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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9220) Unnecessary transition to standby in ActiveStandbyElector
Date Mon, 21 Jan 2013 21:50:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13559135#comment-13559135
] 

Tom White commented on HADOOP-9220:
-----------------------------------

It's true that the elector checks for a stale ZK client, but that doesn't prevent the problem
here which is caused by i) having multiple watchers for the ZK client (due to the creation
of a new watcher in monitorLockNodeAsync), and ii) a postponed call to recheckElectability
unnecessarily forcing a new election (this call doesn't go through the watcher).
                
> Unnecessary transition to standby in ActiveStandbyElector
> ---------------------------------------------------------
>
>                 Key: HADOOP-9220
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9220
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ha
>            Reporter: Tom White
>            Assignee: Tom White
>         Attachments: HADOOP-9220.patch, HADOOP-9220.patch
>
>
> When performing a manual failover from one HA node to a second, under some circumstances
the second node will transition from standby -> active -> standby -> active. This
is with automatic failover enabled, so there is a ZK cluster doing leader election.

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