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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4288) NN accepts incremental BR as IBR in safemode
Date Sun, 23 Dec 2012 14:52:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13539034#comment-13539034
] 

Suresh Srinivas commented on HDFS-4288:
---------------------------------------

Thinking about the problem a bit, what we need is a way to indicate if this is the first block
report from datanode itself. So adding a counter starting with 0 (to indicate first block
report) in block reports from datanode to namenode should help solve the problem. With this
we can get rid of the DatanodeDescriptor#firstBlockReport and related code. This will also
solve issues related to DN restart and NN may not process the block report.

                
> NN accepts incremental BR as IBR in safemode
> --------------------------------------------
>
>                 Key: HDFS-4288
>                 URL: https://issues.apache.org/jira/browse/HDFS-4288
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 0.23.0, 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>         Attachments: HDFS-4288.branch-23.patch
>
>
> If a DN is ready to send an incremental BR and the NN goes down, the DN will repeatedly
try to reconnect.  The NN will then process the DN's incremental BR as an initial BR.  The
NN now thinks the DN has only a few blocks, and will ignore all subsequent BRs from that DN
until out of safemode -- which it may never do because of all the "missing" blocks on the
affected DNs.

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