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From "Cheney Sun (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1669) Operations to server will be timed-out while thousands of sessions expired same time
Date Tue, 18 Jul 2017 10:57:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16091403#comment-16091403
] 

Cheney Sun commented on ZOOKEEPER-1669:
---------------------------------------

Looks like the issue is already addressed in [ZOOKEEPER-1347] and a patch was available, but
not fixed in 3.4, which is the latest stable version and the one we currently use. @Michael,
is it meaningful to porting the fix to older version, 3.4 or 3.3?

> 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
>            Assignee: Cheney Sun
>              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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