HADOOP-11459. Fix recent findbugs in ActiveStandbyElector, NetUtils and ShellBasedIdMapping (Contributed by Vinayakumar B)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -670,7 +670,10 @@ Release 2.7.0 - UNRELEASED
 
     HADOOP-11446. S3AOutputStream should use shared thread pool to
     avoid OutOfMemoryError. (Ted Yu via stevel)	
-    
+
+    HADOOP-11459. Fix recent findbugs in ActiveStandbyElector, NetUtils
+    and ShellBasedIdMapping (vinayakumarb)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/ActiveStandbyElector.java

@@ -1064,7 +1064,9 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
     public void process(WatchedEvent event) {
       hasReceivedEvent.countDown();
       try {
-        hasSetZooKeeper.await(zkSessionTimeout, TimeUnit.MILLISECONDS);
+        if (!hasSetZooKeeper.await(zkSessionTimeout, TimeUnit.MILLISECONDS)) {
+          LOG.debug("Event received with stale zk");
+        }
         ActiveStandbyElector.this.processWatchEvent(
             zk, event);
       } catch (Throwable t) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetUtils.java

@@ -288,7 +288,7 @@ public class NetUtils {
       try {
         fqHost = SecurityUtil.getByName(host).getHostName();
         // slight race condition, but won't hurt
-        canonicalizedHostCache.put(host, fqHost);
+        canonicalizedHostCache.putIfAbsent(host, fqHost);
       } catch (UnknownHostException e) {
         fqHost = host;
       }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ShellBasedIdMapping.java

@@ -290,7 +290,7 @@ public class ShellBasedIdMapping implements IdMappingServiceProvider {
     return true;
   }
 
-  private void initStaticMapping() throws IOException {
+  private synchronized void initStaticMapping() throws IOException {
     staticMapping = new StaticMapping(
         new HashMap<Integer, Integer>(), new HashMap<Integer, Integer>());
     if (staticMappingFile.exists()) {