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https://issues.apache.org/jira/browse/HDFS-2949?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kihwal Lee updated HDFS-2949:
-----------------------------

       Resolution: Fixed
    Fix Version/s: 2.5.0
                   3.0.0
     Hadoop Flags: Reviewed
           Status: Resolved  (was: Patch Available)

I've committed this to branch-2 and trunk. Thanks for working on the fix, 
Rushabh.

> HA: Add check to active state transition to prevent operator-induced split 
> brain
> --------------------------------------------------------------------------------
>
>                 Key: HDFS-2949
>                 URL: https://issues.apache.org/jira/browse/HDFS-2949
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ha, namenode
>    Affects Versions: 0.24.0
>            Reporter: Todd Lipcon
>            Assignee: Rushabh S Shah
>             Fix For: 3.0.0, 2.5.0
>
>         Attachments: HDFS-2949-v2.patch, HDFS-2949-v3.patch, HDFS-2949.patch
>
>
> Currently, if the administrator mistakenly calls "-transitionToActive" on one 
> NN while the other one is still active, all hell will break loose. We can add 
> a simple check by having the NN make a getServiceState() RPC to its peer with 
> a short (~1 second?) timeout. If the RPC succeeds and indicates the other 
> node is active, it should refuse to enter active mode. If the RPC fails or 
> indicates standby, it can proceed.
> This is just meant as a preventative safety check - we still expect users to 
> use the "-failover" command which has other checks plus fencing built in.



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