[ZOOKEEPER-1750] Race condition producing NPE in NIOServerCnxn.toString

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.5.0
• Fix Version/s: 3.4.6, 3.5.0
• Component/s: server
• Assignee: Rakesh Radhakrishnan
• Reporter: Helen Hastings
• Created: 30/Aug/13 22:57
• Updated: 13/Mar/14 18:16
• Resolved: 04/Oct/13 23:16

Description

The socket is closed and the variable "sock" is set to null for normal reasons, but the toString method is called before "sock" can be set again, producing a NullPointerException.

Stack trace:

2013-08-29 01:49:19,991 6277 [CommitProcWorkThread-3] WARN org.apache.zookeeper.server.WorkerService - Unexpected exception
java.lang.NullPointerException
at org.apach.zookeeper.server.NIOServerCnxn.toString(NIOServerCnxn.java:961)
at java.lang.String.valueOf(String.java:2854)
at java.lang.StringBuilder.append(StringBuilder.java:128)
at org.apache.zookeeper.server.NIOServerCnxn.process(NIOServerCnxn.java:1104)
at org.apache.zookeeper.server.WatchManager.triggerWatch(WatchManager.java:120)
at org.apache.zookeeper.server.WatchManager.triggerWatch(WatchManager.java:92)
at org.apache.zookeeper.server.DataTree.createNode(DataTree.java:544)
at org.apache.zookeeper.server.DataTree.processTxn(DataTree.java:805)
at org.apache.zookeeper.server.ZKDatabase.processTxn(ZKDatabase.java:319)
at org.apache.zookeeper.server.ZooKeeperServer.processTxn(ZooKeeperServer.java:967)
at org.apache.zookeeper.server.FinalRequestProcessor.processRequest(FinalRequestProcessor.java:115)
at org.apache.zookeeper.server.quorum.Leader$ToBeAppliedRequestProcessor.processRequest(Leader.java:859)
at org.apache.zookeeper.server.quorum.CommitProcessor$CommitWorkRequest.doWork(CommitProcessor.java:271)
at org.apache.zookeeper.server.WorkerService$ScheduledWorkRequest.run(WorkerService.java:152)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:722)