YARN-3941. Proportional Preemption policy should try to avoid sending duplicate PREEMPT_CONTAINER event to scheduler. (Sunil G via wangda)

hadoop-yarn-project/CHANGES.txt

@@ -664,6 +664,8 @@ Release 2.8.0 - UNRELEASED
 
     YARN-3956. Fix TestNodeManagerHardwareUtils fails on Mac (Varun Vasudev via wangda)
 
+    YARN-3941. Proportional Preemption policy should try to avoid sending duplicate PREEMPT_CONTAINER event to scheduler. (Sunil G via wangda)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java

@@ -260,13 +260,16 @@ public class ProportionalCapacityPreemptionPolicy implements SchedulingEditPolic
                   SchedulerEventType.KILL_CONTAINER));
           preempted.remove(container);
         } else {
+          if (preempted.get(container) != null) {
+            // We already updated the information to scheduler earlier, we need
+            // not have to raise another event.
+            continue;
+          }
           //otherwise just send preemption events
           rmContext.getDispatcher().getEventHandler().handle(
               new ContainerPreemptEvent(appAttemptId, container,
                   SchedulerEventType.PREEMPT_CONTAINER));
-          if (preempted.get(container) == null) {
-            preempted.put(container, clock.getTime());
-          }
+          preempted.put(container, clock.getTime());
         }
       }
     }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/TestProportionalCapacityPreemptionPolicy.java

@@ -280,14 +280,14 @@ public class TestProportionalCapacityPreemptionPolicy {
     // requests reiterated
     when(mClock.getTime()).thenReturn(killTime / 2);
     policy.editSchedule();
-    verify(mDisp, times(20)).handle(argThat(new IsPreemptionRequestFor(appC)));
+    verify(mDisp, times(10)).handle(argThat(new IsPreemptionRequestFor(appC)));
 
     // kill req sent
     when(mClock.getTime()).thenReturn(killTime + 1);
     policy.editSchedule();
-    verify(mDisp, times(30)).handle(evtCaptor.capture());
+    verify(mDisp, times(20)).handle(evtCaptor.capture());
     List<ContainerPreemptEvent> events = evtCaptor.getAllValues();
-    for (ContainerPreemptEvent e : events.subList(20, 30)) {
+    for (ContainerPreemptEvent e : events.subList(20, 20)) {
       assertEquals(appC, e.getAppId());
       assertEquals(KILL_CONTAINER, e.getType());
     }