YARN-11870 When manually switching Active to Standby, the ActiveStandbyElectorLock is not released.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-client/src/test/java/org/apache/hadoop/yarn/client/TestRMFailover.java

@@ -19,6 +19,7 @@
 package org.apache.hadoop.yarn.client;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.assertNull;
@@ -459,4 +460,29 @@ public void testUncaughtExceptionHandlerWithoutHA()
 
     verify(spyRTEHandler).uncaughtException(testThread, rte);
   }
+
+  @Test
+  public void testTransitionedToStandbyWhenAutoFailover()
+      throws YarnException, InterruptedException, IOException {
+    conf.set(YarnConfiguration.RM_CLUSTER_ID, "yarn-test-cluster");
+    conf.set(YarnConfiguration.RM_ZK_ADDRESS, hostPort);
+    conf.setInt(YarnConfiguration.RM_ZK_TIMEOUT_MS, 2000);
+
+    cluster.init(conf);
+    cluster.start();
+
+    int activeRMIndex = cluster.getActiveRMIndex();
+    assertNotEquals(-1, activeRMIndex, "RM never turned active");
+    verifyConnections();
+
+    HAServiceProtocol.StateChangeRequestInfo requestInfo = new HAServiceProtocol.StateChangeRequestInfo(
+        HAServiceProtocol.RequestSource.REQUEST_BY_USER_FORCED);
+    // transit the active RM to standby.
+    getAdminService(activeRMIndex).transitionToStandby(requestInfo);
+    verifyRMTransitionToStandby(cluster.getResourceManager(activeRMIndex));
+    // the standby RM transition to active.
+    int newActiveRMIndex = (activeRMIndex + 1) % 2;
+    assertEquals(newActiveRMIndex, cluster.getActiveRMIndex(), "Failover failed");
+    verifyConnections();
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java

@@ -1586,6 +1586,8 @@ synchronized void transitionToStandby(boolean initialize)
     if (state == HAServiceProtocol.HAServiceState.ACTIVE) {
       stopActiveServices();
       reinitialize(initialize);
+      EmbeddedElector elector = rmContext.getLeaderElectorService();
+      if (elector != null) elector.rejoinElection();
     }
     LOG.info("Transitioned to standby state");
   }