diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
index 8edb479..6da211c 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Action.java
@@ -16,10 +16,8 @@
 
 import static java.util.stream.Collectors.toList;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Streams;
 import com.google.common.flogger.FluentLogger;
-import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestReadView;
@@ -54,12 +52,14 @@
 class Action implements RestReadView<RevisionResource>, UiAction<RevisionResource> {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  private AccountCache accountCache;
-  private Emails emails;
-  private ChangeData.Factory changeDataFactory;
-  private GitRepositoryManager repoManager;
-  private Provider<CurrentUser> userProvider;
-  private ProjectCache projectCache;
+  private final AccountCache accountCache;
+  private final Emails emails;
+  private final ChangeData.Factory changeDataFactory;
+  private final GitRepositoryManager repoManager;
+  private final PluginConfigFactory configFactory;
+  private final Provider<CurrentUser> userProvider;
+  private final ProjectCache projectCache;
+  private final Config config;
 
   static class Parameters {
     Boolean debug; // REST API "debug" parameter, or null
@@ -69,7 +69,6 @@
 
   @Inject
   Action(
-      @PluginName String pluginName,
       PluginConfigFactory configFactory,
       Provider<CurrentUser> userProvider,
       ChangeData.Factory changeDataFactory,
@@ -83,13 +82,10 @@
     this.emails = emails;
     this.repoManager = repoManager;
     this.projectCache = projectCache;
-    Config.setVariables(pluginName, configFactory);
-    Cache.getInstance(); // Create a single Cache.
+    this.configFactory = configFactory;
+    this.config = new Config(configFactory);
   }
 
-  @VisibleForTesting
-  Action() {}
-
   private String getUserName() {
     if (userProvider != null && userProvider.get().getUserName().isPresent()) {
       return userProvider.get().getUserName().get();
@@ -166,14 +162,14 @@
     int patchset = getValidPatchsetNum(changeData, params.patchset);
     ProjectState projectState = projectCache.get(changeData.project());
     Boolean useCache = params.nocache == null || !params.nocache;
-    OwnersDb db = Cache.getInstance().get(
-        useCache, projectState, accountCache, emails, repoManager, changeData, patchset);
+    OwnersDb db = Cache.getInstance(configFactory, repoManager).get(
+        useCache, projectState, accountCache, emails, repoManager, configFactory, changeData, patchset);
     Collection<String> changedFiles = changeData.currentFilePaths();
     Map<String, Set<String>> file2Owners = db.findOwners(changedFiles);
 
-    Boolean addDebugMsg = (params.debug != null) ? params.debug : Config.getAddDebugMsg();
+    Boolean addDebugMsg = (params.debug != null) ? params.debug : config.getAddDebugMsg();
     RestResult obj =
-        new RestResult(Config.getMinOwnerVoteLevel(projectState, changeData), addDebugMsg);
+        new RestResult(config.getMinOwnerVoteLevel(projectState, changeData), addDebugMsg);
     obj.change = changeData.getId().get();
     obj.patchset = patchset;
     obj.ownerRevision = db.revision;
@@ -214,16 +210,17 @@
               && status != Status.ABANDONED
               && status != Status.MERGED;
       // If alwaysShowButton is true, skip expensive owner lookup.
-      if (needFindOwners && !Config.getAlwaysShowButton()) {
+      if (needFindOwners && !config.getAlwaysShowButton()) {
         needFindOwners = false; // Show button only if some owner is found.
         OwnersDb db =
-            Cache.getInstance()
+            Cache.getInstance(configFactory, repoManager)
                 .get(
                     true, // use cached OwnersDb
                     projectCache.get(resource.getProject()),
                     accountCache,
                     emails,
                     repoManager,
+                    configFactory,
                     changeData);
         logger.atFiner().log("getDescription db key = %s", db.key);
         needFindOwners = db.getNumOwners() > 0;
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
index df56fc7..072c087 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Cache.java
@@ -20,12 +20,16 @@
 import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.Emails;
+import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.OrmException;
 import java.io.IOException;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.WeakHashMap;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 
@@ -48,18 +52,17 @@
   // It would not be enough to keep the cache in a Prolog engine environment
   // or a StoredValues.
 
-  private static Cache instance = null; // a singleton
+  // Since a Java runtime can host multiple Gerrit sites, each site should have
+  // its own cache. We assume that each site has its own GitRepositoryManager.
+  // We use a WeakHashMap to avoid leaking objects in the map.
+  private static final Map<GitRepositoryManager, Cache> cacheMap =
+      Collections.synchronizedMap(new WeakHashMap<GitRepositoryManager, Cache>());
 
-  // When branch is "refs/heads/xyz" use only "xyz",
-  // to share cached OwnersDb between these two branch names.
-  private static final String REFS_HEADS = "refs/heads/";
-
-  // Until we have a way to inject Java singleton into Prolog PRED_* constructors,
-  // we keep the cache in a static object for all HTTP requests.
+  // dbCache key is generated by makeKey.
   private com.google.common.cache.Cache<String, OwnersDb> dbCache;
 
-  private Cache() {
-    init(Config.getMaxCacheAge(), Config.getMaxCacheSize());
+  private Cache(int maxSeconds, int maxSize) {
+    init(maxSeconds, maxSize);
   }
 
   long size() {
@@ -93,6 +96,7 @@
       AccountCache accountCache,
       Emails emails,
       GitRepositoryManager repoManager,
+      PluginConfigFactory configFactory,
       ChangeData changeData)
       throws OrmException, IOException {
     return get(
@@ -101,6 +105,7 @@
         accountCache,
         emails,
         repoManager,
+        configFactory,
         changeData,
         changeData.currentPatchSet().getId().get());
   }
@@ -112,11 +117,12 @@
       AccountCache accountCache,
       Emails emails,
       GitRepositoryManager repoManager,
+      PluginConfigFactory configFactory,
       ChangeData changeData,
       int patchset)
       throws OrmException, IOException {
     String branch = changeData.change().getDest().get();
-    String dbKey = Cache.makeKey(changeData.getId().get(), patchset, branch);
+    String dbKey = Cache.makeKey(changeData.getId().get(), patchset, repoManager);
     // TODO: get changed files of the given patchset?
     return get(
         useCache,
@@ -125,6 +131,7 @@
         emails,
         dbKey,
         repoManager,
+        configFactory,
         changeData,
         branch,
         changeData.currentFilePaths());
@@ -138,13 +145,22 @@
       Emails emails,
       String key,
       GitRepositoryManager repoManager,
+      PluginConfigFactory configFactory,
       ChangeData changeData,
       String branch,
       Collection<String> files) {
     if (dbCache == null || !useCache) { // Do not cache OwnersDb
       logger.atFiner().log("Create new OwnersDb, key=%s", key);
       return new OwnersDb(
-          projectState, accountCache, emails, key, repoManager, changeData, branch, files);
+          projectState,
+          accountCache,
+          emails,
+          key,
+          repoManager,
+          configFactory,
+          changeData,
+          branch,
+          files);
     }
     try {
       logger.atFiner().log(
@@ -156,28 +172,45 @@
             public OwnersDb call() {
               logger.atFiner().log("Create new OwnersDb, key=%s", key);
               return new OwnersDb(
-                  projectState, accountCache, emails, key, repoManager, changeData, branch, files);
+                  projectState,
+                  accountCache,
+                  emails,
+                  key,
+                  repoManager,
+                  configFactory,
+                  changeData,
+                  branch,
+                  files);
             }
           });
     } catch (ExecutionException e) {
       logger.atSevere().withCause(e).log(
           "Cache.get has exception for %s", Config.getChangeId(changeData));
       return new OwnersDb(
-          projectState, accountCache, emails, key, repoManager, changeData, branch, files);
+          projectState,
+          accountCache,
+          emails,
+          key,
+          repoManager,
+          configFactory,
+          changeData,
+          branch,
+          files);
     }
   }
 
-  public static String makeKey(int change, int patch, String branch) {
-    if (branch.indexOf(REFS_HEADS) == 0) {
-      branch = branch.substring(REFS_HEADS.length());
-    }
-    return change + ":" + patch + ":" + branch;
+  public static String makeKey(int change, int patch, GitRepositoryManager repoManager) {
+    return String.format("%d:%d:%H", change, patch, repoManager);
   }
 
-  public static Cache getInstance() {
-    if (instance == null) {
-      instance = new Cache();
+  public static Cache getInstance(
+      PluginConfigFactory configFactory, GitRepositoryManager repoManager) {
+    Cache cache = cacheMap.get(repoManager);
+    if (cache == null) {
+      Config config = new Config(configFactory);
+      cache = new Cache(config.getMaxCacheAge(), config.getMaxCacheSize());
+      cacheMap.put(repoManager, cache);
     }
-    return instance;
+    return cache;
   }
 }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
index 187e87b..7b7540b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Checker.java
@@ -19,6 +19,7 @@
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.Emails;
+import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -40,12 +41,19 @@
   private static final String EXEMPT_MESSAGE2 = "Exempted-From-Owner-Approval:";
 
   private final GitRepositoryManager repoManager;
+  private final PluginConfigFactory configFactory;
+  private final Config config;
+  private final ProjectState projectState; // could be null when used by FindOwnersIT
   private final ChangeData changeData;
   private int minVoteLevel;
 
-  Checker(GitRepositoryManager repoManager, ChangeData changeData, int v) {
+  Checker(GitRepositoryManager repoManager, PluginConfigFactory configFactory,
+          ProjectState projectState, ChangeData changeData, int v) {
     this.repoManager = repoManager;
+    this.configFactory = configFactory;
+    this.projectState = projectState;
     this.changeData = changeData;
+    this.config = new Config(configFactory);
     minVoteLevel = v;
   }
 
@@ -97,7 +105,7 @@
   /** Returns 1 if owner approval is found, -1 if missing, 0 if unneeded. */
   int findApproval(AccountCache accountCache, OwnersDb db) throws OrmException, IOException {
     Map<String, Set<String>> file2Owners = db.findOwners(changeData.currentFilePaths());
-    if (file2Owners.size() == 0) { // do not need owner approval
+    if (file2Owners.isEmpty()) { // do not need owner approval
       return 0;
     }
     Map<String, Integer> votes = getVotes(accountCache, changeData);
@@ -114,18 +122,41 @@
     ChangeData changeData = null;
     try {
       changeData = StoredValues.CHANGE_DATA.get(engine);
-      ProjectState projectState = StoredValues.PROJECT_STATE.get(engine);
-      GitRepositoryManager repoManager = StoredValues.REPO_MANAGER.get(engine);
-      AccountCache accountCache = StoredValues.ACCOUNT_CACHE.get(engine);
-      Emails emails = StoredValues.EMAILS.get(engine);
-      return new Checker(repoManager, changeData, minVoteLevel)
-          .findApproval(projectState, accountCache, emails);
+      Checker checker = new Checker(
+          StoredValues.REPO_MANAGER.get(engine),
+          StoredValues.PLUGIN_CONFIG_FACTORY.get(engine),
+          StoredValues.PROJECT_STATE.get(engine),
+          changeData, minVoteLevel);
+      return checker.findApproval(
+          StoredValues.ACCOUNT_CACHE.get(engine),
+          StoredValues.EMAILS.get(engine));
     } catch (OrmException | IOException e) {
       logger.atSevere().withCause(e).log("Exception for %s ", Config.getChangeId(changeData));
       return 0; // owner approval may or may not be required.
     }
   }
 
+  /** Returns 1 if owner approval is found, -1 if missing, 0 if unneeded. */
+  int findApproval(AccountCache accountCache, Emails emails)
+      throws OrmException, IOException {
+    if (isExemptFromOwnerApproval(changeData)) {
+      return 0;
+    }
+    // One update to a Gerrit change can call submit_rule or submit_filter
+    // many times. So this function should use cached values.
+    OwnersDb db =
+        Cache.getInstance(configFactory, repoManager)
+            .get(true, projectState, accountCache, emails, repoManager, configFactory, changeData);
+    if (db.getNumOwners() <= 0) {
+      return 0;
+    }
+    if (minVoteLevel <= 0) {
+      minVoteLevel = config.getMinOwnerVoteLevel(projectState, changeData);
+    }
+    logger.atFiner().log("findApproval db key = %s", db.key);
+    return findApproval(accountCache, db);
+  }
+
   /** Returns true if exempt from owner approval. */
   static boolean isExemptFromOwnerApproval(ChangeData changeData) throws OrmException {
     try {
@@ -142,23 +173,4 @@
     Status status = changeData.change().getStatus();
     return (status == Status.ABANDONED || status == Status.MERGED);
   }
-
-  int findApproval(ProjectState projectState, AccountCache accountCache, Emails emails)
-      throws OrmException, IOException {
-    if (isExemptFromOwnerApproval(changeData)) {
-      return 0;
-    }
-    // One update to a Gerrit change can call submit_rule or submit_filter
-    // many times. So this function should use cached values.
-    OwnersDb db =
-        Cache.getInstance().get(true, projectState, accountCache, emails, repoManager, changeData);
-    if (db.getNumOwners() <= 0) {
-      return 0;
-    }
-    if (minVoteLevel <= 0) {
-      minVoteLevel = Config.getMinOwnerVoteLevel(projectState, changeData);
-    }
-    logger.atFiner().log("findApproval db key = %s", db.key);
-    return findApproval(accountCache, db);
-  }
 }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
index 20b5d11..0653f3f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/Config.java
@@ -38,23 +38,25 @@
   static final String PLUGIN_NAME = "find-owners";
   static final String PROLOG_NAMESPACE = "find_owners";
 
+  private final PluginConfigFactory configFactory;
+
   // Global/plugin config parameters.
-  private static PluginConfigFactory config = null;
-  private static boolean addDebugMsg = false;
-  private static int minOwnerVoteLevel = 1;
-  private static int maxCacheAge = 0;
-  private static int maxCacheSize = 1000;
-  private static boolean reportSyntaxError = false;
-  private static boolean alwaysShowButton = false;
+  private boolean addDebugMsg = false;
+  private int minOwnerVoteLevel = 1;
+  private int maxCacheAge = 0;
+  private int maxCacheSize = 1000;
+  private boolean reportSyntaxError = false;
+  private boolean alwaysShowButton = false;
+  private String ownersFileName = OWNERS;
 
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  static void setVariables(String pluginName, PluginConfigFactory conf) {
-    if (conf == null) { // When called from integration tests.
+  Config(PluginConfigFactory configFactory) {
+    this.configFactory = configFactory;
+    if (configFactory == null) { // When called from integration tests.
       return;
     }
-    config = conf;
-    PluginConfig gc = config.getFromGerritConfig(pluginName, true);
+    PluginConfig gc = configFactory.getFromGerritConfig(PLUGIN_NAME);
     // Get config variables from the plugin section of gerrit.config
     addDebugMsg = gc.getBoolean(ADD_DEBUG_MSG, false);
     reportSyntaxError = gc.getBoolean(REPORT_SYNTAX_ERROR, false);
@@ -62,25 +64,26 @@
     minOwnerVoteLevel = gc.getInt(MIN_OWNER_VOTE_LEVEL, 1);
     maxCacheAge = gc.getInt(MAX_CACHE_AGE, 0);
     maxCacheSize = gc.getInt(MAX_CACHE_SIZE, 1000);
+    ownersFileName = gc.getString(OWNERS_FILE_NAME, OWNERS);
   }
 
-  static boolean getAddDebugMsg() {
+  boolean getAddDebugMsg() {
     return addDebugMsg; // defined globally, not per-project
   }
 
-  static int getMaxCacheAge() {
+  int getMaxCacheAge() {
     return maxCacheAge;
   }
 
-  static int getMaxCacheSize() {
+  int getMaxCacheSize() {
     return maxCacheSize;
   }
 
-  static boolean getReportSyntaxError() {
+  boolean getReportSyntaxError() {
     return reportSyntaxError;
   }
 
-  static boolean getAlwaysShowButton() {
+  boolean getAlwaysShowButton() {
     return alwaysShowButton;
   }
 
@@ -88,43 +91,39 @@
     return data == null ? "(unknown change)" : ("change c/" + data.getId().get());
   }
 
-  static String getDefaultOwnersFileName() {
-    return OWNERS;
+  String getDefaultOwnersFileName() {
+    return ownersFileName; // could be defined in gerrit.config
   }
 
-  static String getOwnersFileName(ProjectState projectState, ChangeData c) {
+  private PluginConfig getPluginConfig(ProjectState state) {
+    return configFactory.getFromProjectConfigWithInheritance(state, PLUGIN_NAME);
+  }
+
+  String getOwnersFileName(ProjectState projectState, ChangeData c) {
+    String defaultName = getDefaultOwnersFileName();
     if (projectState == null) {
       logger.atSevere().log("Null projectState for change %s", getChangeId(c));
-    } else if (config != null) {
-      String name =
-          config
-              .getFromProjectConfigWithInheritance(projectState, PLUGIN_NAME)
-              .getString(OWNERS_FILE_NAME, OWNERS);
-      if (name.trim().equals("")) {
-        logger.atSevere().log("Project %s has wrong %s: \"%s\" for %s",
-            projectState.getProject(), OWNERS_FILE_NAME, name, getChangeId(c));
-        return OWNERS;
-      }
-      return name;
+      return defaultName;
     }
-    return OWNERS;
+    String name = getPluginConfig(projectState).getString(OWNERS_FILE_NAME, defaultName);
+    if (name.trim().isEmpty()) {
+      logger.atSevere().log("Project %s has wrong %s: \"%s\" for %s",
+          projectState.getProject(), OWNERS_FILE_NAME, name, getChangeId(c));
+      return defaultName;
+    }
+    return name;
   }
 
   @VisibleForTesting
-  static void setReportSyntaxError(boolean value) {
+  void setReportSyntaxError(boolean value) {
     reportSyntaxError = value;
   }
 
-  static int getMinOwnerVoteLevel(ProjectState projectState, ChangeData c) {
+  int getMinOwnerVoteLevel(ProjectState projectState, ChangeData c) {
     if (projectState == null) {
       logger.atSevere().log("Null projectState for change %s", getChangeId(c));
       return minOwnerVoteLevel;
-    } else if (config == null) {
-      return minOwnerVoteLevel;
-    } else {
-      return config
-          .getFromProjectConfigWithInheritance(projectState, PLUGIN_NAME)
-          .getInt(MIN_OWNER_VOTE_LEVEL, minOwnerVoteLevel);
     }
+    return getPluginConfig(projectState).getInt(MIN_OWNER_VOTE_LEVEL, minOwnerVoteLevel);
   }
 }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/GetOwners.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/GetOwners.java
index f1b2303..f08056d 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/GetOwners.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/GetOwners.java
@@ -15,7 +15,6 @@
 package com.googlesource.gerrit.plugins.findowners;
 
 import com.google.common.flogger.FluentLogger;
-import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestReadView;
@@ -53,7 +52,6 @@
 
   @Inject
   GetOwners(
-      @PluginName String pluginName,
       PluginConfigFactory configFactory,
       Provider<CurrentUser> userProvider,
       ChangeData.Factory dataFactory,
@@ -63,7 +61,6 @@
       ProjectCache projectCache) {
     this.action =
         new Action(
-            pluginName,
             configFactory,
             userProvider,
             dataFactory,
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
index 23cc28a..41b97cd 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/OwnersDb.java
@@ -22,6 +22,7 @@
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.Emails;
+import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -50,9 +51,10 @@
 class OwnersDb {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  private AccountCache accountCache;
-  private GitRepositoryManager repoManager;
-  private Emails emails;
+  private final AccountCache accountCache;
+  private final GitRepositoryManager repoManager;
+  private final Emails emails;
+  private final Config config;
   private int numOwners = -1; // # of owners of all given files.
 
   String key = ""; // key to find this OwnersDb in a cache.
@@ -66,14 +68,13 @@
   List<String> errors = new ArrayList<>(); // error messages
   List<String> logs = new ArrayList<>(); // trace/debug messages
 
-  OwnersDb() {}
-
   OwnersDb(
       ProjectState projectState,
       AccountCache accountCache,
       Emails emails,
       String key,
       GitRepositoryManager repoManager,
+      PluginConfigFactory configFactory,
       ChangeData changeData,
       String branch,
       Collection<String> files) {
@@ -81,6 +82,7 @@
     this.repoManager = repoManager;
     this.emails = emails;
     this.key = key;
+    this.config = new Config(configFactory);
     try {
       InetAddress inetAddress = InetAddress.getLocalHost();
       logs.add("HostName:" + inetAddress.getHostName());
@@ -91,7 +93,7 @@
     preferredEmails.put("*", "*");
     String projectName = projectState.getName();
     logs.add("project:" + projectName);
-    String ownersFileName = Config.getOwnersFileName(projectState, changeData);
+    String ownersFileName = config.getOwnersFileName(projectState, changeData);
     logs.add("ownersFileName:" + ownersFileName);
     try (Repository repo = repoManager.openRepository(projectState.getNameKey())) {
       // Some hacked CL could have a target branch that is not created yet.
@@ -151,7 +153,7 @@
   }
 
   int getNumOwners() {
-    return (numOwners >= 0) ? numOwners : owner2Paths.keySet().size();
+    return (numOwners >= 0) ? numOwners : owner2Paths.size();
   }
 
   private void countNumOwners(Collection<String> files) {
@@ -162,7 +164,7 @@
       file2Owners.values().forEach(emails::addAll);
       numOwners = emails.size();
     } else {
-      numOwners = owner2Paths.keySet().size();
+      numOwners = owner2Paths.size();
     }
   }
 
@@ -227,7 +229,7 @@
         addOwnerPathPair(email, path);
       }
     }
-    if (Config.getReportSyntaxError()) {
+    if (config.getReportSyntaxError()) {
       result.warnings.forEach(w -> logger.atWarning().log(w));
       result.errors.forEach(w -> logger.atSevere().log(w));
     }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/findowners/PredicateModule.java b/src/main/java/com/googlesource/gerrit/plugins/findowners/PredicateModule.java
index d0fb040..6a2e28d 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/findowners/PredicateModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/findowners/PredicateModule.java
@@ -15,24 +15,15 @@
 package com.googlesource.gerrit.plugins.findowners;
 
 import com.google.common.collect.ImmutableSet;
-import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.gerrit.server.rules.PredicateProvider;
 import com.google.inject.AbstractModule;
-import com.google.inject.Inject;
 
 /** provides the Prolog predicate, even in a batch mode */
 public class PredicateModule extends AbstractModule {
   /** Prolog Predicate Provider. */
   static class FindOwnersProvider implements PredicateProvider {
 
-    @Inject
-    public FindOwnersProvider(@PluginName String pluginName, PluginConfigFactory configFactory) {
-      Config.setVariables(pluginName, configFactory);
-      Cache.getInstance(); // Create a single Cache.
-    }
-
     @Override
     public ImmutableSet<String> getPackages() {
       return ImmutableSet.of(Config.PROLOG_NAMESPACE);
diff --git a/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java b/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
index 0ef3b3e..7559da9 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/findowners/FindOwnersIT.java
@@ -39,7 +39,6 @@
 import com.google.gerrit.server.account.AccountState;
 import com.google.gerrit.server.account.Emails;
 import com.google.gerrit.server.change.ChangeResource;
-import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.inject.Inject;
 import java.util.Collection;
 import java.util.Optional;
@@ -50,6 +49,7 @@
 import org.eclipse.jgit.transport.RefSpec;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.filter.PathFilterGroup;
+import org.junit.Before;
 import org.junit.Test;
 
 /** Test find-owners plugin API. */
@@ -57,8 +57,13 @@
 public class FindOwnersIT extends LightweightPluginDaemonTest {
 
   @Inject private Emails emails;
-  @Inject private PluginConfigFactory configFactory;
   @Inject private ProjectOperations projectOperations;
+  private Config config;
+
+  @Before
+  public void setConfig() {
+    config = new Config(pluginConfig);
+  }
 
   @Test
   public void getOwnersTest() throws Exception {
@@ -564,7 +569,7 @@
 
     // Default owners file name is "OWNERS".
     assertThat(Config.OWNERS).isEqualTo("OWNERS");
-    assertThat(Config.getDefaultOwnersFileName()).isEqualTo("OWNERS");
+    assertThat(config.getDefaultOwnersFileName()).isEqualTo("OWNERS");
     assertThat(projectOwnersFileName(pA)).isEqualTo("OWNERS");
     assertThat(projectOwnersFileName(pB)).isEqualTo("OWNERS");
 
@@ -697,8 +702,7 @@
     Action.Parameters param = new Action.Parameters();
     Action action =
         new Action(
-            Config.PLUGIN_NAME,
-            configFactory,
+            pluginConfig,
             null,
             changeDataFactory,
             accountCache,
@@ -828,8 +832,8 @@
     Project.NameKey project = r.getChange().project();
     Cache cache = getCache().init(0, 0);
     OwnersDb db = cache.get(true, projectCache.get(project), accountCache, emails,
-                            repoManager, r.getChange(), 1);
-    Checker c = new Checker(repoManager, r.getChange(), 1);
+                            repoManager, pluginConfig, r.getChange(), 1);
+    Checker c = new Checker(repoManager, pluginConfig, null, r.getChange(), 1);
     return c.findApproval(accountCache, db);
   }
 
@@ -889,10 +893,10 @@
   }
 
   private String projectOwnersFileName(Project.NameKey name) {
-    return Config.getOwnersFileName(projectCache.get(name), null);
+    return config.getOwnersFileName(projectCache.get(name), null);
   }
 
   private Cache getCache() {
-    return Cache.getInstance();
+    return Cache.getInstance(pluginConfig, repoManager);
   }
 }