Merge branch 'stable-3.9' * stable-3.9: Rename config.md to metrics.md Add the ability to fail healthcheck by creating a fail file Introduce healthcheck extension Revert "Adapt list projects tests to ListProjectsImpl new type" Change-Id: I7be479009a730ab34bb4fb2409ed058580d5c238

diff --git a/BUILD b/BUILD
index e87843c..24a2d60 100644
--- a/BUILD
+++ b/BUILD

@@ -13,6 +13,7 @@
         "Gerrit-PluginName: healthcheck",
         "Gerrit-Module: com.googlesource.gerrit.plugins.healthcheck.Module",
         "Gerrit-HttpModule: com.googlesource.gerrit.plugins.healthcheck.HttpModule",
+        "Gerrit-ApiModule: com.googlesource.gerrit.plugins.healthcheck.HealthCheckExtensionApiModule",
     ],
     resources = glob(["src/main/resources/**/*"]),
 )

diff --git a/README.md b/README.md
index 8be0b33..bd49524 100644
--- a/README.md
+++ b/README.md

@@ -126,6 +126,25 @@
 }
 ```
 
+It's also possible to artificially make the healthcheck fail by placing a file
+at a configurable path specified like:
+
+```
+[healtcheck]
+  failFileFlaPath="data/healthcheck/fail"
+```
+
+This will make the healthcheck endpoint return 500 even if the node is otherwise
+healthy. This is useful when a node needs to be removed from the pool of
+available Gerrit instance while it undergoes maintenance.
+
+**NOTE**: If the path starts with `/` then even paths outside of Gerrit's home
+will be checked. If the path starts WITHOUT `/` then the path is relative to
+Gerrit's home.
+
+**NOTE**: The file needs to be a real file rather than a symlink.
+
+
 ## Metrics
 
 As for all other endpoints in Gerrit, some metrics are automatically emitted when the  `/config/server/healthcheck~status`
@@ -134,4 +153,4 @@
 Some additional metrics are also produced to give extra insights on their result about results and latency of healthcheck
 sub component, such as jgit, reviewdb, etc.
 
-More information can be found in the [config.md](resources/Documentation/config.md) file.
+More information can be found in the [metrics.md](resources/Documentation/metrics.md) file.

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java
index 651dbe9..1dc143c 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckConfig.java

@@ -47,6 +47,7 @@
   private static final int ACTIVE_WORKERS_THRESHOLD_DEFAULT = 80;
   private static final String USERNAME_DEFAULT = "healthcheck";
   private static final String PASSWORD_DEFAULT = "";
+  private static final String FAIL_FILE_FLAG_DEFAULT = "data/healthcheck/fail";
   private static final boolean HEALTH_CHECK_ENABLED_DEFAULT = true;
   private final AllProjectsName allProjectsName;
   private final AllUsersName allUsersName;
@@ -135,6 +136,10 @@
     return getStringWithFallback("password", healthCheckName, PASSWORD_DEFAULT);
   }
 
+  public String getFailFileFlagPath() {
+    return getStringWithFallback("failFileFlagPath", null, FAIL_FILE_FLAG_DEFAULT);
+  }
+
   public boolean healthCheckEnabled(String healthCheckName) {
     if (isReplica && HEALTH_CHECK_DISABLED_FOR_REPLICAS.contains(healthCheckName)) {
       return false;

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckModule.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckExtensionApiModule.java
similarity index 94%
rename from src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckModule.java
rename to src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckExtensionApiModule.java
index 0fa02f2..efa6be4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckExtensionApiModule.java

@@ -21,7 +21,7 @@
 import com.googlesource.gerrit.plugins.healthcheck.check.HealthCheck;
 import java.util.concurrent.Executors;
 
-public class HealthCheckModule extends AbstractModule {
+public class HealthCheckExtensionApiModule extends AbstractModule {
   public static final int CHECK_THREADS_DEFAULT = 10;
 
   @Override

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckMetrics.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckMetrics.java
index 1f88020..9635938 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckMetrics.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckMetrics.java

@@ -18,20 +18,13 @@
 import com.google.gerrit.metrics.Description;
 import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.metrics.Timer0;
-import com.google.inject.Inject;
-import com.google.inject.assistedinject.Assisted;
 
 public class HealthCheckMetrics {
 
-  public interface Factory {
-    HealthCheckMetrics create(String name);
-  }
-
   private final MetricMaker metricMaker;
   private final String name;
 
-  @Inject
-  public HealthCheckMetrics(MetricMaker metricMaker, @Assisted String name) {
+  public HealthCheckMetrics(MetricMaker metricMaker, String name) {
     this.metricMaker = metricMaker;
     this.name = name;
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java
index 3cda7b6..aea007a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckSubsystemsModule.java

@@ -37,7 +37,6 @@
     bindChecker(DeadlockCheck.class);
     bindChecker(BlockedThreadsCheck.class);
 
-    factory(HealthCheckMetrics.Factory.class);
     install(BlockedThreadsCheck.SUB_CHECKS);
   }
 

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/Module.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/Module.java
index 9508084..54cd5a0 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/Module.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/Module.java

@@ -20,7 +20,6 @@
 
   @Override
   protected void configure() {
-    install(new HealthCheckModule());
     install(new HealthCheckSubsystemsModule());
     install(new HealthCheckApiModule());
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/api/HealthCheckStatusEndpoint.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/api/HealthCheckStatusEndpoint.java
index 2d5f7de..6819ae1 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/api/HealthCheckStatusEndpoint.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/api/HealthCheckStatusEndpoint.java

@@ -18,9 +18,14 @@
 import com.google.gerrit.server.config.ConfigResource;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
+import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
 import com.googlesource.gerrit.plugins.healthcheck.check.GlobalHealthCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.HealthCheck;
 import com.googlesource.gerrit.plugins.healthcheck.check.HealthCheck.Result;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.util.Map;
 import javax.servlet.http.HttpServletResponse;
 
@@ -29,14 +34,21 @@
 
   private final GlobalHealthCheck healthChecks;
 
+  private final String failedFileFlagPath;
+
   @Inject
-  public HealthCheckStatusEndpoint(GlobalHealthCheck healthChecks) {
+  public HealthCheckStatusEndpoint(GlobalHealthCheck healthChecks, HealthCheckConfig config) {
     this.healthChecks = healthChecks;
+    this.failedFileFlagPath = config.getFailFileFlagPath();
   }
 
   @Override
   public Response<Map<String, Object>> apply(ConfigResource resource)
       throws AuthException, BadRequestException, ResourceConflictException, Exception {
+    if (failFlagFileExists()) {
+      return Response.withStatusCode(
+          HttpServletResponse.SC_INTERNAL_SERVER_ERROR, Map.of("reason", "Fail Flag File exists"));
+    }
     HealthCheck.StatusSummary globalHealthCheckStatus = healthChecks.run();
 
     Map<String, Object> result = globalHealthCheckStatus.subChecks;
@@ -50,4 +62,13 @@
         ? HttpServletResponse.SC_INTERNAL_SERVER_ERROR
         : HttpServletResponse.SC_OK;
   }
+
+  private boolean failFlagFileExists() throws IOException {
+    File file = new File(failedFileFlagPath);
+    try (InputStream targetStream = new FileInputStream(file)) {
+      return true;
+    } catch (Exception e) {
+      return false;
+    }
+  }
 }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AbstractHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AbstractHealthCheck.java
index 9e4544a..5a8246b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AbstractHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AbstractHealthCheck.java

@@ -17,6 +17,7 @@
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.metrics.Counter0;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.metrics.Timer0;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
@@ -42,14 +43,14 @@
       ListeningExecutorService executor,
       HealthCheckConfig config,
       String name,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
+      MetricMaker metricMaker) {
     this.executor = executor;
     this.name = name;
     this.timeout = config.getTimeout(name);
     this.config = config;
     this.latestStatus = StatusSummary.INITIAL_STATUS;
 
-    HealthCheckMetrics healthCheckMetrics = healthCheckMetricsFactory.create(name);
+    HealthCheckMetrics healthCheckMetrics = new HealthCheckMetrics(metricMaker, name);
     this.failureCounterMetric = healthCheckMetrics.getFailureCounterMetric();
     this.latencyMetric = healthCheckMetrics.getLatencyMetric();
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ActiveWorkersCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ActiveWorkersCheck.java
index 8e64593..8684ef8 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ActiveWorkersCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ActiveWorkersCheck.java

@@ -18,11 +18,11 @@
 
 import com.codahale.metrics.MetricRegistry;
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.ThreadSettingsConfig;
 import com.google.inject.Inject;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.Optional;
 import org.eclipse.jgit.lib.Config;
 
@@ -42,8 +42,8 @@
       HealthCheckConfig healthCheckConfig,
       ThreadSettingsConfig threadSettingsConfig,
       MetricRegistry metricRegistry,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, healthCheckConfig, ACTIVEWORKERS, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, healthCheckConfig, ACTIVEWORKERS, metricMaker);
     this.threshold = healthCheckConfig.getActiveWorkersThreshold(ACTIVEWORKERS);
     this.metricRegistry = metricRegistry;
     this.interactiveThreadsMaxPoolSize =

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java
index c2b0f3e..2dc22dc 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/AuthHealthCheck.java

@@ -17,6 +17,7 @@
 import static com.googlesource.gerrit.plugins.healthcheck.check.HealthCheckNames.AUTH;
 
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.AccountState;
 import com.google.gerrit.server.account.AuthRequest;
@@ -24,7 +25,6 @@
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.Optional;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -45,8 +45,8 @@
       Realm realm,
       AccountCache byIdCache,
       AuthRequest.Factory authRequestFactory,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, config, AUTH, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, config, AUTH, metricMaker);
 
     this.realm = realm;
     this.byIdCache = byIdCache;

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsCheck.java
index 78b8b01..1e282b3 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsCheck.java

@@ -19,12 +19,12 @@
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.extensions.config.FactoryModule;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.Inject;
 import com.google.inject.Module;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.lang.management.ManagementFactory;
 import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
@@ -50,10 +50,10 @@
   public BlockedThreadsCheck(
       ListeningExecutorService executor,
       HealthCheckConfig healthCheckConfig,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory,
+      MetricMaker metricMaker,
       ThreadBeanProvider threadBeanProvider,
       BlockedThreadsConfigurator checksConfig) {
-    super(executor, healthCheckConfig, BLOCKEDTHREADS, healthCheckMetricsFactory);
+    super(executor, healthCheckConfig, BLOCKEDTHREADS, metricMaker);
     this.threads = threadBeanProvider.get();
     this.collectorsSupplier = checksConfig;
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsSubCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsSubCheck.java
index d4f0fe8..7dcca27 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsSubCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/BlockedThreadsSubCheck.java

@@ -18,6 +18,7 @@
 
 import com.google.common.base.Strings;
 import com.google.gerrit.metrics.Counter0;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
@@ -65,11 +66,10 @@
 
   @Inject
   BlockedThreadsSubCheck(
-      HealthCheckMetrics.Factory healthCheckMetricsFactory,
-      @Assisted String prefix,
-      @Assisted Integer threshold) {
+      MetricMaker metricMaker, @Assisted String prefix, @Assisted Integer threshold) {
     HealthCheckMetrics healthCheckMetrics =
-        healthCheckMetricsFactory.create(
+        new HealthCheckMetrics(
+            metricMaker,
             String.format(
                 "%s-%s", BLOCKEDTHREADS, prefix.toLowerCase().replaceAll("[^\\w-/]", "_")));
     Counter0 failureCounterMetric = healthCheckMetrics.getFailureCounterMetric();

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/DeadlockCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/DeadlockCheck.java
index 6a6ade6..3d4b672 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/DeadlockCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/DeadlockCheck.java

@@ -18,9 +18,9 @@
 
 import com.codahale.metrics.MetricRegistry;
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.Inject;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.Optional;
 
 public class DeadlockCheck extends AbstractHealthCheck {
@@ -35,8 +35,8 @@
       ListeningExecutorService executor,
       HealthCheckConfig healthCheckConfig,
       MetricRegistry metricRegistry,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, healthCheckConfig, DEADLOCK, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, healthCheckConfig, DEADLOCK, metricMaker);
     this.metricRegistry = metricRegistry;
   }
 

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GlobalHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GlobalHealthCheck.java
index b004eaa..fa5f14a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GlobalHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/GlobalHealthCheck.java

@@ -18,10 +18,10 @@
 
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.extensions.registration.DynamicSet;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
@@ -38,8 +38,8 @@
       DynamicSet<HealthCheck> healthChecks,
       ListeningExecutorService executor,
       HealthCheckConfig healthCheckConfig,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, healthCheckConfig, GLOBAL, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, healthCheckConfig, GLOBAL, metricMaker);
     this.healthChecks = healthChecks;
   }
 

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/JGitHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/JGitHealthCheck.java
index 9196cdb..8fd60e5 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/JGitHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/JGitHealthCheck.java

@@ -18,11 +18,11 @@
 
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.Set;
 import org.eclipse.jgit.lib.Repository;
 
@@ -36,8 +36,8 @@
       ListeningExecutorService executor,
       HealthCheckConfig config,
       GitRepositoryManager repositoryManager,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, config, JGIT, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, config, JGIT, metricMaker);
     this.repositoryManager = repositoryManager;
     this.repositoryNameKeys = config.getJGITRepositories(JGIT);
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ProjectsListHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ProjectsListHealthCheck.java
index 78cff2a..d448cf4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ProjectsListHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/ProjectsListHealthCheck.java

@@ -18,6 +18,7 @@
 
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.extensions.common.ProjectInfo;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.restapi.project.ListProjects;
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
@@ -25,7 +26,6 @@
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.SortedMap;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -43,8 +43,8 @@
       HealthCheckConfig config,
       Provider<ListProjects> listProjectsProvider,
       OneOffRequestContext oneOffCtx,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, config, PROJECTSLIST, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, config, PROJECTSLIST, metricMaker);
 
     this.listProjectsProvider = listProjectsProvider;
     this.oneOffCtx = oneOffCtx;

diff --git a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/QueryChangesHealthCheck.java b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/QueryChangesHealthCheck.java
index a786606..7165b9f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/QueryChangesHealthCheck.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/healthcheck/check/QueryChangesHealthCheck.java

@@ -17,6 +17,7 @@
 import static com.googlesource.gerrit.plugins.healthcheck.check.HealthCheckNames.QUERYCHANGES;
 
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.restapi.change.QueryChanges;
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
@@ -24,7 +25,6 @@
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
-import com.googlesource.gerrit.plugins.healthcheck.HealthCheckMetrics;
 import java.util.List;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -42,8 +42,8 @@
       HealthCheckConfig config,
       Provider<QueryChanges> queryChangesProvider,
       OneOffRequestContext oneOffCtx,
-      HealthCheckMetrics.Factory healthCheckMetricsFactory) {
-    super(executor, config, QUERYCHANGES, healthCheckMetricsFactory);
+      MetricMaker metricMaker) {
+    super(executor, config, QUERYCHANGES, metricMaker);
     this.queryChangesProvider = queryChangesProvider;
     this.config = config;
     this.limit = config.getLimit(QUERYCHANGES);

diff --git a/src/main/resources/Documentation/extensions.md b/src/main/resources/Documentation/extensions.md
new file mode 100644
index 0000000..ccc07c7
--- /dev/null
+++ b/src/main/resources/Documentation/extensions.md

@@ -0,0 +1,129 @@
+# Custom checks extensions
+
+The @PLUGIN@ plugin allows other plugins to provide their own custom check that
+should participate in the definition of healthiness of the node.
+
+Plugins that are interested in doing so, will need to add a dependency on the
+healthcheck plugin, for example, their `BUILD` file could be as such:
+
+```
+gerrit_plugin(
+    name = "plugin-foo",
+    srcs = glob(["src/main/java/**/*.java"]),
+    manifest_entries = [
+        "Implementation-Title: Foo plugin",
+        "Implementation-URL: https://gerrit-review.googlesource.com/#/admin/projects/plugins/foo",
+        "Gerrit-PluginName: foo",
+        "Gerrit-Module: com.googlesource.gerrit.plugins.foo.Module",
+    ],
+    resources = glob(["src/main/resources/**/*"]),
+    deps = [
+        "gerrit-healthcheck-neverlink",
+    ],
+)
+
+java_library(
+    name = "gerrit-healthcheck-neverlink",
+    neverlink = True,
+    exports = ["//plugins/healthcheck"],
+)
+```
+
+Then, the plugin can provide its own healthcheck logic via a concrete
+implementation of an `AbstractHealthCheck`, for example:
+
+```java
+
+@Singleton
+public class FooHealthCheck extends AbstractHealthCheck {
+
+    @Inject
+    public FooHealthCheck(
+            ListeningExecutorService executor,
+            HealthCheckConfig config,
+            @PluginName String name,
+            MetricMaker metricMaker) {
+        super(executor, config, name, metricMaker);
+    }
+
+    @Override
+    protected Result doCheck() throws Exception {
+        // health logic goes here
+        return Result.PASSED;
+    }
+}
+```
+
+To build the plugin in the gerrit-CI, as
+[documented](https://gerrit-review.googlesource.com/Documentation/dev-plugins.html#_cross_plugin_communication)
+by gerrit, you should be configuring your build job as follows:
+
+```yaml
+- project:
+    name: plugin-foo
+    jobs:
+      - 'plugin-{name}-bazel-{branch}':
+          extra-plugins: 'healthcheck'
+          branch:
+            - master
+```
+
+To get the CI to validate your plugin you should also add the dependency to
+your `Jenkinsfile`:
+
+```
+pluginPipeline(
+  formatCheckId: 'gerritforge:foo-format-3852e64366bb37d13b8baf8af9b15cfd38eb9227',
+  buildCheckId: 'gerritforge:foo-3852e64366bb37d13b8baf8af9b15cfd38eb9227',
+  extraPlugins: ['healthcheck'])
+```
+
+Hitting the healthcheck status endpoint will now report the `foo` check,
+where `foo` is the name of the plugin, as defined in its manifest:
+
+```shell
+curl -v 'http://gerrit:8080/config/server/healthcheck~status'
+
+{
+  "elapsed": 18,
+  "foo": {
+    "result": "passed",
+    "ts": 1683723806276,
+    "elapsed": 0
+  },
+  "auth": {
+    "result": "passed",
+    "ts": 1683723806269,
+    "elapsed": 4
+  },
+  "querychanges": {
+    "result": "passed",
+    "ts": 1683723806266,
+    "elapsed": 3
+  },
+  "jgit": {
+    "result": "passed",
+    "ts": 1683723806258,
+    "elapsed": 7
+  },
+  "projectslist": {
+    "result": "passed",
+    "ts": 1683723806265,
+    "elapsed": 1
+  },
+  "ts": 1683723806258
+}
+```
+
+and the metrics for such component will also be reported, out of the box.
+
+```shell
+foo_latest_latency{quantile="0.5",} 0.008638662
+foo_latest_latency{quantile="0.75",} 0.008638662
+foo_latest_latency{quantile="0.95",} 0.010553707
+foo_latest_latency{quantile="0.98",} 0.147902061
+foo_latest_latency{quantile="0.99",} 0.147902061
+foo_latest_latency{quantile="0.999",} 0.147902061
+foo_latest_latency_count 4.0
+foo_failure_total 0.0
+```

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/AbstractHealthCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/AbstractHealthCheckTest.java
index fada3bb..a874739 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/AbstractHealthCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/AbstractHealthCheckTest.java

@@ -31,8 +31,7 @@
 
 public class AbstractHealthCheckTest {
 
-  MetricMaker testMetricMaker;
-  DummyHealthCheckMetricsFactory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
+  TestMetricMaker testMetricMaker;
 
   @Before
   public void setUp() throws Exception {
@@ -45,7 +44,6 @@
 
     testCheck.run();
 
-    TestMetricMaker testMetricMaker = healthCheckMetricsFactory.getMetricMaker();
     assertThat(testMetricMaker.getFailureCount()).isEqualTo(TestMetricMaker.expectedFailureCount);
     assertThat(testMetricMaker.getLatency()).isEqualTo(TestMetricMaker.expectedLatency);
   }
@@ -56,7 +54,6 @@
 
     testCheck.run();
 
-    TestMetricMaker testMetricMaker = healthCheckMetricsFactory.getMetricMaker();
     assertThat(testMetricMaker.getFailureCount()).isEqualTo(TestMetricMaker.expectedFailureCount);
     assertThat(testMetricMaker.getLatency()).isEqualTo(TestMetricMaker.expectedLatency);
   }
@@ -67,7 +64,6 @@
 
     testCheck.run();
 
-    TestMetricMaker testMetricMaker = healthCheckMetricsFactory.getMetricMaker();
     assertThat(testMetricMaker.getFailureCount()).isEqualTo(0L);
     assertThat(testMetricMaker.getLatency()).isEqualTo(TestMetricMaker.expectedLatency);
   }
@@ -78,7 +74,6 @@
 
     testCheck.run();
 
-    TestMetricMaker testMetricMaker = healthCheckMetricsFactory.getMetricMaker();
     assertThat(testMetricMaker.getFailureCount()).isEqualTo(0L);
     assertThat(testMetricMaker.getLatency()).isEqualTo(TestMetricMaker.expectedLatency);
   }
@@ -100,23 +95,19 @@
   }
 
   private TestCheck createTestCheckWithStatus(HealthCheck.Result result) {
-    return new TestCheck(
-        HealthCheckConfig.DEFAULT_CONFIG, "testCheck", healthCheckMetricsFactory, result);
+    return new TestCheck(HealthCheckConfig.DEFAULT_CONFIG, "testCheck", testMetricMaker, result);
   }
 
   private static class TestCheck extends AbstractHealthCheck {
     private final Result finalResult;
 
     public TestCheck(
-        HealthCheckConfig config,
-        String name,
-        HealthCheckMetrics.Factory healthCheckMetricsFactory,
-        Result finalResult) {
+        HealthCheckConfig config, String name, MetricMaker metricMaker, Result finalResult) {
       super(
           MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(10)),
           config,
           name,
-          healthCheckMetricsFactory);
+          metricMaker);
       this.finalResult = finalResult;
     }
 
@@ -172,17 +163,4 @@
       return failureCount;
     }
   }
-
-  private static class DummyHealthCheckMetricsFactory implements HealthCheckMetrics.Factory {
-    private final TestMetricMaker metricMaker = new TestMetricMaker();
-
-    @Override
-    public HealthCheckMetrics create(String name) {
-      return new HealthCheckMetrics(metricMaker, name);
-    }
-
-    public TestMetricMaker getMetricMaker() {
-      return metricMaker;
-    }
-  }
 }

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ActiveWorkersCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ActiveWorkersCheckTest.java
index df88c48..8bd3ddd 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ActiveWorkersCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ActiveWorkersCheckTest.java

@@ -21,6 +21,7 @@
 import com.codahale.metrics.Gauge;
 import com.codahale.metrics.MetricRegistry;
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.DisabledMetricMaker;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.ThreadSettingsConfig;
 import com.google.inject.AbstractModule;
@@ -32,7 +33,6 @@
 import org.junit.Test;
 
 public class ActiveWorkersCheckTest {
-  HealthCheckMetrics.Factory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
 
   @Test
   public void shouldPassCheckWhenNoActiveWorkers() {
@@ -105,7 +105,7 @@
   }
 
   private Injector testInjector(AbstractModule testModule) {
-    return Guice.createInjector(new HealthCheckModule(), testModule);
+    return Guice.createInjector(new HealthCheckExtensionApiModule(), testModule);
   }
 
   private MetricRegistry createMetricRegistry(Long value) {
@@ -132,7 +132,7 @@
         healtchCheckConfig,
         injector.getInstance(ThreadSettingsConfig.class),
         injector.getInstance(MetricRegistry.class),
-        healthCheckMetricsFactory);
+        new DisabledMetricMaker());
   }
 
   private class TestModule extends AbstractModule {

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/BlockedThreadsCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/BlockedThreadsCheckTest.java
index c52d646..737b4a7 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/BlockedThreadsCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/BlockedThreadsCheckTest.java

@@ -20,6 +20,8 @@
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
+import com.google.gerrit.metrics.DisabledMetricMaker;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
@@ -213,12 +215,12 @@
   private Injector createTestInjector(HealthCheckConfig config) {
     Injector injector =
         Guice.createInjector(
-            new HealthCheckModule(),
+            new HealthCheckExtensionApiModule(),
             new AbstractModule() {
               @Override
               protected void configure() {
                 bind(HealthCheckConfig.class).toInstance(config);
-                bind(HealthCheckMetrics.Factory.class).to(DummyHealthCheckMetricsFactory.class);
+                bind(MetricMaker.class).toInstance(new DisabledMetricMaker());
                 bind(ThreadBeanProvider.class).toInstance(threadBeanProviderMock);
               }
             },

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DeadlockCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DeadlockCheckTest.java
index aa880a3..a73ca15 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DeadlockCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DeadlockCheckTest.java

@@ -20,6 +20,7 @@
 import com.codahale.metrics.Gauge;
 import com.codahale.metrics.MetricRegistry;
 import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.gerrit.metrics.DisabledMetricMaker;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.ThreadSettingsConfig;
 import com.google.inject.AbstractModule;
@@ -32,8 +33,6 @@
 
 public class DeadlockCheckTest {
 
-  HealthCheckMetrics.Factory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
-
   @Test
   public void shouldPassCheckWhenNoMetric() {
 
@@ -70,7 +69,7 @@
   }
 
   private Injector testInjector(AbstractModule testModule) {
-    return Guice.createInjector(new HealthCheckModule(), testModule);
+    return Guice.createInjector(new HealthCheckExtensionApiModule(), testModule);
   }
 
   private MetricRegistry createMetricRegistry(Integer value) {
@@ -91,7 +90,7 @@
         injector.getInstance(ListeningExecutorService.class),
         DEFAULT_CONFIG,
         injector.getInstance(MetricRegistry.class),
-        healthCheckMetricsFactory);
+        new DisabledMetricMaker());
   }
 
   private class TestModule extends AbstractModule {

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DummyHealthCheckMetricsFactory.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DummyHealthCheckMetricsFactory.java
deleted file mode 100644
index 7523e95..0000000
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/DummyHealthCheckMetricsFactory.java
+++ /dev/null

@@ -1,28 +0,0 @@
-// Copyright (C) 2021 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.googlesource.gerrit.plugins.healthcheck;
-
-import com.google.gerrit.metrics.DisabledMetricMaker;
-import com.google.gerrit.metrics.MetricMaker;
-import org.junit.Ignore;
-
-@Ignore
-public class DummyHealthCheckMetricsFactory implements HealthCheckMetrics.Factory {
-  @Override
-  public HealthCheckMetrics create(String name) {
-    MetricMaker metricMaker = new DisabledMetricMaker();
-    return new HealthCheckMetrics(metricMaker, name);
-  }
-}

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckIT.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckIT.java
index e9901a9..17f1e10 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckIT.java

@@ -29,22 +29,35 @@
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gson.Gson;
 import com.google.gson.JsonObject;
+import com.google.inject.AbstractModule;
 import com.google.inject.Key;
 import com.googlesource.gerrit.plugins.healthcheck.check.HealthCheckNames;
+import java.io.File;
 import java.io.IOException;
+import javax.servlet.http.HttpServletResponse;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.junit.Before;
 import org.junit.Test;
 
 @TestPlugin(
     name = "healthcheck-test",
-    sysModule = "com.googlesource.gerrit.plugins.healthcheck.Module",
+    sysModule = "com.googlesource.gerrit.plugins.healthcheck.HealthCheckIT$TestModule",
     httpModule = "com.googlesource.gerrit.plugins.healthcheck.HttpModule")
 @Sandboxed
 public class HealthCheckIT extends LightweightPluginDaemonTest {
   Gson gson = new Gson();
   HealthCheckConfig config;
   String healthCheckUriPath;
+  String failFilePath;
+
+  public static class TestModule extends AbstractModule {
+
+    @Override
+    protected void configure() {
+      install(new HealthCheckExtensionApiModule());
+      install(new Module());
+    }
+  }
 
   @Override
   @Before
@@ -52,6 +65,9 @@
     super.setUpTestPlugin();
 
     config = plugin.getSysInjector().getInstance(HealthCheckConfig.class);
+    failFilePath = "/tmp/fail";
+    new File(failFilePath).delete();
+
     int numChanges = config.getLimit(HealthCheckNames.QUERYCHANGES);
     for (int i = 0; i < numChanges; i++) {
       createChange("refs/for/master");
@@ -195,6 +211,25 @@
     assertCheckResult(getResponseJson(resp), ACTIVEWORKERS, "passed");
   }
 
+  @Test
+  public void shouldReturnFailedIfFailFlagFileExists() throws Exception {
+    setFailFlagFilePath(failFilePath);
+    createFailFileFlag(failFilePath);
+    getHealthCheckStatus();
+    RestResponse resp = getHealthCheckStatus();
+    resp.assertStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+
+    JsonObject respBody = getResponseJson(resp);
+    assertThat(respBody.has("reason")).isTrue();
+    assertThat(respBody.get("reason").getAsString()).isEqualTo("Fail Flag File exists");
+  }
+
+  private void createFailFileFlag(String path) throws IOException {
+    File file = new File(path);
+    file.createNewFile();
+    file.deleteOnExit();
+  }
+
   private RestResponse getHealthCheckStatus() throws IOException {
     return adminRestSession.get(healthCheckUriPath);
   }
@@ -214,6 +249,10 @@
     config.fromText(String.format("[healthcheck \"%s\"]\n" + "enabled = false", check));
   }
 
+  private void setFailFlagFilePath(String path) throws ConfigInvalidException {
+    config.fromText(String.format("[healthcheck]\n" + "failFileFlagPath = %s", path));
+  }
+
   private JsonObject getResponseJson(RestResponse resp) throws IOException {
     JsonObject respPayload = gson.fromJson(resp.getReader(), JsonObject.class);
     return respPayload;

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckStatusEndpointTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckStatusEndpointTest.java
index b971054..af09d07 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckStatusEndpointTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/HealthCheckStatusEndpointTest.java

@@ -21,6 +21,8 @@
 import com.google.common.util.concurrent.MoreExecutors;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.restapi.Response;
+import com.google.gerrit.metrics.DisabledMetricMaker;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Inject;
@@ -36,7 +38,7 @@
 public class HealthCheckStatusEndpointTest {
 
   @Inject private ListeningExecutorService executor;
-  HealthCheckMetrics.Factory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
+  MetricMaker disabledMetricMaker = new DisabledMetricMaker();
 
   public static class TestHealthCheck extends AbstractHealthCheck {
     private final HealthCheck.Result checkResult;
@@ -47,12 +49,12 @@
         String checkName,
         HealthCheck.Result result,
         long sleep,
-        HealthCheckMetrics.Factory healthCheckMetricsFactory) {
+        MetricMaker metricMaker) {
       super(
           MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(10)),
           config,
           checkName,
-          healthCheckMetricsFactory);
+          metricMaker);
       this.checkResult = result;
       this.sleep = sleep;
     }
@@ -82,12 +84,11 @@
                         "checkOk",
                         HealthCheck.Result.PASSED,
                         0,
-                        healthCheckMetricsFactory);
+                        disabledMetricMaker);
                 DynamicSet<HealthCheck> healthChecks = new DynamicSet<>();
                 healthChecks.add("passingHealthCheck", passingHealthCheck);
                 GlobalHealthCheck globalHealthCheck =
-                    new GlobalHealthCheck(
-                        healthChecks, executor, config, healthCheckMetricsFactory);
+                    new GlobalHealthCheck(healthChecks, executor, config, disabledMetricMaker);
                 bind(GlobalHealthCheck.class).toInstance(globalHealthCheck);
                 bind(HealthCheckConfig.class).toInstance(config);
               }
@@ -111,16 +112,11 @@
                     new HealthCheckConfig("[healthcheck]\n" + "timeout = 20");
                 TestHealthCheck testHealthCheck =
                     new TestHealthCheck(
-                        config,
-                        "checkOk",
-                        HealthCheck.Result.PASSED,
-                        30,
-                        healthCheckMetricsFactory);
+                        config, "checkOk", HealthCheck.Result.PASSED, 30, disabledMetricMaker);
                 DynamicSet<HealthCheck> healthChecks = new DynamicSet<>();
                 healthChecks.add("testHealthCheck", testHealthCheck);
                 GlobalHealthCheck globalHealthCheck =
-                    new GlobalHealthCheck(
-                        healthChecks, executor, config, healthCheckMetricsFactory);
+                    new GlobalHealthCheck(healthChecks, executor, config, disabledMetricMaker);
                 bind(GlobalHealthCheck.class).toInstance(globalHealthCheck);
                 bind(HealthCheckConfig.class).toInstance(config);
               }
@@ -148,7 +144,7 @@
                         "checkOk",
                         HealthCheck.Result.PASSED,
                         0,
-                        healthCheckMetricsFactory);
+                        disabledMetricMaker);
 
                 TestHealthCheck failingHealthCheck =
                     new TestHealthCheck(
@@ -156,14 +152,13 @@
                         "checkKo",
                         HealthCheck.Result.FAILED,
                         0,
-                        healthCheckMetricsFactory);
+                        disabledMetricMaker);
 
                 DynamicSet<HealthCheck> healthChecks = new DynamicSet<>();
                 healthChecks.add("passingHealthCheck", passingHealthCheck);
                 healthChecks.add("failingHealthCheck", failingHealthCheck);
                 GlobalHealthCheck globalHealthCheck =
-                    new GlobalHealthCheck(
-                        healthChecks, executor, config, healthCheckMetricsFactory);
+                    new GlobalHealthCheck(healthChecks, executor, config, disabledMetricMaker);
                 bind(GlobalHealthCheck.class).toInstance(globalHealthCheck);
                 bind(HealthCheckConfig.class).toInstance(config);
               }
@@ -177,6 +172,7 @@
   }
 
   private Injector testInjector(AbstractModule testModule) {
-    return Guice.createInjector(new HealthCheckModule(), new HealthCheckApiModule(), testModule);
+    return Guice.createInjector(
+        new HealthCheckExtensionApiModule(), new HealthCheckApiModule(), testModule);
   }
 }

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/JGitHealthCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/JGitHealthCheckTest.java
index b589dcc..02b914c 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/JGitHealthCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/JGitHealthCheckTest.java

@@ -22,6 +22,8 @@
 
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.metrics.DisabledMetricMaker;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.config.AllProjectsName;
 import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.git.GitRepositoryManager;
@@ -53,11 +55,11 @@
 
   @Inject private ListeningExecutorService executor;
 
-  HealthCheckMetrics.Factory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
+  MetricMaker disabledMetricMaker = new DisabledMetricMaker();
 
   @Before
   public void setupAllProjects() throws Exception {
-    Guice.createInjector(new HealthCheckModule()).injectMembers(this);
+    Guice.createInjector(new HealthCheckExtensionApiModule()).injectMembers(this);
 
     InMemoryRepositoryManager.Repo allProjects =
         inMemoryRepositoryManager.createRepository(allProjectsName);
@@ -72,7 +74,7 @@
   public void shouldBeHealthyWhenJGitIsWorking() {
     JGitHealthCheck check =
         new JGitHealthCheck(
-            executor, DEFAULT_CONFIG, getWorkingRepositoryManager(), healthCheckMetricsFactory);
+            executor, DEFAULT_CONFIG, getWorkingRepositoryManager(), disabledMetricMaker);
     assertThat(check.run().result).isEqualTo(Result.PASSED);
   }
 
@@ -80,7 +82,7 @@
   public void shouldBeUnhealthyWhenJGitIsFailingForAllRepos() {
     JGitHealthCheck jGitHealthCheck =
         new JGitHealthCheck(
-            executor, DEFAULT_CONFIG, getFailingGitRepositoryManager(), healthCheckMetricsFactory);
+            executor, DEFAULT_CONFIG, getFailingGitRepositoryManager(), disabledMetricMaker);
     assertThat(jGitHealthCheck.run().result).isEqualTo(Result.FAILED);
   }
 
@@ -94,8 +96,7 @@
                 + "  project = All-Users\n"
                 + "  project = Not-Existing-Repo");
     JGitHealthCheck jGitHealthCheck =
-        new JGitHealthCheck(
-            executor, config, getWorkingRepositoryManager(), healthCheckMetricsFactory);
+        new JGitHealthCheck(executor, config, getWorkingRepositoryManager(), disabledMetricMaker);
     assertThat(jGitHealthCheck.run().result).isEqualTo(Result.FAILED);
   }
 

diff --git a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ProjectsListHealthCheckTest.java b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ProjectsListHealthCheckTest.java
index 7cbd799..610284c 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ProjectsListHealthCheckTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/healthcheck/ProjectsListHealthCheckTest.java

@@ -20,6 +20,8 @@
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.extensions.common.ProjectInfo;
 import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.metrics.DisabledMetricMaker;
+import com.google.gerrit.metrics.MetricMaker;
 import com.google.gerrit.server.restapi.project.ListProjects;
 import com.google.gerrit.server.restapi.project.ListProjectsImpl;
 import com.google.gerrit.server.util.OneOffRequestContext;
@@ -42,7 +44,7 @@
 public class ProjectsListHealthCheckTest {
   @Inject private ListeningExecutorService executor;
 
-  HealthCheckMetrics.Factory healthCheckMetricsFactory = new DummyHealthCheckMetricsFactory();
+  MetricMaker disabledMetricMaker = new DisabledMetricMaker();
 
   private Config gerritConfig = new Config();
 
@@ -50,18 +52,14 @@
 
   @Before
   public void setUp() throws Exception {
-    Guice.createInjector(new HealthCheckModule()).injectMembers(this);
+    Guice.createInjector(new HealthCheckExtensionApiModule()).injectMembers(this);
   }
 
   @Test
   public void shouldBeHealthyWhenListProjectsWorks() {
     ProjectsListHealthCheck jGitHealthCheck =
         new ProjectsListHealthCheck(
-            executor,
-            DEFAULT_CONFIG,
-            getWorkingProjectList(0),
-            mockOneOffCtx,
-            healthCheckMetricsFactory);
+            executor, DEFAULT_CONFIG, getWorkingProjectList(0), mockOneOffCtx, disabledMetricMaker);
     assertThat(jGitHealthCheck.run().result).isEqualTo(Result.PASSED);
   }
 
@@ -69,11 +67,7 @@
   public void shouldBeUnhealthyWhenListProjectsIsFailing() {
     ProjectsListHealthCheck jGitHealthCheck =
         new ProjectsListHealthCheck(
-            executor,
-            DEFAULT_CONFIG,
-            getFailingProjectList(),
-            mockOneOffCtx,
-            healthCheckMetricsFactory);
+            executor, DEFAULT_CONFIG, getFailingProjectList(), mockOneOffCtx, disabledMetricMaker);
     assertThat(jGitHealthCheck.run().result).isEqualTo(Result.FAILED);
   }
 
@@ -85,14 +79,13 @@
             DEFAULT_CONFIG,
             getWorkingProjectList(DEFAULT_CONFIG.getTimeout() * 2),
             mockOneOffCtx,
-            healthCheckMetricsFactory);
+            disabledMetricMaker);
     assertThat(jGitHealthCheck.run().result).isEqualTo(Result.TIMEOUT);
   }
 
   private Provider<ListProjects> getFailingProjectList() {
     return Providers.of(
-        new ListProjectsImpl(
-            null, null, null, null, null, null, null, null, null, gerritConfig, null) {
+        new ListProjectsImpl(null, null, null, null, null, null, null, null, null, gerritConfig, null) {
 
           @Override
           public SortedMap<String, ProjectInfo> apply() throws BadRequestException {
@@ -103,8 +96,7 @@
 
   private Provider<ListProjects> getWorkingProjectList(long execTime) {
     return Providers.of(
-        new ListProjectsImpl(
-            null, null, null, null, null, null, null, null, null, gerritConfig, null) {
+        new ListProjectsImpl(null, null, null, null, null, null, null, null, null, gerritConfig, null) {
 
           @Override
           public SortedMap<String, ProjectInfo> apply() throws BadRequestException {