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Date: Mon, 26 Mar 2012 22:54:27 +0000 (UTC)
From: "Aaron T. Myers (Commented) (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-2185) HA: HDFS portion of ZK-based
 FailoverController
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    [ https://issues.apache.org/jira/browse/HDFS-2185?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13238942#comment-13238942 ] 

Aaron T. Myers commented on HDFS-2185:
--------------------------------------

bq. I don't think there's a race condition here, since the NN itself always starts in standby mode, and the minicluster startup waits until it is fully active.

Ah, I thought that MiniDFSCluster might return from waitActive while still in the INITIALIZING state. My mistake. I agree with you, then, that there's no race condition.

Latest patch looks good to me. +1 pending Jenkins and the commit of the Common patch.
                
> HA: HDFS portion of ZK-based FailoverController
> -----------------------------------------------
>
>                 Key: HDFS-2185
>                 URL: https://issues.apache.org/jira/browse/HDFS-2185
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha
>    Affects Versions: HA branch (HDFS-1623)
>            Reporter: Eli Collins
>            Assignee: Todd Lipcon
>         Attachments: Failover_Controller.jpg, hdfs-2185.txt, hdfs-2185.txt, hdfs-2185.txt, zkfc-design.pdf
>
>
> This jira is for a ZK-based FailoverController daemon. The FailoverController is a separate daemon from the NN that does the following:
> * Initiates leader election (via ZK) when necessary
> * Performs health monitoring (aka failure detection)
> * Performs fail-over (standby to active and active to standby transitions)
> * Heartbeats to ensure the liveness
> It should have the same/similar interface as the Linux HA RM to aid pluggability.

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