[jira] [Commented] (ZOOKEEPER-1972) Fix invalid volatile long/int increment (++)

[Hongchao Deng (JIRA)]

    [ 
https://issues.apache.org/jira/browse/ZOOKEEPER-1972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14067628#comment-14067628
 ] 

Hongchao Deng commented on ZOOKEEPER-1972:
------------------------------------------

Thanks for review!

Please wait.
I am thinking about better way to resolve the tick in Leader and Learner.

> Fix invalid volatile long/int increment (++)
> --------------------------------------------
>
>                 Key: ZOOKEEPER-1972
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1972
>             Project: ZooKeeper
>          Issue Type: Sub-task
>    Affects Versions: 3.5.0
>            Reporter: Hongchao Deng
>            Assignee: Hongchao Deng
>             Fix For: 3.5.0
>
>         Attachments: ZOOKEEPER-1972.patch
>
>
> The findbugs complains about incrementing a volatile variable in 
> [AuthFastLeaderElection|https://github.com/apache/zookeeper/blob/087abf83684167ae56864fe4c3be0079fa653266/src/java/main/org/apache/zookeeper/server/quorum/AuthFastLeaderElection.java#L737]
>  and 
> [FastLeaderElection|https://github.com/apache/zookeeper/blob/087abf83684167ae56864fe4c3be0079fa653266/src/java/main/org/apache/zookeeper/server/quorum/FastLeaderElection.java]:
> {code}
> volatile long logicalclock; /* Election instance */
> ...
> logicalclock++;
> {code}
> Actually this is a bug. It should use AtomicLong here instead of volatile.
> Leader.java and 
> [QuorumPeer.java|https://github.com/apache/zookeeper/blob/087abf83684167ae56864fe4c3be0079fa653266/src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java#L428]
>  and LearnerHandler.java:
> {code}
> volatile int tick;
> {code}
> I don't think it needs volatile here. The tick is incremented only in 
> [Leader.java|https://github.com/apache/zookeeper/blob/087abf83684167ae56864fe4c3be0079fa653266/src/java/main/org/apache/zookeeper/server/quorum/Leader.java#L590]:
> {code}
>   synchronized (this) {
>           ...
>                     if (!tickSkip) {
>                         self.tick++;
>                     }
>   }
> {code}
> and it's protected by the synchronized statement. I just remove volatile 
> keyword.



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