YARN-8222. Fix potential NPE when gets RMApp from RM context. Contributed by Tao Yang.

(cherry picked from commit 251f528814c4a4647cac0af6effb9a73135db180)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmcontainer/RMContainerImpl.java

@@ -45,6 +45,7 @@ import org.apache.hadoop.yarn.event.EventHandler;
 import org.apache.hadoop.yarn.server.api.protocolrecords.NMContainerStatus;
 import org.apache.hadoop.yarn.server.resourcemanager.RMContext;
 import org.apache.hadoop.yarn.server.resourcemanager.nodelabels.RMNodeLabelsManager;
+import org.apache.hadoop.yarn.server.resourcemanager.rmapp.RMApp;
 import org.apache.hadoop.yarn.server.resourcemanager.rmapp.RMAppRunningOnNodeEvent;
 import org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttempt;
 import org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptEvent;
@@ -709,21 +710,22 @@ public class RMContainerImpl implements RMContainer {
     private static void updateAttemptMetrics(RMContainerImpl container) {
       // If this is a preempted container, update preemption metrics
       Resource resource = container.getContainer().getResource();
-      RMAppAttempt rmAttempt = container.rmContext.getRMApps()
-          .get(container.getApplicationAttemptId().getApplicationId())
-          .getCurrentAppAttempt();
-
-      if (rmAttempt != null) {
-        long usedMillis = container.finishTime - container.creationTime;
-        rmAttempt.getRMAppAttemptMetrics()
-            .updateAggregateAppResourceUsage(resource, usedMillis);
-        // If this is a preempted container, update preemption metrics
-        if (ContainerExitStatus.PREEMPTED == container.finishedStatus
-            .getExitStatus()) {
+      RMApp app = container.rmContext.getRMApps()
+          .get(container.getApplicationAttemptId().getApplicationId());
+      if (app != null) {
+        RMAppAttempt rmAttempt = app.getCurrentAppAttempt();
+        if (rmAttempt != null) {
+          long usedMillis = container.finishTime - container.creationTime;
           rmAttempt.getRMAppAttemptMetrics()
-              .updatePreemptionInfo(resource, container);
-          rmAttempt.getRMAppAttemptMetrics()
-              .updateAggregatePreemptedAppResourceUsage(resource, usedMillis);
+              .updateAggregateAppResourceUsage(resource, usedMillis);
+          // If this is a preempted container, update preemption metrics
+          if (ContainerExitStatus.PREEMPTED == container.finishedStatus
+              .getExitStatus()) {
+            rmAttempt.getRMAppAttemptMetrics()
+                .updatePreemptionInfo(resource, container);
+            rmAttempt.getRMAppAttemptMetrics()
+                .updateAggregatePreemptedAppResourceUsage(resource, usedMillis);
+          }
         }
       }
     }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/SchedulerApplicationAttempt.java

@@ -1166,12 +1166,13 @@ public class SchedulerApplicationAttempt implements SchedulableEntity {
       return;
     }
 
-    RMAppAttempt attempt =
-        rmContext.getRMApps().get(attemptId.getApplicationId())
-          .getCurrentAppAttempt();
-    if (attempt != null) {
-      attempt.getRMAppAttemptMetrics().incNumAllocatedContainers(containerType,
-        requestType);
+    RMApp app = rmContext.getRMApps().get(attemptId.getApplicationId());
+    if (app != null) {
+      RMAppAttempt attempt = app.getCurrentAppAttempt();
+      if (attempt != null) {
+        attempt.getRMAppAttemptMetrics()
+            .incNumAllocatedContainers(containerType, requestType);
+      }
     }
   }