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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2953) Flaky Test: testNoLogBeforeLeaderEstablishment
Date Thu, 14 Dec 2017 17:27:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2953?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16291213#comment-16291213

Hadoop QA commented on ZOOKEEPER-2953:

-1 overall.  GitHub Pull Request  Build

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 9 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 3.0.1) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/1373//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/1373//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://builds.apache.org/job/PreCommit-ZOOKEEPER-github-pr-build/1373//console

This message is automatically generated.

> Flaky Test: testNoLogBeforeLeaderEstablishment
> ----------------------------------------------
>                 Key: ZOOKEEPER-2953
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2953
>             Project: ZooKeeper
>          Issue Type: Bug
>    Affects Versions: 3.5.3, 3.4.11, 3.6.0
>            Reporter: Abraham Fine
>            Assignee: Abraham Fine
> testNoLogBeforeLeaderEstablishment has been flaky on 3.4, 3.5, and master for quite awhile.
My understanding is that the purpose of the test is to make sure that a server receives support
from the quorum before changing the epoch and acting as leader. 
> There are a couple issues with the test in its current state. First, the assertions the
test makes are not always true. It is possible, if the zookeeper database is not cleared,
for a follower to be ahead of a leader when the quorum is shutdown. That follower will then
likely become leader when the quorum is restarted. This is the cause of the flaky behavior.
Second, the test does not appear to create the conditions it wants to test for. Since, ZOOKEEPER-335
(specifically the ZOOKEEPER-1081 subtask) we take the epoch into consideration in {{FastLeaderElection}}
so the test no longer "believes it is the leader once it recovers".
> After discussing the issue offline with [~phunt] we decided it would still be valuable
to test the situation where a server is elected leader without the support of the quorum.
So I removed {{testNoLogBeforeLeaderEstablishment}} and created a new test called {{testElectionFraud}}.

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