Merge -c 1186542 from trunk to branch-0.23 to complete fix for MAPREDUCE-3208.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1186544 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -1643,6 +1643,9 @@ Release 0.23.0 - Unreleased
 
     MAPREDUCE-2693. Fix NPE in job-blacklisting. (Hitesh Shah via acmurthy) 
 
+    MAPREDUCE-3208. Fix NPE task/container log appenders. (liangzhwa via
+    acmurthy) 
+
 Release 0.22.0 - Unreleased
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/TaskLogAppender.java

@@ -93,7 +93,9 @@ public class TaskLogAppender extends FileAppender {
   }
   
   public void flush() {
-    qw.flush();
+    if (qw != null) {
+      qw.flush();
+    }
   }
 
   @Override

hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/ContainerLogAppender.java

@@ -65,7 +65,9 @@ public class ContainerLogAppender extends FileAppender {
   }
   
   public void flush() {
-    qw.flush();
+    if (qw != null) {
+      qw.flush();
+    }
   }
 
   @Override