YARN-6515. Fix warnings from Spotbugs in hadoop-yarn-server-nodemanager. Contributed by Naganarasimha G R.

(cherry picked from commit 1a18d5e514d13aa3a88e9b6089394a27296d6bc3)

 Conflicts:
	hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ContainerLocalizer.java

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/NodeStatusUpdaterImpl.java

@@ -661,7 +661,6 @@ public class NodeStatusUpdaterImpl extends AbstractService implements
   public void removeOrTrackCompletedContainersFromContext(
       List<ContainerId> containerIds) throws IOException {
     Set<ContainerId> removedContainers = new HashSet<ContainerId>();
-    Set<ContainerId> removedNullContainers = new HashSet<ContainerId>();
 
     pendingContainersToRemove.addAll(containerIds);
     Iterator<ContainerId> iter = pendingContainersToRemove.iterator();
@@ -671,7 +670,6 @@ public class NodeStatusUpdaterImpl extends AbstractService implements
       Container nmContainer = context.getContainers().get(containerId);
       if (nmContainer == null) {
         iter.remove();
-        removedNullContainers.add(containerId);
       } else if (nmContainer.getContainerState().equals(
         org.apache.hadoop.yarn.server.nodemanager.containermanager.container.ContainerState.DONE)) {
         context.getContainers().remove(containerId);
@@ -734,11 +732,12 @@ public class NodeStatusUpdaterImpl extends AbstractService implements
   public void removeVeryOldStoppedContainersFromCache() {
     synchronized (recentlyStoppedContainers) {
       long currentTime = System.currentTimeMillis();
-      Iterator<ContainerId> i =
-          recentlyStoppedContainers.keySet().iterator();
+      Iterator<Entry<ContainerId, Long>> i =
+          recentlyStoppedContainers.entrySet().iterator();
       while (i.hasNext()) {
-        ContainerId cid = i.next();
-        if (recentlyStoppedContainers.get(cid) < currentTime) {
+        Entry<ContainerId, Long> mapEntry = i.next();
+        ContainerId cid = mapEntry.getKey();
+        if (mapEntry.getValue() < currentTime) {
           if (!context.getContainers().containsKey(cid)) {
             i.remove();
             try {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ContainerLocalizer.java

@@ -17,6 +17,8 @@
 */
 package org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer;
 
+import static org.apache.hadoop.util.Shell.getAllShells;
+
 import com.google.common.base.Preconditions;
 import java.io.DataInputStream;
 import java.io.File;
@@ -31,6 +33,7 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Set;
 import java.util.Stack;
 import java.util.concurrent.Callable;
@@ -83,8 +86,6 @@ import org.apache.hadoop.yarn.util.FSDownload;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
 
-import static org.apache.hadoop.util.Shell.getAllShells;
-
 public class ContainerLocalizer {
 
   static final Logger LOG =
@@ -350,13 +351,13 @@ public class ContainerLocalizer {
     final List<LocalResourceStatus> currentResources =
       new ArrayList<LocalResourceStatus>();
     // TODO: Synchronization??
-    for (Iterator<LocalResource> i = pendingResources.keySet().iterator();
-         i.hasNext();) {
-      LocalResource rsrc = i.next();
+    for (Iterator<Entry<LocalResource, Future<Path>>> i =
+        pendingResources.entrySet().iterator(); i.hasNext();) {
+      Entry<LocalResource, Future<Path>> mapEntry = i.next();
       LocalResourceStatus stat =
         recordFactory.newRecordInstance(LocalResourceStatus.class);
-      stat.setResource(rsrc);
-      Future<Path> fPath = pendingResources.get(rsrc);
+      stat.setResource(mapEntry.getKey());
+      Future<Path> fPath = mapEntry.getValue();
       if (fPath.isDone()) {
         try {
           Path localPath = fPath.get();

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainerMetrics.java

@@ -130,7 +130,7 @@ public class ContainerMetrics implements MetricsSource {
   /**
    * Simple metrics cache to help prevent re-registrations.
    */
-  protected final static Map<ContainerId, ContainerMetrics>
+  private final static Map<ContainerId, ContainerMetrics>
       usageMetrics = new HashMap<>();
   // Create a timer to unregister container metrics,
   // whose associated thread run as a daemon.