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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7714) Simultaneous restart of HA NameNodes and DataNode can cause DataNode to register successfully with only one NameNode.
Date Fri, 06 Feb 2015 22:31:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14310060#comment-14310060
] 

Chris Nauroth commented on HDFS-7714:
-------------------------------------

Thank you for taking this issue, Vinay.  I think catching {{EOFException}} is a fine approach.
 Changing the {{isAlive}} logic has some other side effects, and I believe that's what caused
the test failures in the last Jenkins run.

> Simultaneous restart of HA NameNodes and DataNode can cause DataNode to register successfully
with only one NameNode.
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-7714
>                 URL: https://issues.apache.org/jira/browse/HDFS-7714
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.6.0
>            Reporter: Chris Nauroth
>            Assignee: Vinayakumar B
>         Attachments: HDFS-7714-001.patch
>
>
> In an HA deployment, DataNodes must register with both NameNodes and send periodic heartbeats
and block reports to both.  However, if NameNodes and DataNodes are restarted simultaneously,
then this can trigger a race condition in registration.  The end result is that the {{BPServiceActor}}
for one NameNode terminates, but the {{BPServiceActor}} for the other NameNode remains alive.
 The DataNode process is then in a "half-alive" state where it only heartbeats and sends block
reports to one of the NameNodes.  This could cause a loss of storage capacity after an HA
failover.  The DataNode process would have to be restarted to resolve this.



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