[jira] [Commented] (ZOOKEEPER-1669) Operations to server will be timed-out while thousands of sessions expired same time

["Jacky007 (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13603262#comment-13603262 ] 

Jacky007 commented on ZOOKEEPER-1669:
-------------------------------------

We have paid for this. But the fix is simple, you can hash it when the session is created, and find from hash when close it. :)
                
> 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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