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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2774) Ephemeral znode will not be removed when sesstion timeout, if the system time of ZooKeeper node changes unexpectedly.
Date Thu, 18 May 2017 18:17:04 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16016193#comment-16016193
] 

ASF GitHub Bot commented on ZOOKEEPER-2774:
-------------------------------------------

Github user hanm commented on the issue:

    https://github.com/apache/zookeeper/pull/253
  
    LGTM - all unit test passed. The Jenkins check failed because it has findbug warnings
and that is a known issue for branch-3.4. I will merge this to branch-3.4 soon.
    
    One suggestion, in future pull request, please provide a descriptive title and a brief
description of what the pull request did.


> Ephemeral znode will not be removed when sesstion timeout, if the system time of ZooKeeper
node changes unexpectedly.
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2774
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2774
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.4.8, 3.4.9, 3.4.10
>         Environment: Centos6.5
>            Reporter: JiangJiafu
>
> 1. Deploy a ZooKeeper cluster with one node.
> 2. Create a Ephemeral znode.
> 3. Change the system time of the ZooKeeper node to a earlier point.
> 4. Disconnect the client with the ZooKeeper server.
> Then the ephemeral znode will exist for a long time even when session timeout.
> I have read the ZooKeeper source code and I find the code int SessionTrackerImpl.java,
> {code:title=SessionTrackerImpl.java|borderStyle=solid}
>     @Override
>     synchronized public void run() {
>         try {
>             while (running) {
>                 currentTime = System.currentTimeMillis();
>                 if (nextExpirationTime > currentTime) {
>                     this.wait(nextExpirationTime - currentTime);
>                     continue;
>                 }
>                 SessionSet set;
>                 set = sessionSets.remove(nextExpirationTime);
>                 if (set != null) {
>                     for (SessionImpl s : set.sessions) {
>                         setSessionClosing(s.sessionId);
>                         expirer.expire(s);
>                     }
>                 }
>                 nextExpirationTime += expirationInterval;
>             }
>         } catch (InterruptedException e) {
>             handleException(this.getName(), e);
>         }
>         LOG.info("SessionTrackerImpl exited loop!");
>     }
> {code}
> I think it may be better to use System.nanoTime(), not System.currentTimeMillis, because
the later can be changed manually or automatically by a NTP client. 



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