HADOOP 9871. Fix intermittent findbugs warnings in DefaultMetricsSystem. (Junping Du via llu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1514025 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -8,6 +8,9 @@ Release 2.3.0 - UNRELEASED
 
   IMPROVEMENTS
 
+    HADOOP 9871. Fix intermittent findbugs warnings in DefaultMetricsSystem.
+    (Junping Du via llu)
+
     HADOOP-9319. Update bundled LZ4 source to r99. (Binglin Chang via llu)
 
     HADOOP-9432 Add support for markdown .md files in site documentation (stevel)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/DefaultMetricsSystem.java

@@ -38,8 +38,8 @@ public enum DefaultMetricsSystem {
   private AtomicReference<MetricsSystem> impl =
       new AtomicReference<MetricsSystem>(new MetricsSystemImpl());
   volatile boolean miniClusterMode = false;
-  final UniqueNames mBeanNames = new UniqueNames();
-  final UniqueNames sourceNames = new UniqueNames();
+  transient final UniqueNames mBeanNames = new UniqueNames();
+  transient final UniqueNames sourceNames = new UniqueNames();
 
   /**
    * Convenience method to initialize the metrics system