[ZOOKEEPER-1781] ZooKeeper Server fails if snapCount is set to 1

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.4.5
• Fix Version/s: 3.4.6, 3.5.0
• Component/s: quorum
• Hadoop Flags: Reviewed
• Assignee: Takashi Ohnishi
• Reporter: Takashi Ohnishi
• Created: 04/Oct/13 01:19
• Updated: 13/Mar/14 18:17
• Resolved: 07/Oct/13 23:38

Description

If snapCount is set to 1, ZooKeeper Server can start but it fails with the below error:

2013-10-02 18:09:07,600 [myid:1] - ERROR [SyncThread:1:SyncRequestProcessor@151] - Severe unrecoverable error, exiting
java.lang.IllegalArgumentException: n must be positive
at java.util.Random.nextInt(Random.java:300)
at org.apache.zookeeper.server.SyncRequestProcessor.run(SyncRequestProcessor.java:93)

In source code, it maybe be supposed that snapCount must be 2 or more:

org.apache.zookeeper.server.SyncRequestProcessor.java

     91             // we do this in an attempt to ensure that not all ofthe servers
     92             // in the ensemble take a snapshot at the same time
     93             int randRoll = r.nextInt(snapCount/2);

I think this supposition is not bad because snapCount = 1 is not realistic setting...
But, it may be better to mention this restriction in documentation or add a validation in the source code.