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Date: Fri, 10 Feb 2017 15:05:42 +0000 (UTC)
From: "ASF GitHub Bot (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (ZOOKEEPER-2678) Large databases take a long
 time to regain a quorum
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archived-at: Fri, 10 Feb 2017 15:05:50 -0000


    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2678?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15861379#comment-15861379 ] 

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

Github user revans2 commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/159#discussion_r100552192
  
    --- Diff: src/java/main/org/apache/zookeeper/server/quorum/Learner.java ---
    @@ -498,14 +504,19 @@ else if (qp.getType() == Leader.SNAP) {
                                throw new Exception("changes proposed in reconfig");
                            }
                         }
    -                    if (!snapshotTaken) { // true for the pre v1.0 case
    -                       zk.takeSnapshot();
    +                    if (isPreZAB1_0) {
    +                        zk.takeSnapshot();
                             self.setCurrentEpoch(newEpoch);
                         }
                         self.setZooKeeperServer(zk);
                         self.adminServer.setZooKeeperServer(zk);
                         break outerLoop;
    -                case Leader.NEWLEADER: // it will be NEWLEADER in v1.0        
    +                case Leader.NEWLEADER: // Getting NEWLEADER here instead of in discovery 
    +                    // means this is Zab 1.0
    +                    // Create updatingEpoch file and remove it after current
    --- End diff --
    
    You are right will fix that.


> 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
>
> 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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