diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index 3266cb1..8ab3d62 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -1281,6 +1281,39 @@
 }
 ----
 
+== Trace Event origin
+
+When plugins are installed in a multi-master setups it can be useful to know
+the Gerrit `instanceId` of the server that has generated an Event.
+
+E.g. A plugin that sends an instance message for every comment on a change may
+want to react only if the event is generated on the local Gerrit master, for
+avoiding duplicating the notifications.
+
+If link:config-gerrit.html[instanceId] is set, each Event will contain its
+origin in the `instanceId` field.
+
+Here and example of ref-updated JSON event payload with `instanceId`:
+
+[source,json]
+---
+{
+  "submitter": {
+    "name": "Administrator",
+    "email": "admin@example.com",
+    "username": "admin"
+  },
+  "refUpdate": {
+    "oldRev": "a69fc95c7aad5ad41c618d31548b8af835d2959a",
+    "newRev": "31da6556d638a74e5370b62f83e8007f94abb7c6",
+    "refName": "refs/changes/01/1/meta",
+    "project": "test"
+  },
+  "type": "ref-updated",
+  "eventCreatedOn": 1588849085,
+  "instanceId": "instance1"
+}
+---
 
 [[capabilities]]
 == Plugin Owned Capabilities
diff --git a/java/com/google/gerrit/acceptance/EventRecorder.java b/java/com/google/gerrit/acceptance/EventRecorder.java
index cab6b58..563c2ef 100644
--- a/java/com/google/gerrit/acceptance/EventRecorder.java
+++ b/java/com/google/gerrit/acceptance/EventRecorder.java
@@ -40,7 +40,7 @@
 
 public class EventRecorder {
   private final RegistrationHandle eventListenerRegistration;
-  private final ListMultimap<String, RefEvent> recordedEvents;
+  private final ListMultimap<String, Event> recordedEvents;
 
   @Singleton
   public static class Factory {
@@ -79,6 +79,8 @@
                       refEventKey(
                           event.getType(), event.getProjectNameKey().get(), event.getRefName());
                   recordedEvents.put(key, event);
+                } else {
+                  recordedEvents.put(e.type, e);
                 }
               }
 
@@ -158,6 +160,17 @@
     return events;
   }
 
+  public ImmutableList<Event> getGenericEvents(String type, int expectedSize) {
+    if (expectedSize == 0) {
+      assertThat(recordedEvents).doesNotContainKey(type);
+      return ImmutableList.of();
+    }
+    assertThat(recordedEvents).containsKey(type);
+    ImmutableList<Event> events = FluentIterable.from(recordedEvents.get(type)).toList();
+    assertThat(events).hasSize(expectedSize);
+    return events;
+  }
+
   public void assertNoRefUpdatedEvents(String project, String branch) throws Exception {
     getRefUpdatedEvents(project, branch, 0);
   }
diff --git a/java/com/google/gerrit/server/events/Event.java b/java/com/google/gerrit/server/events/Event.java
index c07987a..4cf4a5a 100644
--- a/java/com/google/gerrit/server/events/Event.java
+++ b/java/com/google/gerrit/server/events/Event.java
@@ -19,6 +19,7 @@
 public abstract class Event {
   public final String type;
   public long eventCreatedOn = TimeUtil.nowMs() / 1000L;
+  public String instanceId;
 
   protected Event(String type) {
     this.type = type;
diff --git a/java/com/google/gerrit/server/events/EventBroker.java b/java/com/google/gerrit/server/events/EventBroker.java
index 32b20fb..728dd01 100644
--- a/java/com/google/gerrit/server/events/EventBroker.java
+++ b/java/com/google/gerrit/server/events/EventBroker.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.server.events;
 
 import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.BranchNameKey;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.PatchSet;
@@ -23,6 +24,7 @@
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.config.GerritInstanceId;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.permissions.ChangePermission;
 import com.google.gerrit.server.permissions.PermissionBackend;
@@ -65,18 +67,22 @@
 
   protected final ChangeNotes.Factory notesFactory;
 
+  protected final String gerritInstanceId;
+
   @Inject
   public EventBroker(
       PluginSetContext<UserScopedEventListener> listeners,
       PluginSetContext<EventListener> unrestrictedListeners,
       PermissionBackend permissionBackend,
       ProjectCache projectCache,
-      ChangeNotes.Factory notesFactory) {
+      ChangeNotes.Factory notesFactory,
+      @Nullable @GerritInstanceId String gerritInstanceId) {
     this.listeners = listeners;
     this.unrestrictedListeners = unrestrictedListeners;
     this.permissionBackend = permissionBackend;
     this.projectCache = projectCache;
     this.notesFactory = notesFactory;
+    this.gerritInstanceId = gerritInstanceId;
   }
 
   @Override
@@ -105,6 +111,7 @@
   }
 
   protected void fireEvent(Change change, ChangeEvent event) throws PermissionBackendException {
+    setInstanceId(event);
     for (PluginSetEntryContext<UserScopedEventListener> c : listeners) {
       CurrentUser user = c.call(UserScopedEventListener::getUser);
       if (isVisibleTo(change, user)) {
@@ -115,7 +122,9 @@
   }
 
   protected void fireEvent(Project.NameKey project, ProjectEvent event) {
+    setInstanceId(event);
     for (PluginSetEntryContext<UserScopedEventListener> c : listeners) {
+
       CurrentUser user = c.call(UserScopedEventListener::getUser);
       if (isVisibleTo(project, user)) {
         c.run(l -> l.onEvent(event));
@@ -126,6 +135,7 @@
 
   protected void fireEvent(BranchNameKey branchName, RefEvent event)
       throws PermissionBackendException {
+    setInstanceId(event);
     for (PluginSetEntryContext<UserScopedEventListener> c : listeners) {
       CurrentUser user = c.call(UserScopedEventListener::getUser);
       if (isVisibleTo(branchName, user)) {
@@ -136,6 +146,7 @@
   }
 
   protected void fireEvent(Event event) throws PermissionBackendException {
+    setInstanceId(event);
     for (PluginSetEntryContext<UserScopedEventListener> c : listeners) {
       CurrentUser user = c.call(UserScopedEventListener::getUser);
       if (isVisibleTo(event, user)) {
@@ -145,6 +156,10 @@
     fireEventForUnrestrictedListeners(event);
   }
 
+  protected void setInstanceId(Event event) {
+    event.instanceId = gerritInstanceId;
+  }
+
   protected boolean isVisibleTo(Project.NameKey project, CurrentUser user) {
     try {
       Optional<ProjectState> state = projectCache.get(project);
diff --git a/javatests/com/google/gerrit/acceptance/server/event/InstanceIdInEventIT.java b/javatests/com/google/gerrit/acceptance/server/event/InstanceIdInEventIT.java
new file mode 100644
index 0000000..a333c3c
--- /dev/null
+++ b/javatests/com/google/gerrit/acceptance/server/event/InstanceIdInEventIT.java
@@ -0,0 +1,85 @@
+// Copyright (C) 2020 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.server.event;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.NoHttpd;
+import com.google.gerrit.acceptance.config.GerritConfig;
+import com.google.gerrit.extensions.registration.DynamicItem;
+import com.google.gerrit.server.events.Event;
+import com.google.gerrit.server.events.EventDispatcher;
+import com.google.gerrit.server.events.EventTypes;
+import com.google.inject.Inject;
+import org.junit.Before;
+import org.junit.Test;
+
+@NoHttpd
+public class InstanceIdInEventIT extends AbstractDaemonTest {
+
+  public static class TestDispatcher {
+    private final DynamicItem<EventDispatcher> eventDispatcher;
+
+    @Inject
+    TestDispatcher(DynamicItem<EventDispatcher> eventDispatcher) {
+      this.eventDispatcher = eventDispatcher;
+    }
+
+    public void postEvent(TestEvent event) {
+      try {
+        eventDispatcher.get().postEvent(event);
+      } catch (Exception e) {
+        fail("Exception raised when posting Event " + e.getCause());
+      }
+    }
+  }
+
+  public static class TestEvent extends Event {
+    private static final String TYPE = "test-event-instance-id";
+
+    public TestEvent() {
+      super(TYPE);
+    }
+  }
+
+  @Inject private DynamicItem<EventDispatcher> eventDispatcher;
+  TestDispatcher testDispatcher;
+
+  @Before
+  public void setUp() throws Exception {
+    testDispatcher = new TestDispatcher(eventDispatcher);
+    EventTypes.register(TestEvent.TYPE, TestEvent.class);
+  }
+
+  @Test
+  @GerritConfig(name = "gerrit.instanceId", value = "testInstanceId")
+  public void shouldSetInstanceIdWhenDefined() {
+    testDispatcher.postEvent(new TestEvent());
+
+    ImmutableList<Event> events = eventRecorder.getGenericEvents(TestEvent.TYPE, 1);
+    assertThat(events.get(0).instanceId).isEqualTo("testInstanceId");
+  }
+
+  @Test
+  public void shouldNotSetInstanceIdWhenNotDefined() {
+    testDispatcher.postEvent(new TestEvent());
+
+    ImmutableList<Event> events = eventRecorder.getGenericEvents(TestEvent.TYPE, 1);
+    assertThat(events.get(0).instanceId).isNull();
+  }
+}