YARN-5483. Optimize RMAppAttempt#pullJustFinishedContainers. Contributed by sandflee

hadoop-yarn-project/CHANGES.txt

@@ -16,6 +16,9 @@ Release 2.6.5 - UNRELEASED
     YARN-5262. Optimize sending RMNodeFinishedContainersPulledByAMEvent for
     every AM heartbeat (Rohith Sharma K S via jlowe)
 
+    YARN-5483. Optimize RMAppAttempt#pullJustFinishedContainers (sandflee via
+    jlowe)
+
   BUG FIXES
 
     YARN-2046. Out of band heartbeats are sent only on container kill and

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/RMAppAttemptImpl.java

@@ -28,6 +28,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
@@ -36,7 +37,6 @@ import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
 
 import javax.crypto.SecretKey;
 
-import org.apache.commons.lang.StringUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
@@ -692,15 +692,17 @@ public class RMAppAttemptImpl implements RMAppAttempt, Recoverable {
 
       // Mark every containerStatus as being sent to AM though we may return
       // only the ones that belong to the current attempt
-      boolean keepContainersAcressAttempts = this.submissionContext
+      boolean keepContainersAcrossAppAttempts = this.submissionContext
           .getKeepContainersAcrossApplicationAttempts();
-      for (NodeId nodeId:justFinishedContainers.keySet()) {
-
-        // Clear and get current values
-        List<ContainerStatus> finishedContainers = justFinishedContainers.put
-            (nodeId, new ArrayList<ContainerStatus>());
+      for (Map.Entry<NodeId, List<ContainerStatus>> entry:
+          justFinishedContainers.entrySet()) {
+        NodeId nodeId = entry.getKey();
+        List<ContainerStatus> finishedContainers = entry.getValue();
+        if (finishedContainers.isEmpty()) {
+          continue;
+        }
 
-        if (keepContainersAcressAttempts) {
+        if (keepContainersAcrossAppAttempts) {
           returnList.addAll(finishedContainers);
         } else {
           // Filter out containers from previous attempt
@@ -712,12 +714,11 @@ public class RMAppAttemptImpl implements RMAppAttempt, Recoverable {
           }
         }
 
-        if (!finishedContainers.isEmpty()) {
-          finishedContainersSentToAM.putIfAbsent(nodeId,
-              new ArrayList<ContainerStatus>());
-          finishedContainersSentToAM.get(nodeId).addAll(finishedContainers);
-        }
+        finishedContainersSentToAM.putIfAbsent(nodeId,
+            new ArrayList<ContainerStatus>());
+        finishedContainersSentToAM.get(nodeId).addAll(finishedContainers);
       }
+      justFinishedContainers.clear();
 
       return returnList;
     } finally {