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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2678) Large databases take a long time to regain a quorum
Date Mon, 13 Feb 2017 14:56:42 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15863783#comment-15863783
] 

ASF GitHub Bot commented on ZOOKEEPER-2678:
-------------------------------------------

Github user revans2 commented on the issue:

    https://github.com/apache/zookeeper/pull/157
  
    @rakeshadr If it makes you feel any better we have been running with an older version
of this patch in production for a while.  We have used it as part of a rolling upgrade at
least 10 times in production where if it were not there we would have had some very painful
outages. 
    
    I have also manually tested it at least 50 times shooting the leader under load (10,000
operations/second) on a 3.4 GB DB, watching it recover, and then validating the integrity
of the DB to be sure we didn't get any corruption.


> Large databases take a long time to regain a quorum
> ---------------------------------------------------
>
>                 Key: ZOOKEEPER-2678
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2678
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.4.9, 3.5.2
>            Reporter: Robert Joseph Evans
>            Assignee: Robert Joseph Evans
>             Fix For: 3.6.0
>
>
> I know this is long but please here me out.
> I recently inherited a massive zookeeper ensemble.  The snapshot is 3.4 GB on disk. 
Because of its massive size we have been running into a number of issues. There are lots of
problems that we hope to fix with tuning GC etc, but the big one right now that is blocking
us making a lot of progress on the rest of them is that when we lose a quorum because the
leader left, for what ever reason, it can take well over 5 mins for a new quorum to be established.
 So we cannot tune the leader without risking downtime.
> We traced down where the time was being spent and found that each server was clearing
the database so it would be read back in again before leader election even started.  Then
as part of the sync phase each server will write out a snapshot to checkpoint the progress
it made as part of the sync.
> I will be putting up a patch shortly with some proposed changes in it.



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