerrit/acceptance/ssh/SshTraceIT.java
+++ b/javatests/com/google/gerrit/acceptance/ssh/SshTraceIT.java
@@ -20,9 +20,9 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.ExtensionRegistry;
+import com.google.gerrit.acceptance.ExtensionRegistry.Registration;
 import com.google.gerrit.acceptance.UseSsh;
-import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.server.logging.LoggingContext;
 import com.google.gerrit.server.logging.Metadata;
 import com.google.gerrit.server.logging.PerformanceLogger;
@@ -33,66 +33,58 @@
 import com.google.inject.Inject;
 import java.util.ArrayList;
 import java.util.List;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 @UseSsh
 public class SshTraceIT extends AbstractDaemonTest {
-  @Inject private DynamicSet<ProjectCreationValidationListener> projectCreationValidationListeners;
-  @Inject private DynamicSet<PerformanceLogger> performanceLoggers;
-
-  private TraceValidatingProjectCreationValidationListener projectCreationListener;
-  private RegistrationHandle projectCreationListenerRegistrationHandle;
-  private TestPerformanceLogger testPerformanceLogger;
-  private RegistrationHandle performanceLoggerRegistrationHandle;
-
-  @Before
-  public void setup() {
-    projectCreationListener = new TraceValidatingProjectCreationValidationListener();
-    projectCreationListenerRegistrationHandle =
-        projectCreationValidationListeners.add("gerrit", projectCreationListener);
-    testPerformanceLogger = new TestPerformanceLogger();
-    performanceLoggerRegistrationHandle = performanceLoggers.add("gerrit", testPerformanceLogger);
-  }
-
-  @After
-  public void cleanup() {
-    projectCreationListenerRegistrationHandle.remove();
-    performanceLoggerRegistrationHandle.remove();
-  }
+  @Inject private ExtensionRegistry extensionRegistry;
 
   @Test
   public void sshCallWithoutTrace() throws Exception {
-    adminSshSession.exec("gerrit create-project new1");
-    adminSshSession.assertSuccess();
-    assertThat(projectCreationListener.traceId).isNull();
-    assertThat(projectCreationListener.foundTraceId).isFalse();
-    assertThat(projectCreationListener.isLoggingForced).isFalse();
+    TraceValidatingProjectCreationValidationListener projectCreationListener =
+        new TraceValidatingProjectCreationValidationListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(projectCreationListener)) {
+      adminSshSession.exec("gerrit create-project new1");
+      adminSshSession.assertSuccess();
+      assertThat(projectCreationListener.traceId).isNull();
+      assertThat(projectCreationListener.foundTraceId).isFalse();
+      assertThat(projectCreationListener.isLoggingForced).isFalse();
+    }
   }
 
   @Test
   public void sshCallWithTrace() throws Exception {
-    adminSshSession.exec("gerrit create-project --trace new2");
+    TraceValidatingProjectCreationValidationListener projectCreationListener =
+        new TraceValidatingProjectCreationValidationListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(projectCreationListener)) {
+      adminSshSession.exec("gerrit create-project --trace new2");
 
-    // The trace ID is written to stderr.
-    adminSshSession.assertFailure(RequestId.Type.TRACE_ID.name());
+      // The trace ID is written to stderr.
+      adminSshSession.assertFailure(RequestId.Type.TRACE_ID.name());
 
-    assertThat(projectCreationListener.traceId).isNotNull();
-    assertThat(projectCreationListener.foundTraceId).isTrue();
-    assertThat(projectCreationListener.isLoggingForced).isTrue();
+      assertThat(projectCreationListener.traceId).isNotNull();
+      assertThat(projectCreationListener.foundTraceId).isTrue();
+      assertThat(projectCreationListener.isLoggingForced).isTrue();
+    }
   }
 
   @Test
   public void sshCallWithTraceAndProvidedTraceId() throws Exception {
-    adminSshSession.exec("gerrit create-project --trace --trace-id issue/123 new3");
+    TraceValidatingProjectCreationValidationListener projectCreationListener =
+        new TraceValidatingProjectCreationValidationListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(projectCreationListener)) {
+      adminSshSession.exec("gerrit create-project --trace --trace-id issue/123 new3");
 
-    // The trace ID is written to stderr.
-    adminSshSession.assertFailure(RequestId.Type.TRACE_ID.name());
+      // The trace ID is written to stderr.
+      adminSshSession.assertFailure(RequestId.Type.TRACE_ID.name());
 
-    assertThat(projectCreationListener.traceId).isEqualTo("issue/123");
-    assertThat(projectCreationListener.foundTraceId).isTrue();
-    assertThat(projectCreationListener.isLoggingForced).isTrue();
+      assertThat(projectCreationListener.traceId).isEqualTo("issue/123");
+      assertThat(projectCreationListener.foundTraceId).isTrue();
+      assertThat(projectCreationListener.isLoggingForced).isTrue();
+    }
   }
 
   @Test
@@ -103,9 +95,13 @@
 
   @Test
   public void performanceLoggingForSshCall() throws Exception {
-    adminSshSession.exec("gerrit create-project new5");
-    adminSshSession.assertSuccess();
-    assertThat(testPerformanceLogger.logEntries()).isNotEmpty();
+    TestPerformanceLogger testPerformanceLogger = new TestPerformanceLogger();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(testPerformanceLogger)) {
+      adminSshSession.exec("gerrit create-project new5");
+      adminSshSession.assertSuccess();
+      assertThat(testPerformanceLogger.logEntries()).isNotEmpty();
+    }
   }
 
   private static class TraceValidatingProjectCreationValidationListener
diff --git a/javatests/com/google/gerrit/integration/git/BUILD b/javatests/com/google/gerrit/integration/git/BUILD
new file mode 100644
index 0000000..6a6f5ad
--- /dev/null
+++ b/javatests/com/google/gerrit/integration/git/BUILD
@@ -0,0 +1,7 @@
+load("//javatests/com/google/gerrit/acceptance:tests.bzl", "acceptance_tests")
+
+acceptance_tests(
+    srcs = glob(["*IT.java"]),
+    group = "git",
+    labels = ["git"],
+)
diff --git a/javatests/com/google/gerrit/integration/git/GitProtocolV2IT.java b/javatests/com/google/gerrit/integration/git/GitProtocolV2IT.java
new file mode 100644
index 0000000..ece4d4a
--- /dev/null
+++ b/javatests/com/google/gerrit/integration/git/GitProtocolV2IT.java
@@ -0,0 +1,236 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.integration.git;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.TruthJUnit.assume;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.allow;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.deny;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.gerrit.acceptance.AccountCreator;
+import com.google.gerrit.acceptance.GerritServer.TestSshServerAddress;
+import com.google.gerrit.acceptance.GitClientVersion;
+import com.google.gerrit.acceptance.StandaloneSiteTest;
+import com.google.gerrit.acceptance.TestAccount;
+import com.google.gerrit.acceptance.UseSsh;
+import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
+import com.google.gerrit.common.data.Permission;
+import com.google.gerrit.extensions.api.GerritApi;
+import com.google.gerrit.extensions.common.ChangeInput;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.group.SystemGroupBackend;
+import com.google.inject.Inject;
+import java.io.File;
+import java.net.InetSocketAddress;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Constants;
+import org.junit.Test;
+
+@UseSsh
+public class GitProtocolV2IT extends StandaloneSiteTest {
+  private final String[] SSH_KEYGEN_CMD =
+      new String[] {"ssh-keygen", "-t", "rsa", "-q", "-P", "", "-f"};
+  private final String[] GIT_LS_REMOTE =
+      new String[] {"git", "-c", "protocol.version=2", "ls-remote", "-o", "trace=12345"};
+  private final String GIT_SSH_COMMAND =
+      "ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -i";
+
+  @Inject private GerritApi gApi;
+  @Inject private AccountCreator accountCreator;
+  @Inject private ProjectOperations projectOperations;
+  @Inject private @TestSshServerAddress InetSocketAddress sshAddress;
+  @Inject private @GerritServerConfig Config config;
+
+  @Test
+  public void testGitWireProtocolV2WithSsh() throws Exception {
+    // Minimum required git-core version that supports wire protocol v2 is 2.18.0
+    GitClientVersion requiredGitVersion = new GitClientVersion(2, 18, 0);
+    GitClientVersion actualGitVersion =
+        new GitClientVersion(execute(ImmutableList.of("git", "version")));
+    // If not found, test succeeds with assumption violation
+    assume().that(actualGitVersion).isAtLeast(requiredGitVersion);
+
+    try (ServerContext ctx = startServer()) {
+      ctx.getInjector().injectMembers(this);
+
+      // Create project
+      Project.NameKey project = Project.nameKey("foo");
+      gApi.projects().create(project.get());
+
+      // Set up project permission
+      projectOperations
+          .project(project)
+          .forUpdate()
+          .add(deny(Permission.READ).ref("refs/*").group(SystemGroupBackend.ANONYMOUS_USERS))
+          .add(
+              allow(Permission.READ)
+                  .ref("refs/heads/master")
+                  .group(SystemGroupBackend.REGISTERED_USERS))
+          .update();
+
+      // Set protocol.version=2 in target repository
+      execute(
+          ImmutableList.of("git", "config", "protocol.version", "2"),
+          sitePaths.site_path.resolve("git").resolve(project.get() + Constants.DOT_GIT).toFile());
+
+      // Retrieve HTTP url
+      String url = config.getString("gerrit", null, "canonicalweburl");
+      String urlDestinationTemplate =
+          url.substring(0, 7)
+              + "%s:secret@"
+              + url.substring(7, url.length())
+              + "/a/"
+              + project.get();
+
+      // Retrieve SSH host and port
+      String sshDestinationTemplate =
+          "ssh://%s@" + sshAddress.getHostName() + ":" + sshAddress.getPort() + "/" + project.get();
+
+      // Admin user was already created by the base class
+      setUpUserAuthentication(admin.username());
+
+      // Create non-admin user
+      TestAccount user = accountCreator.user();
+      setUpUserAuthentication(user.username());
+
+      // Prepare data for new change on master branch
+      ChangeInput in = new ChangeInput(project.get(), "master", "Test public change");
+      in.newBranch = true;
+
+      // Create new change and retrieve SHA1 for the created patch set
+      String commit =
+          gApi.changes()
+              .id(gApi.changes().create(in).info().changeId)
+              .current()
+              .commit(false)
+              .commit;
+
+      // Prepare new change on secret branch
+      in = new ChangeInput(project.get(), "secret", "Test secret change");
+      in.newBranch = true;
+
+      // Create new change and retrieve SHA1 for the created patch set
+      String secretCommit =
+          gApi.changes()
+              .id(gApi.changes().create(in).info().changeId)
+              .current()
+              .commit(false)
+              .commit;
+
+      // Read refs from target repository using git wire protocol v2 over HTTP for admin user
+      String out =
+          execute(
+              ImmutableList.<String>builder()
+                  .add(GIT_LS_REMOTE)
+                  .add(String.format(urlDestinationTemplate, admin.username()))
+                  .build(),
+              ImmutableMap.of("GIT_TRACE_PACKET", "1"));
+
+      assertGitProtocolV2Refs(commit, out);
+      assertThat(out).contains(secretCommit);
+
+      // Read refs from target repository using git wire protocol v2 over SSH for admin user
+      out =
+          execute(
+              ImmutableList.<String>builder()
+                  .add(GIT_LS_REMOTE)
+                  .add(String.format(sshDestinationTemplate, admin.username()))
+                  .build(),
+              ImmutableMap.of(
+                  "GIT_SSH_COMMAND",
+                  GIT_SSH_COMMAND
+                      + sitePaths.data_dir.resolve(String.format("id_rsa_%s", admin.username())),
+                  "GIT_TRACE_PACKET",
+                  "1"));
+
+      assertGitProtocolV2Refs(commit, out);
+      assertThat(out).contains(secretCommit);
+
+      // Read refs from target repository using git wire protocol v2 over HTTP for non-admin user
+      out =
+          execute(
+              ImmutableList.<String>builder()
+                  .add(GIT_LS_REMOTE)
+                  .add(String.format(urlDestinationTemplate, user.username()))
+                  .build(),
+              ImmutableMap.of("GIT_TRACE_PACKET", "1"));
+
+      assertGitProtocolV2Refs(commit, out);
+      assertThat(out).doesNotContain(secretCommit);
+
+      // Read refs from target repository using git wire protocol v2 over SSH for non-admin user
+      out =
+          execute(
+              ImmutableList.<String>builder()
+                  .add(GIT_LS_REMOTE)
+                  .add(String.format(sshDestinationTemplate, user.username()))
+                  .build(),
+              ImmutableMap.of(
+                  "GIT_SSH_COMMAND",
+                  GIT_SSH_COMMAND
+                      + sitePaths.data_dir.resolve(String.format("id_rsa_%s", user.username())),
+                  "GIT_TRACE_PACKET",
+                  "1"));
+
+      assertGitProtocolV2Refs(commit, out);
+      assertThat(out).doesNotContain(secretCommit);
+    }
+  }
+
+  private void setUpUserAuthentication(String username) throws Exception {
+    // Assign HTTP password to user
+    gApi.accounts().id(username).setHttpPassword("secret");
+
+    // Generate private/public key for user
+    execute(
+        ImmutableList.<String>builder()
+            .add(SSH_KEYGEN_CMD)
+            .add(String.format("id_rsa_%s", username))
+            .build());
+
+    // Read the content of generated public key and add it for the user in Gerrit
+    gApi.accounts()
+        .id(username)
+        .addSshKey(
+            new String(
+                java.nio.file.Files.readAllBytes(
+                    sitePaths.data_dir.resolve(String.format("id_rsa_%s.pub", username))),
+                UTF_8));
+  }
+
+  private static void assertGitProtocolV2Refs(String commit, String out) {
+    assertThat(out).contains("git< version 2");
+    assertThat(out).contains("refs/changes/01/1/1");
+    assertThat(out).contains("refs/changes/01/1/meta");
+    assertThat(out).contains(commit);
+  }
+
+  private String execute(ImmutableList<String> cmd) throws Exception {
+    return execute(cmd, sitePaths.data_dir.toFile(), ImmutableMap.of());
+  }
+
+  private String execute(ImmutableList<String> cmd, ImmutableMap<String, String> env)
+      throws Exception {
+    return execute(cmd, sitePaths.data_dir.toFile(), env);
+  }
+
+  private static String execute(ImmutableList<String> cmd, File dir) throws Exception {
+    return execute(cmd, dir, ImmutableMap.of());
+  }
+}
diff --git a/javatests/com/google/gerrit/server/logging/MetadataTest.java b/javatests/com/google/gerrit/server/logging/MetadataTest.java
index 89e5690..f9ae2c1 100644
--- a/javatests/com/google/gerrit/server/logging/MetadataTest.java
+++ b/javatests/com/google/gerrit/server/logging/MetadataTest.java
@@ -23,7 +23,7 @@
   @Test
   public void stringForLoggingOmitsEmptyOptionalValuesAndReformatsOptionalValuesThatArePresent() {
     Metadata metadata = Metadata.builder().accountId(1000001).branchName("refs/heads/foo").build();
-    assertThat(metadata.toStringForLogging())
+    assertThat(metadata.toStringForLoggingLazy().evaluate())
         .isEqualTo("Metadata{accountId=1000001, branchName=refs/heads/foo, pluginMetadata=[]}");
   }
 
@@ -31,6 +31,7 @@
   public void
       stringForLoggingOmitsEmptyOptionalValuesAndReformatsOptionalValuesThatArePresentNoFieldsSet() {
     Metadata metadata = Metadata.builder().build();
-    assertThat(metadata.toStringForLogging()).isEqualTo("Metadata{pluginMetadata=[]}");
+    assertThat(metadata.toStringForLoggingLazy().evaluate())
+        .isEqualTo("Metadata{pluginMetadata=[]}");
   }
 }
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
index e8297af..2994c8d 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.html
@@ -121,10 +121,6 @@
       .changeMetadata {
         border-right: 1px solid var(--border-color);
       }
-      /* Prevent plugin text from overflowing. */
-      #change_plugins {
-        word-break: break-word;
-      }
       .commitMessage {
         font-family: var(--monospace-font-family);
         margin-right: 1em;
@@ -438,10 +434,6 @@
               parent-is-current="[[_parentIsCurrent]]"
               on-show-reply-dialog="_handleShowReplyDialog">
           </gr-change-metadata>
-          <!-- Plugins insert content into following container.
-               Stop-gap until PolyGerrit plugins interface is ready.
-               This will not work with Shadow DOM. -->
-          <div id="change_plugins"></div>
         </div>
         <div id="mainChangeInfo" class="changeInfo-column mainChangeInfo">
           <div id="commitAndRelated" class="hideOnMobileOverlay">
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
index 9e6997c..180d1a3 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
@@ -303,11 +303,11 @@
     },
 
     _calculatePatchChange(files) {
-      const filesNoCommitMsg = files.filter(files => {
-        return files.__path !== '/COMMIT_MSG';
+      const magicFilesExcluded = files.filter(files => {
+        return files.__path !== '/COMMIT_MSG' && files.__path !== '/MERGE_LIST';
       });
 
-      return filesNoCommitMsg.reduce((acc, obj) => {
+      return magicFilesExcluded.reduce((acc, obj) => {
         const inserted = obj.lines_inserted ? obj.lines_inserted : 0;
         const deleted = obj.lines_deleted ? obj.lines_deleted : 0;
         const total_size = (obj.size && obj.binary) ? obj.size : 0;
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.html b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.html
index 3f95fd0..50e7701 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.html
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list_test.html
@@ -167,6 +167,9 @@
         '/COMMIT_MSG': {
           lines_inserted: 9,
         },
+        '/MERGE_LIST': {
+          lines_inserted: 9,
+        },
         'file_added_in_rev2.txt': {
           lines_inserted: 1,
           lines_deleted: 1,
@@ -200,6 +203,9 @@
         '/COMMIT_MSG': {
           lines_inserted: 9,
         },
+        '/MERGE_LIST': {
+          lines_inserted: 9,
+        },
         'myfile.txt': {
           lines_inserted: 1,
           lines_deleted: 1,
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js
index e3a4821..a18d2f4 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js
@@ -194,9 +194,13 @@
     },
 
     getTargetDiffElement() {
-      // Find the parent diff element of the cursor row.
-      for (let diff = this.diffRow; diff; diff = diff.parentElement) {
-        if (diff.tagName === 'GR-DIFF') { return diff; }
+      if (!this.diffRow) return null;
+
+      const hostOwner = Polymer.dom(/** @type {Node} */ (this.diffRow))
+        .getOwnerRoot();
+      if (hostOwner && hostOwner.host &&
+          hostOwner.host.tagName === 'GR-DIFF') {
+        return hostOwner.host;
       }
       return null;
     },
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html
index 7280f2f..ffb5efa 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html
@@ -249,6 +249,15 @@
       diffElement._diffChanged(mockDiffResponse.diffResponse);
     });
 
+    test('getTargetDiffElement', () => {
+      cursorElement.initialLineNumber = 1;
+      assert.isTrue(!!cursorElement.diffRow);
+      assert.equal(
+          cursorElement.getTargetDiffElement(),
+          diffElement
+      );
+    });
+
     test('getAddress', () => {
       // It should initialize to the first chunk: line 5 of the revision.
       assert.deepEqual(cursorElement.getAddress(),
diff --git a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.html b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.html
index 46877d7..1fa3db1 100644
--- a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.html
+++ b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.html
@@ -77,30 +77,13 @@
         on-blur="_onInputBlur"
         autocomplete="off">
 
-      <template is="dom-if" if="[[_isPolymer2()]]">
-        <!-- Content uses vertical-align:baseline. If iron-icon is placed
-          directly in the slot and is not visible,  vertical-align doesn't
-          work, because display:none convert it from inline-block element to
-          block element. To fix this problem, iron-icon is wrapped in div
-          which never changes display type.
-          The problem doesn't exist in Polymer1 because DOM is different.
-          Applying the same fix to Polymer1 breaks vertical-align.
-        -->
-        <div slot="prefix">
-          <iron-icon
-            icon="gr-icons:search"
-            class$="searchIcon [[_computeShowSearchIconClass(showSearchIcon)]]">
-          </iron-icon>
-        </div>
-      </template>
-      <template is="dom-if" if="[[!_isPolymer2()]]">
+      <!-- prefix as attribute is required to for polymer 1 -->
+      <div slot="prefix" prefix>
         <iron-icon
-          prefix
           icon="gr-icons:search"
           class$="searchIcon [[_computeShowSearchIconClass(showSearchIcon)]]">
         </iron-icon>
-      </template>
-
+      </div>
     </paper-input>
     <gr-autocomplete-dropdown
         vertical-align="top"
diff --git a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
index 745cff1..d422df8 100644
--- a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
+++ b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
@@ -196,7 +196,7 @@
     },
 
     focus() {
-      this.$.input.focus();
+      this._nativeInput.focus();
     },
 
     selectAll() {
@@ -330,7 +330,7 @@
         default:
           // For any normal keypress, return focus to the input to allow for
           // unbroken user input.
-          this.$.input.inputElement.focus();
+          this.focus();
 
           // Since this has been a normal keypress, the suggestions will have
           // been based on a previous input. Clear them. This prevents an
@@ -430,9 +430,5 @@
     _computeShowSearchIconClass(showSearchIcon) {
       return showSearchIcon ? 'showSearchIcon' : '';
     },
-
-    _isPolymer2() {
-      return window.POLYMER2;
-    },
   });
 })();
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js
new file mode 100644
index 0000000..cf2376e
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils.js
@@ -0,0 +1,95 @@
+/**
+ * @license
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+(function(window) {
+  'use strict';
+
+  const PRELOADED_PROTOCOL = 'preloaded:';
+
+  let _restAPI;
+
+  const getRestAPI = () => {
+    if (!_restAPI) {
+      _restAPI = document.createElement('gr-rest-api-interface');
+    }
+    return _restAPI;
+  };
+
+  function getPluginNameFromUrl(url) {
+    if (!(url instanceof URL)) {
+      try {
+        url = new URL(url);
+      } catch (e) {
+        console.warn(e);
+        return null;
+      }
+    }
+    if (url.protocol === PRELOADED_PROTOCOL) {
+      return url.pathname;
+    }
+    const base = Gerrit.BaseUrlBehavior.getBaseUrl();
+    const pathname = url.pathname.replace(base, '');
+    // Site theme is server from predefined path.
+    if (pathname === '/static/gerrit-theme.html') {
+      return 'gerrit-theme';
+    } else if (!pathname.startsWith('/plugins')) {
+      console.warn('Plugin not being loaded from /plugins base path:',
+          url.href, '— Unable to determine name.');
+      return null;
+    }
+    // Pathname should normally look like this:
+    // /plugins/PLUGINNAME/static/SCRIPTNAME.html
+    // Or, for app/samples:
+    // /plugins/PLUGINNAME.html
+    return pathname.split('/')[2].split('.')[0];
+  }
+
+  // TODO (viktard): deprecate in favor of GrPluginRestApi.
+  function send(method, url, opt_callback, opt_payload) {
+    return getRestAPI().send(method, url, opt_payload).then(response => {
+      if (response.status < 200 || response.status >= 300) {
+        return response.text().then(text => {
+          if (text) {
+            return Promise.reject(text);
+          } else {
+            return Promise.reject(response.status);
+          }
+        });
+      } else {
+        return getRestAPI().getResponseObject(response);
+      }
+    }).then(response => {
+      if (opt_callback) {
+        opt_callback(response);
+      }
+      return response;
+    });
+  }
+
+  function resetInternalState() {
+    _restAPI = null;
+  }
+
+  window._apiUtils = {
+    getPluginNameFromUrl,
+    send,
+    getRestAPI,
+
+    // TEST only methods
+    resetInternalState,
+  };
+})(window);
\ No newline at end of file
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html
new file mode 100644
index 0000000..c407aa8
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html
@@ -0,0 +1,78 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2019 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<title>gr-api-interface</title>
+<script src="/test/common-test-setup.js"></script>
+<script src="/bower_components/webcomponentsjs/custom-elements-es5-adapter.js"></script>
+
+<script src="/bower_components/webcomponentsjs/webcomponents-lite.js"></script>
+<script src="/bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
+<link rel="import" href="gr-js-api-interface.html">
+
+<script>void(0);</script>
+
+<script>
+
+  const PRELOADED_PROTOCOL = 'preloaded:';
+
+  suite('gr-api-utils tests', () => {
+    suite('test getPluginNameFromUrl', () => {
+      const {getPluginNameFromUrl} = window._apiUtils;
+
+      test('with empty string', () => {
+        assert.equal(getPluginNameFromUrl(''), null);
+      });
+
+      test('with invalid url', () => {
+        assert.equal(getPluginNameFromUrl('test'), null);
+      });
+
+      test('with random invalid url', () => {
+        assert.equal(getPluginNameFromUrl('http://example.com'), null);
+        assert.equal(
+            getPluginNameFromUrl('http://example.com/static/a.html'),
+            null
+        );
+      });
+
+      test('with valid urls', () => {
+        assert.equal(
+            getPluginNameFromUrl('http://example.com/plugins/a.html'),
+            'a'
+        );
+        assert.equal(
+            getPluginNameFromUrl('http://example.com/plugins/a/static/t.html'),
+            'a'
+        );
+      });
+
+      test('with preloaded urls', () => {
+        assert.equal(getPluginNameFromUrl(`${PRELOADED_PROTOCOL}a`), 'a');
+      });
+
+      test('with gerrit-theme override', () => {
+        assert.equal(
+            getPluginNameFromUrl('http://example.com/static/gerrit-theme.html'),
+            'gerrit-theme'
+        );
+      });
+    });
+  });
+</script>
\ No newline at end of file
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit.js
new file mode 100644
index 0000000..8cdbcb7
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit.js
@@ -0,0 +1,280 @@
+/**
+ * @license
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+(function(window) {
+  'use strict';
+
+  /**
+   * Hash of loaded and installed plugins, name to Plugin object.
+   */
+  const _plugins = {};
+
+  /**
+   * Array of plugin URLs to be loaded, name to url.
+   */
+  let _pluginsPending = {};
+
+  let _pluginsInstalled = [];
+
+  let _pluginsPendingCount = -1;
+
+  const UNKNOWN_PLUGIN = 'unknown';
+  const PRELOADED_PROTOCOL = 'preloaded:';
+
+  const PLUGIN_LOADING_TIMEOUT_MS = 10000;
+
+  let _reporting;
+  const getReporting = () => {
+    if (!_reporting) {
+      _reporting = document.createElement('gr-reporting');
+    }
+    return _reporting;
+  };
+
+  // Import utils methods
+  const {
+      getPluginNameFromUrl,
+      send,
+      getRestAPI,
+      resetInternalState,
+  } = window._apiUtils;
+
+  const API_VERSION = '0.1';
+
+  window.Gerrit = window.Gerrit || {};
+  const Gerrit = window.Gerrit;
+
+  let _resolveAllPluginsLoaded = null;
+  let _allPluginsPromise = null;
+
+  Gerrit._endpoints = new GrPluginEndpoints();
+
+  // Provide reset plugins function to clear installed plugins between tests.
+  const app = document.querySelector('#app');
+  if (!app) {
+    // No gr-app found (running tests)
+    Gerrit._installPreloadedPlugins = installPreloadedPlugins;
+    Gerrit._flushPreinstalls = flushPreinstalls;
+    Gerrit._resetPlugins = () => {
+      _allPluginsPromise = null;
+      _pluginsInstalled = [];
+      _pluginsPending = {};
+      _pluginsPendingCount = -1;
+      _reporting = null;
+      _resolveAllPluginsLoaded = null;
+      resetInternalState();
+      Gerrit._endpoints = new GrPluginEndpoints();
+      for (const k of Object.keys(_plugins)) {
+        delete _plugins[k];
+      }
+    };
+  }
+
+  /**
+   * @deprecated Use plugin.styles().css(rulesStr) instead. Please, consult
+   * the documentation how to replace it accordingly.
+   */
+  Gerrit.css = function(rulesStr) {
+    console.warn('Gerrit.css(rulesStr) is deprecated!',
+        'Use plugin.styles().css(rulesStr)');
+    if (!Gerrit._customStyleSheet) {
+      const styleEl = document.createElement('style');
+      document.head.appendChild(styleEl);
+      Gerrit._customStyleSheet = styleEl.sheet;
+    }
+
+    const name = '__pg_js_api_class_' +
+        Gerrit._customStyleSheet.cssRules.length;
+    Gerrit._customStyleSheet.insertRule('.' + name + '{' + rulesStr + '}', 0);
+    return name;
+  };
+
+  Gerrit.install = function(callback, opt_version, opt_src) {
+    // HTML import polyfill adds __importElement pointing to the import tag.
+    const script = document.currentScript &&
+        (document.currentScript.__importElement || document.currentScript);
+
+    let src = opt_src || (script && script.src);
+    if (!src || src.startsWith('data:')) {
+      src = script && script.baseURI;
+    }
+    const name = getPluginNameFromUrl(src);
+
+    if (opt_version && opt_version !== API_VERSION) {
+      Gerrit._pluginInstallError(`Plugin ${name} install error: only version ` +
+          API_VERSION + ' is supported in PolyGerrit. ' + opt_version +
+          ' was given.');
+      return;
+    }
+
+    const existingPlugin = _plugins[name];
+    const plugin = existingPlugin || new Plugin(src);
+    try {
+      callback(plugin);
+      if (name) {
+        _plugins[name] = plugin;
+      }
+      if (!existingPlugin) {
+        Gerrit._pluginInstalled(src);
+      }
+    } catch (e) {
+      Gerrit._pluginInstallError(`${e.name}: ${e.message}`);
+    }
+  };
+
+  Gerrit.getLoggedIn = function() {
+    console.warn('Gerrit.getLoggedIn() is deprecated! ' +
+        'Use plugin.restApi().getLoggedIn()');
+    return document.createElement('gr-rest-api-interface').getLoggedIn();
+  };
+
+  Gerrit.get = function(url, callback) {
+    console.warn('.get() is deprecated! Use plugin.restApi().get()');
+    send('GET', url, callback);
+  };
+
+  Gerrit.post = function(url, payload, callback) {
+    console.warn('.post() is deprecated! Use plugin.restApi().post()');
+    send('POST', url, callback, payload);
+  };
+
+  Gerrit.put = function(url, payload, callback) {
+    console.warn('.put() is deprecated! Use plugin.restApi().put()');
+    send('PUT', url, callback, payload);
+  };
+
+  Gerrit.delete = function(url, opt_callback) {
+    console.warn('.delete() is deprecated! Use plugin.restApi().delete()');
+    return getRestAPI().send('DELETE', url).then(response => {
+      if (response.status !== 204) {
+        return response.text().then(text => {
+          if (text) {
+            return Promise.reject(text);
+          } else {
+            return Promise.reject(response.status);
+          }
+        });
+      }
+      if (opt_callback) {
+        opt_callback(response);
+      }
+      return response;
+    });
+  };
+
+  Gerrit.awaitPluginsLoaded = function() {
+    if (!_allPluginsPromise) {
+      if (Gerrit._arePluginsLoaded()) {
+        _allPluginsPromise = Promise.resolve();
+      } else {
+        let timeoutId;
+        _allPluginsPromise =
+          Promise.race([
+            new Promise(resolve => _resolveAllPluginsLoaded = resolve),
+            new Promise(resolve => timeoutId = setTimeout(
+                Gerrit._pluginLoadingTimeout, PLUGIN_LOADING_TIMEOUT_MS)),
+          ]).then(() => clearTimeout(timeoutId));
+      }
+    }
+    return _allPluginsPromise;
+  };
+
+  Gerrit._pluginLoadingTimeout = function() {
+    console.error(`Failed to load plugins: ${Object.keys(_pluginsPending)}`);
+    Gerrit._setPluginsPending([]);
+  };
+
+  Gerrit._setPluginsPending = function(plugins) {
+    _pluginsPending = plugins.reduce((o, url) => {
+      // TODO(viktard): Remove guard (@see Issue 8962)
+      o[getPluginNameFromUrl(url) || UNKNOWN_PLUGIN] = url;
+      return o;
+    }, {});
+    Gerrit._setPluginsCount(Object.keys(_pluginsPending).length);
+  };
+
+  Gerrit._setPluginsCount = function(count) {
+    _pluginsPendingCount = count;
+    if (Gerrit._arePluginsLoaded()) {
+      getReporting().pluginsLoaded(_pluginsInstalled);
+      if (_resolveAllPluginsLoaded) {
+        _resolveAllPluginsLoaded();
+      }
+    }
+  };
+
+  Gerrit._pluginInstallError = function(message) {
+    document.dispatchEvent(new CustomEvent('show-alert', {
+      detail: {
+        message: `Plugin install error: ${message}`,
+      },
+    }));
+    console.info(`Plugin install error: ${message}`);
+    Gerrit._setPluginsCount(_pluginsPendingCount - 1);
+  };
+
+  Gerrit._pluginInstalled = function(url) {
+    const name = getPluginNameFromUrl(url) || UNKNOWN_PLUGIN;
+    if (!_pluginsPending[name]) {
+      console.warn(`Unexpected plugin ${name} installed from ${url}.`);
+    } else {
+      delete _pluginsPending[name];
+      _pluginsInstalled.push(name);
+      Gerrit._setPluginsCount(_pluginsPendingCount - 1);
+      getReporting().pluginLoaded(name);
+      console.log(`Plugin ${name} installed.`);
+    }
+  };
+
+  Gerrit._arePluginsLoaded = function() {
+    return _pluginsPendingCount === 0;
+  };
+
+  Gerrit._getPluginScreenName = function(pluginName, screenName) {
+    return `${pluginName}-screen-${screenName}`;
+  };
+
+  Gerrit._isPluginPreloaded = function(url) {
+    const name = getPluginNameFromUrl(url);
+    if (name && Gerrit._preloadedPlugins) {
+      return name in Gerrit._preloadedPlugins;
+    } else {
+      return false;
+    }
+  };
+
+  function flushPreinstalls() {
+    if (window.Gerrit.flushPreinstalls) {
+      window.Gerrit.flushPreinstalls();
+    }
+  }
+
+  function installPreloadedPlugins() {
+    if (!Gerrit._preloadedPlugins) { return; }
+    for (const name in Gerrit._preloadedPlugins) {
+      if (!Gerrit._preloadedPlugins.hasOwnProperty(name)) { continue; }
+      const callback = Gerrit._preloadedPlugins[name];
+      Gerrit.install(callback, API_VERSION, PRELOADED_PROTOCOL + name);
+    }
+  }
+
+  flushPreinstalls();
+
+  // Preloaded plugins should be installed after Gerrit.install() is set,
+  // since plugin preloader substitutes Gerrit.install() temporarily.
+  installPreloadedPlugins();
+})(window);
\ No newline at end of file
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit_test.html
new file mode 100644
index 0000000..b3ec30f
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-gerrit_test.html
@@ -0,0 +1,188 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2019 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<title>gr-api-interface</title>
+<script src="/test/common-test-setup.js"></script>
+<script src="/bower_components/webcomponentsjs/custom-elements-es5-adapter.js"></script>
+
+<script src="/bower_components/webcomponentsjs/webcomponents-lite.js"></script>
+<script src="/bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
+<link rel="import" href="gr-js-api-interface.html">
+
+<script>void(0);</script>
+
+<test-fixture id="basic">
+  <template>
+    <gr-js-api-interface></gr-js-api-interface>
+  </template>
+</test-fixture>
+
+<script>
+  suite('gr-gerrit tests', () => {
+    let element;
+    let plugin;
+    let sandbox;
+    let sendStub;
+
+    setup(() => {
+      sandbox = sinon.sandbox.create();
+      sendStub = sandbox.stub().returns(Promise.resolve({status: 200}));
+      stub('gr-rest-api-interface', {
+        getAccount() {
+          return Promise.resolve({name: 'Judy Hopps'});
+        },
+        send(...args) {
+          return sendStub(...args);
+        },
+      });
+      element = fixture('basic');
+      Gerrit.install(p => { plugin = p; }, '0.1',
+          'http://test.com/plugins/testplugin/static/test.js');
+      Gerrit._setPluginsPending([]);
+    });
+
+    teardown(() => {
+      sandbox.restore();
+      element._removeEventCallbacks();
+      plugin = null;
+    });
+
+    test('reuse plugin for install calls', () => {
+      let otherPlugin;
+      Gerrit.install(p => { otherPlugin = p; }, '0.1',
+          'http://test.com/plugins/testplugin/static/test.js');
+      assert.strictEqual(plugin, otherPlugin);
+    });
+
+    test('flushes preinstalls if provided', () => {
+      assert.doesNotThrow(() => {
+        Gerrit._flushPreinstalls();
+      });
+      window.Gerrit.flushPreinstalls = sandbox.stub();
+      Gerrit._flushPreinstalls();
+      assert.isTrue(window.Gerrit.flushPreinstalls.calledOnce);
+      delete window.Gerrit.flushPreinstalls;
+    });
+
+    test('versioning', () => {
+      const callback = sandbox.spy();
+      Gerrit.install(callback, '0.0pre-alpha');
+      assert(callback.notCalled);
+    });
+
+    test('_setPluginsCount', done => {
+      stub('gr-reporting', {
+        pluginsLoaded() {
+          done();
+        },
+      });
+      Gerrit._setPluginsCount(0);
+    });
+
+    test('_arePluginsLoaded', () => {
+      assert.isTrue(Gerrit._arePluginsLoaded());
+      Gerrit._setPluginsCount(1);
+      assert.isFalse(Gerrit._arePluginsLoaded());
+      Gerrit._setPluginsCount(0);
+      assert.isTrue(Gerrit._arePluginsLoaded());
+    });
+
+    test('_pluginInstalled', () => {
+      const pluginsLoadedStub = sandbox.stub();
+      stub('gr-reporting', {
+        pluginsLoaded: (...args) => pluginsLoadedStub(...args),
+      });
+      const plugins = [
+        'http://test.com/plugins/foo/static/test.js',
+        'http://test.com/plugins/bar/static/test.js',
+      ];
+      Gerrit._setPluginsPending(plugins);
+      Gerrit._pluginInstalled(plugins[0]);
+      Gerrit._pluginInstalled(plugins[1]);
+      assert.isTrue(pluginsLoadedStub.calledWithExactly(['foo', 'bar']));
+    });
+
+    test('install calls _pluginInstalled', () => {
+      sandbox.stub(Gerrit, '_pluginInstalled');
+      Gerrit.install(p => { plugin = p; }, '0.1',
+          'http://test.com/plugins/testplugin/static/test.js');
+
+      // testplugin has already been installed once (in setup).
+      assert.isFalse(Gerrit._pluginInstalled.called);
+
+      // testplugin2 plugin has not yet been installed.
+      Gerrit.install(p => { plugin = p; }, '0.1',
+          'http://test.com/plugins/testplugin2/static/test.js');
+      assert.isTrue(Gerrit._pluginInstalled.calledOnce);
+    });
+
+    test('plugin install errors mark plugins as loaded', () => {
+      Gerrit._setPluginsCount(1);
+      Gerrit.install(() => {}, '0.0pre-alpha');
+      return Gerrit.awaitPluginsLoaded();
+    });
+
+    test('multiple ui plugins per java plugin', () => {
+      const file1 = 'http://test.com/plugins/qaz/static/foo.nocache.js';
+      const file2 = 'http://test.com/plugins/qaz/static/bar.js';
+      Gerrit._setPluginsPending([file1, file2]);
+      Gerrit.install(() => {}, '0.1', file1);
+      Gerrit.install(() => {}, '0.1', file2);
+      return Gerrit.awaitPluginsLoaded();
+    });
+
+    test('plugin install errors shows toasts', () => {
+      const alertStub = sandbox.stub();
+      document.addEventListener('show-alert', alertStub);
+      Gerrit._setPluginsCount(1);
+      Gerrit.install(() => {}, '0.0pre-alpha');
+      return Gerrit.awaitPluginsLoaded().then(() => {
+        assert.isTrue(alertStub.calledOnce);
+      });
+    });
+
+    test('Gerrit._isPluginPreloaded', () => {
+      Gerrit._preloadedPlugins = {baz: ()=>{}};
+      assert.isFalse(Gerrit._isPluginPreloaded('plugins/foo/bar'));
+      assert.isFalse(Gerrit._isPluginPreloaded('http://a.com/42'));
+      assert.isTrue(Gerrit._isPluginPreloaded('preloaded:baz'));
+      Gerrit._preloadedPlugins = null;
+    });
+
+    test('preloaded plugins are installed', () => {
+      const installStub = sandbox.stub();
+      Gerrit._preloadedPlugins = {foo: installStub};
+      Gerrit._installPreloadedPlugins();
+      assert.isTrue(installStub.called);
+      const pluginApi = installStub.lastCall.args[0];
+      assert.strictEqual(pluginApi.getPluginName(), 'foo');
+    });
+
+    test('installing preloaded plugin', () => {
+      let plugin;
+      window.ASSETS_PATH = 'http://blips.com/chitz';
+      Gerrit.install(p => { plugin = p; }, '0.1', 'preloaded:foo');
+      assert.strictEqual(plugin.getPluginName(), 'foo');
+      assert.strictEqual(plugin.url('/some/thing.html'),
+          'http://blips.com/chitz/plugins/foo/some/thing.html');
+      delete window.ASSETS_PATH;
+    });
+  });
+</script>
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.html
index e460660..7fa2250 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.html
@@ -31,6 +31,7 @@
 <link rel="import" href="../gr-rest-api-interface/gr-rest-api-interface.html">
 
 <dom-module id="gr-js-api-interface">
+  <script src="gr-api-utils.js"></script>
   <script src="gr-annotation-actions-context.js"></script>
   <script src="gr-annotation-actions-js-api.js"></script>
   <script src="gr-change-actions-js-api.js"></script>
@@ -40,4 +41,5 @@
   <script src="gr-plugin-action-context.js"></script>
   <script src="gr-plugin-rest-api.js"></script>
   <script src="gr-public-js-api.js"></script>
+  <script src="gr-gerrit.js"></script>
 </dom-module>
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
index c7e4f09..330310f 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
@@ -73,23 +73,6 @@
       plugin = null;
     });
 
-    test('reuse plugin for install calls', () => {
-      let otherPlugin;
-      Gerrit.install(p => { otherPlugin = p; }, '0.1',
-          'http://test.com/plugins/testplugin/static/test.js');
-      assert.strictEqual(plugin, otherPlugin);
-    });
-
-    test('flushes preinstalls if provided', () => {
-      assert.doesNotThrow(() => {
-        Gerrit._flushPreinstalls();
-      });
-      window.Gerrit.flushPreinstalls = sandbox.stub();
-      Gerrit._flushPreinstalls();
-      assert.isTrue(window.Gerrit.flushPreinstalls.calledOnce);
-      delete window.Gerrit.flushPreinstalls;
-    });
-
     test('url', () => {
       assert.equal(plugin.url(), 'http://test.com/plugins/testplugin/');
       assert.equal(plugin.url('/static/test.js'),
@@ -313,12 +296,6 @@
       element.handleEvent(element.EventType.HIGHLIGHTJS_LOADED, {hljs: testHljs});
     });
 
-    test('versioning', () => {
-      const callback = sandbox.spy();
-      Gerrit.install(callback, '0.0pre-alpha');
-      assert(callback.notCalled);
-    });
-
     test('getAccount', done => {
       plugin.restApi().getLoggedIn().then(loggedIn => {
         assert.isTrue(loggedIn);
@@ -326,77 +303,6 @@
       });
     });
 
-    test('_setPluginsCount', done => {
-      stub('gr-reporting', {
-        pluginsLoaded() {
-          done();
-        },
-      });
-      Gerrit._setPluginsCount(0);
-    });
-
-    test('_arePluginsLoaded', () => {
-      assert.isTrue(Gerrit._arePluginsLoaded());
-      Gerrit._setPluginsCount(1);
-      assert.isFalse(Gerrit._arePluginsLoaded());
-      Gerrit._setPluginsCount(0);
-      assert.isTrue(Gerrit._arePluginsLoaded());
-    });
-
-    test('_pluginInstalled', () => {
-      const pluginsLoadedStub = sandbox.stub();
-      stub('gr-reporting', {
-        pluginsLoaded: (...args) => pluginsLoadedStub(...args),
-      });
-      const plugins = [
-        'http://test.com/plugins/foo/static/test.js',
-        'http://test.com/plugins/bar/static/test.js',
-      ];
-      Gerrit._setPluginsPending(plugins);
-      Gerrit._pluginInstalled(plugins[0]);
-      Gerrit._pluginInstalled(plugins[1]);
-      assert.isTrue(pluginsLoadedStub.calledWithExactly(['foo', 'bar']));
-    });
-
-    test('install calls _pluginInstalled', () => {
-      sandbox.stub(Gerrit, '_pluginInstalled');
-      Gerrit.install(p => { plugin = p; }, '0.1',
-          'http://test.com/plugins/testplugin/static/test.js');
-
-      // testplugin has already been installed once (in setup).
-      assert.isFalse(Gerrit._pluginInstalled.called);
-
-      // testplugin2 plugin has not yet been installed.
-      Gerrit.install(p => { plugin = p; }, '0.1',
-          'http://test.com/plugins/testplugin2/static/test.js');
-      assert.isTrue(Gerrit._pluginInstalled.calledOnce);
-    });
-
-    test('plugin install errors mark plugins as loaded', () => {
-      Gerrit._setPluginsCount(1);
-      Gerrit.install(() => {}, '0.0pre-alpha');
-      return Gerrit.awaitPluginsLoaded();
-    });
-
-    test('multiple ui plugins per java plugin', () => {
-      const file1 = 'http://test.com/plugins/qaz/static/foo.nocache.js';
-      const file2 = 'http://test.com/plugins/qaz/static/bar.js';
-      Gerrit._setPluginsPending([file1, file2]);
-      Gerrit.install(() => {}, '0.1', file1);
-      Gerrit.install(() => {}, '0.1', file2);
-      return Gerrit.awaitPluginsLoaded();
-    });
-
-    test('plugin install errors shows toasts', () => {
-      const alertStub = sandbox.stub();
-      document.addEventListener('show-alert', alertStub);
-      Gerrit._setPluginsCount(1);
-      Gerrit.install(() => {}, '0.0pre-alpha');
-      return Gerrit.awaitPluginsLoaded().then(() => {
-        assert.isTrue(alertStub.calledOnce);
-      });
-    });
-
     test('attributeHelper', () => {
       assert.isOk(plugin.attributeHelper());
     });
@@ -422,33 +328,6 @@
           element.EventType.ADMIN_MENU_LINKS);
     });
 
-    test('Gerrit._isPluginPreloaded', () => {
-      Gerrit._preloadedPlugins = {baz: ()=>{}};
-      assert.isFalse(Gerrit._isPluginPreloaded('plugins/foo/bar'));
-      assert.isFalse(Gerrit._isPluginPreloaded('http://a.com/42'));
-      assert.isTrue(Gerrit._isPluginPreloaded('preloaded:baz'));
-      Gerrit._preloadedPlugins = null;
-    });
-
-    test('preloaded plugins are installed', () => {
-      const installStub = sandbox.stub();
-      Gerrit._preloadedPlugins = {foo: installStub};
-      Gerrit._installPreloadedPlugins();
-      assert.isTrue(installStub.called);
-      const pluginApi = installStub.lastCall.args[0];
-      assert.strictEqual(pluginApi.getPluginName(), 'foo');
-    });
-
-    test('installing preloaded plugin', () => {
-      let plugin;
-      window.ASSETS_PATH = 'http://blips.com/chitz';
-      Gerrit.install(p => { plugin = p; }, '0.1', 'preloaded:foo');
-      assert.strictEqual(plugin.getPluginName(), 'foo');
-      assert.strictEqual(plugin.url('/some/thing.html'),
-          'http://blips.com/chitz/plugins/foo/some/thing.html');
-      delete window.ASSETS_PATH;
-    });
-
     suite('test plugin with base url', () => {
       let baseUrlPlugin;
 
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
index 3b7b80d..d44acea 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
@@ -17,71 +17,18 @@
 (function(window) {
   'use strict';
 
-  /**
-   * Hash of loaded and installed plugins, name to Plugin object.
-   */
-  const _plugins = {};
-
-  /**
-   * Array of plugin URLs to be loaded, name to url.
-   */
-  let _pluginsPending = {};
-
-  let _pluginsInstalled = [];
-
-  let _pluginsPendingCount = -1;
-
   const PRELOADED_PROTOCOL = 'preloaded:';
 
-  const UNKNOWN_PLUGIN = 'unknown';
-
   const PANEL_ENDPOINTS_MAPPING = {
     CHANGE_SCREEN_BELOW_COMMIT_INFO_BLOCK: 'change-view-integration',
     CHANGE_SCREEN_BELOW_CHANGE_INFO_BLOCK: 'change-metadata-item',
   };
 
-  const PLUGIN_LOADING_TIMEOUT_MS = 10000;
-
-  let _restAPI;
-
-  const getRestAPI = () => {
-    if (!_restAPI) {
-      _restAPI = document.createElement('gr-rest-api-interface');
-    }
-    return _restAPI;
-  };
-
-  let _reporting;
-  const getReporting = () => {
-    if (!_reporting) {
-      _reporting = document.createElement('gr-reporting');
-    }
-    return _reporting;
-  };
-
-  // TODO (viktard): deprecate in favor of GrPluginRestApi.
-  function send(method, url, opt_callback, opt_payload) {
-    return getRestAPI().send(method, url, opt_payload).then(response => {
-      if (response.status < 200 || response.status >= 300) {
-        return response.text().then(text => {
-          if (text) {
-            return Promise.reject(text);
-          } else {
-            return Promise.reject(response.status);
-          }
-        });
-      } else {
-        return getRestAPI().getResponseObject(response);
-      }
-    }).then(response => {
-      if (opt_callback) {
-        opt_callback(response);
-      }
-      return response;
-    });
-  }
-
-  const API_VERSION = '0.1';
+  // Import utils methods
+  const {
+      getPluginNameFromUrl,
+      send,
+  } = window._apiUtils;
 
   /**
    * Plugin-provided custom components can affect content in extension
@@ -99,50 +46,6 @@
     STYLE: 'style',
   };
 
-  function flushPreinstalls() {
-    if (window.Gerrit.flushPreinstalls) {
-      window.Gerrit.flushPreinstalls();
-    }
-  }
-
-  function installPreloadedPlugins() {
-    if (!Gerrit._preloadedPlugins) { return; }
-    for (const name in Gerrit._preloadedPlugins) {
-      if (!Gerrit._preloadedPlugins.hasOwnProperty(name)) { continue; }
-      const callback = Gerrit._preloadedPlugins[name];
-      Gerrit.install(callback, API_VERSION, PRELOADED_PROTOCOL + name);
-    }
-  }
-
-  function getPluginNameFromUrl(url) {
-    if (!(url instanceof URL)) {
-      try {
-        url = new URL(url);
-      } catch (e) {
-        console.warn(e);
-        return null;
-      }
-    }
-    if (url.protocol === PRELOADED_PROTOCOL) {
-      return url.pathname;
-    }
-    const base = Gerrit.BaseUrlBehavior.getBaseUrl();
-    const pathname = url.pathname.replace(base, '');
-    // Site theme is server from predefined path.
-    if (pathname === '/static/gerrit-theme.html') {
-      return 'gerrit-theme';
-    } else if (!pathname.startsWith('/plugins')) {
-      console.warn('Plugin not being loaded from /plugins base path:',
-          url.href, '— Unable to determine name.');
-      return;
-    }
-    // Pathname should normally look like this:
-    // /plugins/PLUGINNAME/static/SCRIPTNAME.html
-    // Or, for app/samples:
-    // /plugins/PLUGINNAME.html
-    return pathname.split('/')[2].split('.')[0];
-  }
-
   function Plugin(opt_url) {
     this._domHooks = new GrDomHooksManager(this);
 
@@ -475,211 +378,5 @@
     },
   };
 
-  flushPreinstalls();
-
-  window.Gerrit = window.Gerrit || {};
-  const Gerrit = window.Gerrit;
-
-  let _resolveAllPluginsLoaded = null;
-  let _allPluginsPromise = null;
-
-  Gerrit._endpoints = new GrPluginEndpoints();
-
-  // Provide reset plugins function to clear installed plugins between tests.
-  const app = document.querySelector('#app');
-  if (!app) {
-    // No gr-app found (running tests)
-    Gerrit._installPreloadedPlugins = installPreloadedPlugins;
-    Gerrit._flushPreinstalls = flushPreinstalls;
-    Gerrit._resetPlugins = () => {
-      _allPluginsPromise = null;
-      _pluginsInstalled = [];
-      _pluginsPending = {};
-      _pluginsPendingCount = -1;
-      _reporting = null;
-      _resolveAllPluginsLoaded = null;
-      _restAPI = null;
-      Gerrit._endpoints = new GrPluginEndpoints();
-      for (const k of Object.keys(_plugins)) {
-        delete _plugins[k];
-      }
-    };
-  }
-
-  /**
-   * @deprecated Use plugin.styles().css(rulesStr) instead. Please, consult
-   * the documentation how to replace it accordingly.
-   */
-  Gerrit.css = function(rulesStr) {
-    console.warn('Gerrit.css(rulesStr) is deprecated!',
-        'Use plugin.styles().css(rulesStr)');
-    if (!Gerrit._customStyleSheet) {
-      const styleEl = document.createElement('style');
-      document.head.appendChild(styleEl);
-      Gerrit._customStyleSheet = styleEl.sheet;
-    }
-
-    const name = '__pg_js_api_class_' +
-        Gerrit._customStyleSheet.cssRules.length;
-    Gerrit._customStyleSheet.insertRule('.' + name + '{' + rulesStr + '}', 0);
-    return name;
-  };
-
-  Gerrit.install = function(callback, opt_version, opt_src) {
-    // HTML import polyfill adds __importElement pointing to the import tag.
-    const script = document.currentScript &&
-        (document.currentScript.__importElement || document.currentScript);
-
-    let src = opt_src || (script && script.src);
-    if (!src || src.startsWith('data:')) {
-      src = script && script.baseURI;
-    }
-    const name = getPluginNameFromUrl(src);
-
-    if (opt_version && opt_version !== API_VERSION) {
-      Gerrit._pluginInstallError(`Plugin ${name} install error: only version ` +
-          API_VERSION + ' is supported in PolyGerrit. ' + opt_version +
-          ' was given.');
-      return;
-    }
-
-    const existingPlugin = _plugins[name];
-    const plugin = existingPlugin || new Plugin(src);
-    try {
-      callback(plugin);
-      if (name) {
-        _plugins[name] = plugin;
-      }
-      if (!existingPlugin) {
-        Gerrit._pluginInstalled(src);
-      }
-    } catch (e) {
-      Gerrit._pluginInstallError(`${e.name}: ${e.message}`);
-    }
-  };
-
-  Gerrit.getLoggedIn = function() {
-    console.warn('Gerrit.getLoggedIn() is deprecated! ' +
-        'Use plugin.restApi().getLoggedIn()');
-    return document.createElement('gr-rest-api-interface').getLoggedIn();
-  };
-
-  Gerrit.get = function(url, callback) {
-    console.warn('.get() is deprecated! Use plugin.restApi().get()');
-    send('GET', url, callback);
-  };
-
-  Gerrit.post = function(url, payload, callback) {
-    console.warn('.post() is deprecated! Use plugin.restApi().post()');
-    send('POST', url, callback, payload);
-  };
-
-  Gerrit.put = function(url, payload, callback) {
-    console.warn('.put() is deprecated! Use plugin.restApi().put()');
-    send('PUT', url, callback, payload);
-  };
-
-  Gerrit.delete = function(url, opt_callback) {
-    console.warn('.delete() is deprecated! Use plugin.restApi().delete()');
-    return getRestAPI().send('DELETE', url).then(response => {
-      if (response.status !== 204) {
-        return response.text().then(text => {
-          if (text) {
-            return Promise.reject(text);
-          } else {
-            return Promise.reject(response.status);
-          }
-        });
-      }
-      if (opt_callback) {
-        opt_callback(response);
-      }
-      return response;
-    });
-  };
-
-  Gerrit.awaitPluginsLoaded = function() {
-    if (!_allPluginsPromise) {
-      if (Gerrit._arePluginsLoaded()) {
-        _allPluginsPromise = Promise.resolve();
-      } else {
-        let timeoutId;
-        _allPluginsPromise =
-          Promise.race([
-            new Promise(resolve => _resolveAllPluginsLoaded = resolve),
-            new Promise(resolve => timeoutId = setTimeout(
-                Gerrit._pluginLoadingTimeout, PLUGIN_LOADING_TIMEOUT_MS)),
-          ]).then(() => clearTimeout(timeoutId));
-      }
-    }
-    return _allPluginsPromise;
-  };
-
-  Gerrit._pluginLoadingTimeout = function() {
-    console.error(`Failed to load plugins: ${Object.keys(_pluginsPending)}`);
-    Gerrit._setPluginsPending([]);
-  };
-
-  Gerrit._setPluginsPending = function(plugins) {
-    _pluginsPending = plugins.reduce((o, url) => {
-      // TODO(viktard): Remove guard (@see Issue 8962)
-      o[getPluginNameFromUrl(url) || UNKNOWN_PLUGIN] = url;
-      return o;
-    }, {});
-    Gerrit._setPluginsCount(Object.keys(_pluginsPending).length);
-  };
-
-  Gerrit._setPluginsCount = function(count) {
-    _pluginsPendingCount = count;
-    if (Gerrit._arePluginsLoaded()) {
-      getReporting().pluginsLoaded(_pluginsInstalled);
-      if (_resolveAllPluginsLoaded) {
-        _resolveAllPluginsLoaded();
-      }
-    }
-  };
-
-  Gerrit._pluginInstallError = function(message) {
-    document.dispatchEvent(new CustomEvent('show-alert', {
-      detail: {
-        message: `Plugin install error: ${message}`,
-      },
-    }));
-    console.info(`Plugin install error: ${message}`);
-    Gerrit._setPluginsCount(_pluginsPendingCount - 1);
-  };
-
-  Gerrit._pluginInstalled = function(url) {
-    const name = getPluginNameFromUrl(url) || UNKNOWN_PLUGIN;
-    if (!_pluginsPending[name]) {
-      console.warn(`Unexpected plugin ${name} installed from ${url}.`);
-    } else {
-      delete _pluginsPending[name];
-      _pluginsInstalled.push(name);
-      Gerrit._setPluginsCount(_pluginsPendingCount - 1);
-      getReporting().pluginLoaded(name);
-      console.log(`Plugin ${name} installed.`);
-    }
-  };
-
-  Gerrit._arePluginsLoaded = function() {
-    return _pluginsPendingCount === 0;
-  };
-
-  Gerrit._getPluginScreenName = function(pluginName, screenName) {
-    return `${pluginName}-screen-${screenName}`;
-  };
-
-  Gerrit._isPluginPreloaded = function(url) {
-    const name = getPluginNameFromUrl(url);
-    if (name && Gerrit._preloadedPlugins) {
-      return name in Gerrit._preloadedPlugins;
-    } else {
-      return false;
-    }
-  };
-
-  // Preloaded plugins should be installed after Gerrit.install() is set,
-  // since plugin preloader substitutes Gerrit.install() temporarily.
-  installPreloadedPlugins();
+  window.Plugin = Plugin;
 })(window);
diff --git a/polygerrit-ui/app/test/index.html b/polygerrit-ui/app/test/index.html
index 10d5aff..a0e85ef 100644
--- a/polygerrit-ui/app/test/index.html
+++ b/polygerrit-ui/app/test/index.html
@@ -188,7 +188,9 @@
     'shared/gr-js-api-interface/gr-annotation-actions-js-api_test.html',
     'shared/gr-js-api-interface/gr-change-actions-js-api_test.html',
     'shared/gr-js-api-interface/gr-change-reply-js-api_test.html',
+    'shared/gr-js-api-interface/gr-api-utils_test.html',
     'shared/gr-js-api-interface/gr-js-api-interface_test.html',
+    'shared/gr-js-api-interface/gr-gerrit_test.html',
     // TODO: uncomment file & fix tests. The file was missed in this list for a long time.
     // 'shared/gr-js-api-interface/gr-plugin-action-context_test.html',
     'shared/gr-js-api-interface/gr-plugin-endpoints_test.html',
diff --git a/resources/com/google/gerrit/server/mime/mime-types.properties b/resources/com/google/gerrit/server/mime/mime-types.properties
index f12b39e..4229e4a 100644
--- a/resources/com/google/gerrit/server/mime/mime-types.properties
+++ b/resources/com/google/gerrit/server/mime/mime-types.properties
@@ -31,6 +31,7 @@
 cr = text/x-crystal
 cs = text/x-csharp
 csharp = text/x-csharp
+csproj = application/xml
 css = text/css
 cpp = text/x-c++src
 cql = text/x-cassandra
@@ -242,6 +243,7 @@
 vtl = text/velocity
 webidl = text/x-webidl
 wsdl = application/xml
+xaml = application/xml
 xhtml = text/html
 xml = application/xml
 xsd = application/xml