From 4356e8a5ef0ac6d11a34704b80ef360a710e623a Mon Sep 17 00:00:00 2001
From: Tsuyoshi Ozawa <ozawa@apache.org>
Date: Thu, 14 May 2015 10:20:45 +0900
Subject: [PATCH] HADOOP-11361. Fix a race condition in
 MetricsSourceAdapter.updateJmxCache. Contributed by Brahma Reddy Battula.

---
 hadoop-common-project/hadoop-common/CHANGES.txt |  3 +++
 .../metrics2/impl/MetricsSourceAdapter.java     | 17 +++++++----------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 207d1445f2c..5e6b9ea4c0d 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -674,6 +674,9 @@ Release 2.8.0 - UNRELEASED
     HADOOP-11962. Sasl message with MD5 challenge text shouldn't be LOG out
     even in debug level. (Junping Du via wheat9)
 
+    HADOOP-11361. Fix a race condition in MetricsSourceAdapter.updateJmxCache.
+    (Brahma Reddy Battula via ozawa)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSourceAdapter.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSourceAdapter.java
index cae9c3d7b4d..f3ddc916a39 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSourceAdapter.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSourceAdapter.java
@@ -154,31 +154,28 @@ class MetricsSourceAdapter implements DynamicMBean {
 
   private void updateJmxCache() {
     boolean getAllMetrics = false;
-    synchronized(this) {
+    synchronized (this) {
       if (Time.now() - jmxCacheTS >= jmxCacheTTL) {
         // temporarilly advance the expiry while updating the cache
         jmxCacheTS = Time.now() + jmxCacheTTL;
         if (lastRecs == null) {
           getAllMetrics = true;
         }
-      }
-      else {
+      } else {
         return;
       }
-    }
 
-    if (getAllMetrics) {
-      MetricsCollectorImpl builder = new MetricsCollectorImpl();
-      getMetrics(builder, true);
-    }
+      if (getAllMetrics) {
+        MetricsCollectorImpl builder = new MetricsCollectorImpl();
+        getMetrics(builder, true);
+      }
 
-    synchronized(this) {
       updateAttrCache();
       if (getAllMetrics) {
         updateInfoCache();
       }
       jmxCacheTS = Time.now();
-      lastRecs = null;  // in case regular interval update is not running
+      lastRecs = null; // in case regular interval update is not running
     }
   }