[jira] [Created] (HDFS-2949) HA: Add check to active state transition to prevent operator-induced split brain

["Todd Lipcon (Created) (JIRA)" <ji...@apache.org>]

HA: Add check to active state transition to prevent operator-induced split brain
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                 Key: HDFS-2949
                 URL: https://issues.apache.org/jira/browse/HDFS-2949
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: ha, name-node
    Affects Versions: HA branch (HDFS-1623)
            Reporter: Todd Lipcon


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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