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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2791) If block report races with closing of file, replica is incorrectly marked corrupt
Date Wed, 25 Jan 2012 01:46:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2791?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13192778#comment-13192778
] 

Todd Lipcon commented on HDFS-2791:
-----------------------------------

>> Case 2) if the block has the correct generation stamp, ignore it (don't add to block
locations or mark it corrupt)
> This looks ok at first sight. If the generation stamp and length matches with what the
NN has is it safe to add it to the blocksmap?

Yes, I think so. I had originally thought about doing that, but ATM convinced me otherwise
- our thinking is now that this case only occurs because of a temporary delay in transmission
of the "correct" state. So we'll always expect to see the FINALIZED report come in soon after
one of these RBW replicas. Given that, I think it is simpler/safer to ignore it in all cases.
                
> If block report races with closing of file, replica is incorrectly marked corrupt
> ---------------------------------------------------------------------------------
>
>                 Key: HDFS-2791
>                 URL: https://issues.apache.org/jira/browse/HDFS-2791
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node, name-node
>    Affects Versions: 0.22.0, 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hdfs-2791-test.txt, hdfs-2791.txt, hdfs-2791.txt, hdfs-2791.txt
>
>
> The following sequence of events results in a replica mistakenly marked corrupt:
> 1. Pipeline is open with 2 replicas
> 2. DN1 generates a block report but is slow in sending to the NN (eg some flaky network).
It gets "stuck" right before the block report RPC.
> 3. Client closes the file.
> 4. DN2 is fast and sends blockReceived to the NN. NN marks the block as COMPLETE
> 5. DN1's block report proceeds, and includes the block in an RBW state.
> 6. (x) NN incorrectly marks the replica as corrupt, since it is an RBW replica on a COMPLETE
block.

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