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From "Patrick Hunt (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ZOOKEEPER-335) zookeeper servers should commit the new leader txn to their logs.
Date Mon, 21 Jun 2010 18:03:25 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12880917#action_12880917
] 

Patrick Hunt commented on ZOOKEEPER-335:
----------------------------------------

vishal comment on list:


I might be wrong here, but let me try to chip in my few cents.

I think the problem is in LearnerHandler.java at the leader fo this
Follower.

            /* see what other packets from the proposal
             * and tobeapplied queues need to be sent
             * and then decide if we can just send a DIFF
             * or we actually need to send the whole snapshot
             */
            long leaderLastZxid = leader.startForwarding(this, updates);
---> this leaderLastZxid returned is probably incorrect.
            // a special case when both the ids are the same
            if (peerLastZxid == leaderLastZxid) {
                packetToSend = Leader.DIFF;
                zxidToSend = leaderLastZxid;
            }

            QuorumPacket newLeaderQP = new QuorumPacket(Leader.NEWLEADER,
                    leaderLastZxid, null, null);
            oa.writeRecord(newLeaderQP, "packet");
            bufferedOutput.flush()


> zookeeper servers should commit the new leader txn to their logs.
> -----------------------------------------------------------------
>
>                 Key: ZOOKEEPER-335
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-335
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.1.0
>            Reporter: Mahadev konar
>            Assignee: Mahadev konar
>            Priority: Blocker
>             Fix For: 3.4.0
>
>         Attachments: zk.log.gz, zklogs.tar.gz
>
>
> currently the zookeeper followers do not commit the new leader election. This will cause
problems in a failure scenarios with a follower acking to the same leader txn id twice, which
might be two different intermittent leaders and allowing them to propose two different txn's
of the same zxid.

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