YARN-9491. TestApplicationMasterServiceFair#ApplicationMasterServiceTestBase.testUpdateTrackingUrl fails intermittent. Contributed by Prabhu Joseph.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/ApplicationMasterServiceTestBase.java

@@ -464,6 +464,10 @@ public abstract class ApplicationMasterServiceTestBase {
     allocateRequest.setTrackingUrl(newTrackingUrl);
 
     am1.allocate(allocateRequest);
+
+    // wait until RMAppAttemptEventType.STATUS_UPDATE is handled
+    rm.drainEvents();
+
     Assert.assertEquals(newTrackingUrl, rm.getRMContext().getRMApps().get(
         app1.getApplicationId()).getOriginalTrackingUrl());