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From "Hudson (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 Tue, 10 Feb 2015 11:37:29 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14314046#comment-14314046
] 

Hudson commented on HDFS-7714:
------------------------------

FAILURE: Integrated in Hadoop-Yarn-trunk #834 (See [https://builds.apache.org/job/Hadoop-Yarn-trunk/834/])
HDFS-7714. Simultaneous restart of HA NameNodes and DataNode can cause DataNode to register
successfully with only one NameNode.(Contributed by Vinayakumar B) (vinayakumarb: rev 3d15728ff5301296801e541d9b23bd1687c4adad)
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt


> 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
>             Fix For: 2.7.0
>
>         Attachments: HDFS-7714-001.patch, HDFS-7714-002.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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