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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1144) ZooKeeperServer not starting on leader due to a race condition
Date Thu, 11 Aug 2011 03:23:27 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082880#comment-13082880
] 

Hadoop QA commented on ZOOKEEPER-1144:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12489635/ZOOKEEPER-1144.patch
  against trunk revision 1152141.

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

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    +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 1.3.9) warnings.

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

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

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

Test results: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/437//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/437//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/437//console

This message is automatically generated.

> ZooKeeperServer not starting on leader due to a race condition
> --------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1144
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1144
>             Project: ZooKeeper
>          Issue Type: Bug
>    Affects Versions: 3.4.0
>            Reporter: Vishal Kher
>            Assignee: Vishal Kher
>            Priority: Blocker
>             Fix For: 3.4.0
>
>         Attachments: ZOOKEEPER-1144.patch
>
>
> I have found one problem that is causing QuorumPeerMainTest:testQuorum to fail. This
test uses 2 ZK servers. 
> The test is failing because leader is not starting ZooKeeperServer after leader election.
so everything halts.
> With the new changes, the server is now started in Leader.processAck() which is called
from LeaderHandler. processAck() starts ZooKeeperServer if majority have acked NEWLEADER.
The leader puts its ack in the the ackSet in Leader.lead(). Since processAck() is called from
LearnerHandler it can happen that the learner's ack is processed before the leader is able
to put its ack in the ackSet. When LearnerHandler invokes processAck(), the ackSet for newLeaderProposal
will not have quorum (in this case 2). As a result, the ZooKeeperServer is never started on
the Leader.
> The leader needs to ensure that its ack is put in ackSet before starting LearnerCnxAcceptor
or invoke processAck() itself after adding to ackSet. I haven't had time to go through the
ZAB2 changes so I am not too familiar with the code. Can Ben/Flavio fix this?

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