[HBASE-3056] Fix ordering in ZKWatcher constructor to prevent weird race condition

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.90.0
• Fix Version/s: 0.90.0
• Component/s: Zookeeper
• Hadoop Flags: Reviewed
• Assignee: Jonathan Gray
• Reporter: Jonathan Gray
• Created: 30/Sep/10 17:58
• Updated: 20/Nov/15 12:43
• Resolved: 30/Sep/10 18:22

Description

A small race condition in ZKWatcher leads to an NPE:

2010-09-30 10:56:36,028 INFO  [Thread-217] zookeeper.ZKUtil(93): hconnection opening connection to ZooKeeper with quorum (localhost:21815)
2010-09-30 10:56:36,036 DEBUG [Thread-217-EventThread] zookeeper.ZooKeeperWatcher(184): hconnection Received ZooKeeper Event, type=None, state=SyncConnected, path=null
2010-09-30 10:56:36,036 ERROR [Thread-217-EventThread] zookeeper.ClientCnxn$EventThread(490): Error while calling watcher 
java.lang.NullPointerException
	at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.connectionEvent(ZooKeeperWatcher.java:243)
	at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.process(ZooKeeperWatcher.java:193)
	at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:488)