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From "Michael Han (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1669) Operations to server will be timed-out while thousands of sessions expired same time
Date Thu, 13 Jul 2017 04:55:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16085182#comment-16085182
] 

Michael Han commented on ZOOKEEPER-1669:
----------------------------------------

I don't think there is any plans or anyone is actively working on this issue. It seems to
be a good performance improvement that worth doing though.
[~sun.cheney] If you have a fix are you willing to submit a patch? I can help review it. Also,
if you can share your use case here that will greatly benefit the community.

> Operations to server will be timed-out while thousands of sessions expired same time
> ------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1669
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1669
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: server
>    Affects Versions: 3.3.5
>            Reporter: tokoot
>              Labels: performance
>
> If there are thousands of clients, and most of them disconnect with server same time(client
restarted or servers partitioned with clients), the server will busy to close those "connections"
and become unavailable. The problem is in following:
>   private void closeSessionWithoutWakeup(long sessionId) {
>       HashSet<NIOServerCnxn> cnxns;
>           synchronized (this.cnxns) {
>               cnxns = (HashSet<NIOServerCnxn>)this.cnxns.clone();  // other thread
will block because of here
>           }
>       ...
>   }



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