From d8f8a5823666f2d0a7af895b9dfe6eddb7490138 Mon Sep 17 00:00:00 2001
From: Enis Soztutar <enis@apache.org>
Date: Tue, 9 Sep 2014 18:35:53 -0700
Subject: [PATCH] HBASE-11923 Potential race condition in
 RecoverableZookeeper.checkZk() (Lars Hofhansl)

---
 .../apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
index 0614bfed747..ca359719488 100644
--- a/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
+++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/zookeeper/RecoverableZooKeeper.java
@@ -75,7 +75,7 @@ import org.htrace.TraceScope;
 public class RecoverableZooKeeper {
   private static final Log LOG = LogFactory.getLog(RecoverableZooKeeper.class);
   // the actual ZooKeeper client instance
-  volatile private ZooKeeper zk;
+  private ZooKeeper zk;
   private final RetryCounterFactory retryCounterFactory;
   // An identifier of this process in the cluster
   private final String identifier;
@@ -134,7 +134,7 @@ public class RecoverableZooKeeper {
    * @return The created Zookeeper connection object
    * @throws KeeperException
    */
-  protected ZooKeeper checkZk() throws KeeperException {
+  protected synchronized ZooKeeper checkZk() throws KeeperException {
     if (this.zk == null) {
       try {
         this.zk = new ZooKeeper(quorumServers, sessionTimeout, watcher);
@@ -146,7 +146,7 @@ public class RecoverableZooKeeper {
     return zk;
   }
 
-  public void reconnectAfterExpiration()
+  public synchronized void reconnectAfterExpiration()
         throws IOException, KeeperException, InterruptedException {
     if (zk != null) {
       LOG.info("Closing dead ZooKeeper connection, session" +