[HBASE-19870] Fix the NPE in ReadOnlyZKClient#run

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0-beta-2, 2.0.0
• Hadoop Flags: Reviewed
• Assignee: Chia-Ping Tsai
• Reporter: Chia-Ping Tsai
• Created: 26/Jan/18 18:35
• Updated: 21/Mar/18 22:23
• Resolved: 29/Jan/18 08:37

Description

I notice a NPE from my jenkins.

2018-01-26 17:26:41,078 DEBUG [M:0;8546d406e429:40557-EventThread] zookeeper.ZKWatcher(443): replicationLogCleaner-0x161337ddc090004, quorum=localhost:56060, baseZNode=/hbase Received ZooKeeper Event, type=None, state=Disconnected, path=null
java.lang.NullPointerException
	at org.apache.hadoop.hbase.zookeeper.ReadOnlyZKClient.run(ReadOnlyZKClient.java:322)
	at java.lang.Thread.run(Thread.java:748)

If any zk task invokes the #onComplete late, the count of current requests will not zero and then the null from task queue will destroy the work thread in ReadOnlyZKClient.