YARN=5526. DrainDispacher#serviceStop blocked if setDrainEventsOnStop invoked (sandflee via Varun Saxena)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/event/AsyncDispatcher.java

@@ -148,7 +148,7 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
               YarnConfiguration.DEFAULT_DISPATCHER_DRAIN_EVENTS_TIMEOUT);
 
       synchronized (waitForDrained) {
-        while (!drained && eventHandlingThread != null
+        while (!isDrained() && eventHandlingThread != null
             && eventHandlingThread.isAlive()
             && System.currentTimeMillis() < endTime) {
           waitForDrained.wait(1000);
@@ -303,4 +303,8 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
   protected boolean isEventThreadWaiting() {
     return eventHandlingThread.getState() == Thread.State.WAITING;
   }
+
+  protected boolean isDrained() {
+    return drained;
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/event/DrainDispatcher.java

@@ -94,6 +94,11 @@ public class DrainDispatcher extends AsyncDispatcher {
     };
   }
 
+  @Override
+  protected boolean isDrained() {
+    return drained;
+  }
+
   @Override
   protected void serviceStop() throws Exception {
     stopped = true;