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Date: Wed, 14 Mar 2012 20:14:38 +0000 (UTC)
From: "Hari Mankude (Commented) (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HADOOP-8163) Improve ActiveStandbyElector to
 provide hooks for fencing old active
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    [ https://issues.apache.org/jira/browse/HADOOP-8163?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13229574#comment-13229574 ] 

Hari Mankude commented on HADOOP-8163:
--------------------------------------

Hi Todd,

The question I had was how is the info znode creation prevented when the client does not have the ephemeral lock znode?  Is this ensured in the zk client or at the zookeeper?
                
> Improve ActiveStandbyElector to provide hooks for fencing old active
> --------------------------------------------------------------------
>
>                 Key: HADOOP-8163
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8163
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ha
>    Affects Versions: 0.24.0, 0.23.3
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hadoop-8163.txt
>
>
> When a new node becomes active in an HA setup, it may sometimes have to take fencing actions against the node that was formerly active. This JIRA extends the ActiveStandbyElector which adds an extra non-ephemeral node into the ZK directory, which acts as a second copy of the active node's information. Then, if the active loses its ZK session, the next active to be elected may easily locate the unfenced node to take the appropriate actions.

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