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https://issues.apache.org/jira/browse/ZOOKEEPER-1669?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13608802#comment-13608802
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Jacky007 commented on ZOOKEEPER-1669:
-------------------------------------
I think it is. In one of our environment, there are tens of thousands
connections and 300~500/s close session(these clients create a connection for a
read, and close it immediately). The codes you described significantly affect
performance.
> 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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