MAPREDUCE-3586. Modified CompositeService to avoid duplicate stop operations thereby solving race conditions in MR AM shutdown. (vinodkv)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1221950 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -352,6 +352,9 @@ Release 0.23.1 - Unreleased
     MAPREDUCE-3588. Fixed bin/yarn which was broken by MAPREDUCE-3366 so that
     yarn daemons can start. (Arun C Murthy via vinodkv)
 
+    MAPREDUCE-3586. Modified CompositeService to avoid duplicate stop operations
+    thereby solving race conditions in MR AM shutdown. (vinodkv)
+
 Release 0.23.0 - 2011-11-01 
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/service/CompositeService.java

@@ -81,6 +81,10 @@ public class CompositeService extends AbstractService {
   }
 
   public synchronized void stop() {
+    if (this.getServiceState() == STATE.STOPPED) {
+      // The base composite-service is already stopped, don't do anything again.
+      return;
+    }
     if (serviceList.size() > 0) {
       stop(serviceList.size() - 1);
     }

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestCompositeService.java

@@ -88,6 +88,14 @@ public class TestCompositeService {
           ((NUM_OF_SERVICES - 1) - i), services[i].getCallSequenceNumber());
     }
 
+    // Try to stop again. This should be a no-op.
+    serviceManager.stop();
+    // Verify that stop() call sequence numbers for every service don't change.
+    for (int i = 0; i < NUM_OF_SERVICES; i++) {
+      assertEquals("For " + services[i]
+          + " service, stop() call sequence number should have been ",
+          ((NUM_OF_SERVICES - 1) - i), services[i].getCallSequenceNumber());
+    }
   }
 
   @Test
@@ -153,7 +161,7 @@ public class TestCompositeService {
 
     serviceManager.start();
 
-    // Start the composite service
+    // Stop the composite service
     try {
       serviceManager.stop();
     } catch (YarnException e) {