[jira] [Commented] (ZOOKEEPER-571) support balancing of client load across servers in an ensemble

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

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-571?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15963101#comment-15963101 ] 

Marco P. commented on ZOOKEEPER-571:
------------------------------------

Related: https://issues.apache.org/jira/browse/ZOOKEEPER-2748

> support balancing of client load across servers in an ensemble
> --------------------------------------------------------------
>
>                 Key: ZOOKEEPER-571
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-571
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: quorum, server
>            Reporter: Patrick Hunt
>
> Currently the ensemble does not ensure a balanced load across servers in an ensemble. Clients randomly connect to
> a server, which typically balances the number of sessions. However there are problems with this:
> 1) session count is balanced, but not session load
> 2) if server A goes down all of the sessions on that server migrate to other servers in the cluster randomly, this is fine, however
> when server A comes back into service it will have no sessions, and migration of sessions from other servers may take time
> The quorum should probably have some way of broadcasting load, and occasionally re-balance the sessions based on
> this information. Might be tricky though, want to ensure that we aren't constantly ping-ponging sessions to servers.
> Probably need some hysteresis as well as limit the frequency. Real time tuning would need to be supported.



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