MAPREDUCE-5689. MRAppMaster does not preempt reducers when scheduled maps cannot be fulfilled. (lohit via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1555161 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -267,6 +267,9 @@ Release 2.4.0 - UNRELEASED
     MAPREDUCE-5685. Fixed a bug with JobContext getCacheFiles API inside the
     WrappedReducer class. (Yi Song via vinodkv)
 
+    MAPREDUCE-5689. MRAppMaster does not preempt reducers when scheduled maps 
+    cannot be fulfilled. (lohit via kasha)
+
 Release 2.3.0 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/rm/RMContainerAllocator.java

@@ -229,7 +229,8 @@ public class RMContainerAllocator extends RMContainerRequestor
 
     int completedMaps = getJob().getCompletedMaps();
     int completedTasks = completedMaps + getJob().getCompletedReduces();
-    if (lastCompletedTasks != completedTasks) {
+    if ((lastCompletedTasks != completedTasks) ||
+          (scheduledRequests.maps.size() > 0)) {
       lastCompletedTasks = completedTasks;
       recalculateReduceSchedule = true;
     }

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRMContainerAllocator.java

@@ -1604,6 +1604,21 @@ public class TestRMContainerAllocator {
         numPendingReduces, 
         maxReduceRampupLimit, reduceSlowStart);
     verify(allocator).rampDownReduces(anyInt());
+
+    // Test reduce ramp-down for when there are scheduled maps
+    // Since we have two scheduled Maps, rampDownReducers 
+    // should be invoked twice.
+    scheduledMaps = 2;
+    assignedReduces = 2;
+    doReturn(10 * 1024).when(allocator).getMemLimit();
+    allocator.scheduleReduces(
+        totalMaps, succeededMaps, 
+        scheduledMaps, scheduledReduces, 
+        assignedMaps, assignedReduces, 
+        mapResourceReqt, reduceResourceReqt, 
+        numPendingReduces, 
+        maxReduceRampupLimit, reduceSlowStart);
+    verify(allocator, times(2)).rampDownReduces(anyInt());
   }
 
   private static class RecalculateContainerAllocator extends MyContainerAllocator {