Index: src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWrapper.java =================================================================== --- src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWrapper.java (revision 956138) +++ src/main/java/org/apache/hadoop/hbase/zookeeper/ZooKeeperWrapper.java (working copy) @@ -219,11 +219,11 @@ } } - public void registerListener(Watcher watcher) { + public synchronized void registerListener(Watcher watcher) { listeners.add(watcher); } - public void unregisterListener(Watcher watcher) { + public synchronized void unregisterListener(Watcher watcher) { listeners.remove(watcher); }