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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2846) Leader follower sync with on disk txns can possibly leads to data inconsistency
Date Tue, 18 Jul 2017 19:38:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16092059#comment-16092059

ASF GitHub Bot commented on ZOOKEEPER-2846:

GitHub user lvfangmin opened a pull request:


    [ZOOKEEPER-2846][Test] Leader follower sync with on disk txns can possibly leads to data

    This is only the test case used to reproduce the issue.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/lvfangmin/zookeeper ZOOKEEPER-2846-TEST

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #314
commit c2a1ec8f989b9f799f5880a92730b75ef86164b9
Author: Fangmin Lyu <allenlyu@fb.com>
Date:   2017-07-18T19:21:02Z

    add test case to check data inconsistency issue when using on-disk txn sync


> Leader follower sync with on disk txns can possibly leads to data inconsistency
> -------------------------------------------------------------------------------
>                 Key: ZOOKEEPER-2846
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2846
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: quorum
>    Affects Versions: 3.4.10, 3.5.3, 3.6.0
>            Reporter: Fangmin Lv
>            Priority: Critical
> On disk txn sync could cause data inconsistency if the current leader just had a snap
sync before it became leader, and then having diff sync with its followers may synced the
txns gap on disk. Here is scenario: 
> Let's say S0 - S3 are followers, and S4 is leader at the beginning:
> 1. Stop S2 and send one more request
> 2. Stop S3 and send more requests to the quorum to let S3 have a snap sync with S4 when
it started up
> 3. Stop S4 and S3 became the new leader
> 4. Start S2 and had a diff sync with S3, now there are gaps in S2
> Attached the test case to verify the issue. Currently, there is no efficient way to check
the gap in txn files is a real gap or due to Epoch change. We need to add that support, but
before that, it would be safer to disable the on disk txn leader-follower sync.

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