YARN-10739. GenericEventHandler.printEventQueueDetails causes RM recovery to take too much time. Contributed by Qi Zhu.

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

@@ -25,7 +25,11 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
+import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
 import org.apache.hadoop.yarn.metrics.EventTypeMetrics;
 import org.apache.hadoop.yarn.util.Clock;
 import org.apache.hadoop.yarn.util.MonotonicClock;
@@ -93,6 +97,8 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
 
   private Clock clock = new MonotonicClock();
 
+  private ThreadPoolExecutor printEventDetailsExecutor;
+
   /**
    * The thread name for dispatcher.
    */
@@ -179,6 +185,15 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
                     YARN_DISPATCHER_PRINT_EVENTS_INFO_THRESHOLD,
             YarnConfiguration.
                     DEFAULT_YARN_DISPATCHER_PRINT_EVENTS_INFO_THRESHOLD);
+
+    ThreadFactory threadFactory = new ThreadFactoryBuilder()
+        .setNameFormat("PrintEventDetailsThread #%d")
+        .build();
+    // Thread pool for async print event details,
+    // to prevent wasting too much time for RM.
+    printEventDetailsExecutor = new ThreadPoolExecutor(
+        1, 5, 10, TimeUnit.SECONDS,
+        new LinkedBlockingQueue<>(), threadFactory);
   }
 
   @Override
@@ -222,6 +237,7 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
         LOG.warn("Interrupted Exception while stopping", ie);
       }
     }
+    printEventDetailsExecutor.shutdownNow();
 
     // stop all the components
     super.serviceStop();
@@ -319,7 +335,7 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
       if (qSize != 0 && qSize % detailsInterval == 0
               && lastEventDetailsQueueSizeLogged != qSize) {
         lastEventDetailsQueueSizeLogged = qSize;
-        printEventQueueDetails();
+        printEventDetailsExecutor.submit(this::printEventQueueDetails);
         printTrigger = true;
       }
       int remCapacity = eventQueue.remainingCapacity();

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

@@ -187,8 +187,6 @@ public class TestAsyncDispatcher {
         when(event.getType()).thenReturn(TestEnum.TestEventType);
         dispatcher.getEventHandler().handle(event);
       }
-      verify(log, atLeastOnce()).info("Event type: TestEventType, " +
-              "Event record counter: 5000");
       Thread.sleep(2000);
       //Make sure more than one event to take
       verify(log, atLeastOnce()).