Allow to enable/disable push/pull replication filters The multi-site plugin had always enabled all replication filtering with the checking of their global-refdb status. Although it is a good default to have, the lack of flexibility brought some additional performance issues when running unneeded checks of hundreds of thousands of refs against the global-refdb. Example: the replication endpoint is not Gerrit or is a Gerrit replica, therefore there is no need to integrate and check with the global-refdb consistency, because the endpoint won't be tracked under it anyway. On Cloud environments where the global-refdb is provided as a service, the consumption of the APIs is very expensive and can also be capped or rate-limited, causing potential outages due to unneeded calls. Introduce two new settings for enabling/disabling the filtering individually for the push or pull-replication plugins. Example: [ref-database] pushReplicationFilterClassEnabled = false Change-Id: I1989f3bbc8c257f9bb5847e7d3c7755464e2cf3a

diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/Configuration.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/Configuration.java
index a7a05d3..dd694f6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/Configuration.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/Configuration.java

@@ -58,6 +58,8 @@
   private static final String REPLICATION_LAG_REFRESH_INTERVAL = "replicationLagRefreshInterval";
   private static final String REPLICATION_LAG_ENABLED = "replicationLagEnabled";
   private static final Duration REPLICATION_LAG_REFRESH_INTERVAL_DEFAULT = Duration.ofSeconds(60);
+  private static final String PUSH_REPLICATION_FILTER_ENABLED = "pushReplicationFilterEnabled";
+  private static final String PULL_REPLICATION_FILTER_ENABLED = "pullReplicationFilterEnabled";
 
   private static final String REPLICATION_CONFIG = "replication.config";
   // common parameters to cache and index sections
@@ -79,6 +81,8 @@
   private final Config multiSiteConfig;
   private final Supplier<Duration> replicationLagRefreshInterval;
   private final Supplier<Boolean> replicationLagEnabled;
+  private final Supplier<Boolean> pushReplicationFilterEnabled;
+  private final Supplier<Boolean> pullReplicationFilterEnabled;
 
   @Inject
   Configuration(SitePaths sitePaths) {
@@ -118,6 +122,19 @@
                 lazyMultiSiteCfg
                     .get()
                     .getBoolean(REF_DATABASE, null, REPLICATION_LAG_ENABLED, true));
+
+    pushReplicationFilterEnabled =
+        memoize(
+            () ->
+                lazyMultiSiteCfg
+                    .get()
+                    .getBoolean(REF_DATABASE, null, PUSH_REPLICATION_FILTER_ENABLED, true));
+    pullReplicationFilterEnabled =
+        memoize(
+            () ->
+                lazyMultiSiteCfg
+                    .get()
+                    .getBoolean(REF_DATABASE, null, PULL_REPLICATION_FILTER_ENABLED, true));
   }
 
   public Config getMultiSiteConfig() {
@@ -160,6 +177,14 @@
     return replicationLagEnabled.get();
   }
 
+  public boolean pushReplicationFilterEnabled() {
+    return pushReplicationFilterEnabled.get();
+  }
+
+  public boolean pullRepllicationFilterEnabled() {
+    return pullReplicationFilterEnabled.get();
+  }
+
   public Collection<Message> validate() {
     return replicationConfigValidation.get();
   }

diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/PluginModule.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/PluginModule.java
index db06c9f..3ced8c6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/PluginModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/PluginModule.java

@@ -35,14 +35,10 @@
 
 public class PluginModule extends LifecycleModule {
   private static final FluentLogger log = FluentLogger.forEnclosingClass();
-  private static final String[] FILTER_MODULES_CLASS_NAMES =
-      new String[] {
-        /* Class names are defined as String for avoiding this class failing to load
-         * if either replication or pull-replication plugins are missing.
-         */
-        "com.googlesource.gerrit.plugins.multisite.validation.PullReplicationFilterModule",
-        "com.googlesource.gerrit.plugins.multisite.validation.PushReplicationFilterModule"
-      };
+  public static final String PULL_REPLICATION_FILTER_MODULE =
+      "com.googlesource.gerrit.plugins.multisite.validation.PullReplicationFilterModule";
+  public static final String PUSH_REPLICATION_FILTER_MODULE =
+      "com.googlesource.gerrit.plugins.multisite.validation.PushReplicationFilterModule";
 
   private final Configuration config;
   private final WorkQueue workQueue;
@@ -89,25 +85,33 @@
   private Iterable<AbstractModule> detectFilterModules() {
     ImmutableList.Builder<AbstractModule> filterModulesBuilder = ImmutableList.builder();
 
-    for (String filterClassName : FILTER_MODULES_CLASS_NAMES) {
-      try {
-        @SuppressWarnings("unchecked")
-        Class<AbstractModule> filterClass = (Class<AbstractModule>) Class.forName(filterClassName);
-
-        AbstractModule filterModule = parentInjector.getInstance(filterClass);
-        // Check if the filterModule would be valid for creating a child Guice Injector
-        parentInjector.createChildInjector(filterModule);
-
-        filterModulesBuilder.add(filterModule);
-      } catch (NoClassDefFoundError | ClassNotFoundException e) {
-        log.atFine().withCause(e).log(
-            "Not loading %s because of missing the associated replication plugin", filterClassName);
-      } catch (Exception e) {
-        throw new ProvisionException(
-            "Unable to instantiate replication filter " + filterClassName, e);
-      }
+    if (config.pushReplicationFilterEnabled()) {
+      bindReplicationFilterClass(PUSH_REPLICATION_FILTER_MODULE, filterModulesBuilder);
+    }
+    if (config.pullRepllicationFilterEnabled()) {
+      bindReplicationFilterClass(PULL_REPLICATION_FILTER_MODULE, filterModulesBuilder);
     }
 
     return filterModulesBuilder.build();
   }
+
+  private void bindReplicationFilterClass(
+      String filterClassName, ImmutableList.Builder<AbstractModule> filterModulesBuilder) {
+    try {
+      @SuppressWarnings("unchecked")
+      Class<AbstractModule> filterClass = (Class<AbstractModule>) Class.forName(filterClassName);
+
+      AbstractModule filterModule = parentInjector.getInstance(filterClass);
+      // Check if the filterModule would be valid for creating a child Guice Injector
+      parentInjector.createChildInjector(filterModule);
+
+      filterModulesBuilder.add(filterModule);
+    } catch (NoClassDefFoundError | ClassNotFoundException e) {
+      log.atWarning().withCause(e).log(
+          "Not loading %s because of missing the associated replication plugin", filterClassName);
+    } catch (Exception e) {
+      throw new ProvisionException(
+          "Unable to instantiate replication filter " + filterClassName, e);
+    }
+  }
 }

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 7547fd9..d7f72aa 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md

@@ -95,6 +95,16 @@
 :   Enable the use of a shared ref-database
     Defaults: true
 
+```ref-database.pushReplicationFilterClassEnabled```
+:   Enable the filtering of push replication events checking their
+    up-to-date status with the global-refdb.
+    Defaults: true
+
+```ref-database.pullReplicationFilterClassEnabled```
+:   Enable the filtering of pull replication events checking their
+    up-to-date status with the global-refdb.
+    Defaults: true
+
 ```ref-database.replicationLagEnabled```
 :   Enable the metrics to trace the auto-replication lag between sites
     updating the `refs/multi-site/version/*` to the _epoch_ timestamp in