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From "Uma Maheswara Rao G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3122) Block recovery with closeFile flag true can race with blockReport. Due to this blocks are getting marked as corrupt.
Date Mon, 02 Jul 2012 09:03:46 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13404950#comment-13404950
] 

Uma Maheswara Rao G commented on HDFS-3122:
-------------------------------------------

Hi Nicholas,

 I feel this issue is still valid after HDFS-3157 and when all blocks marked as corrupt.
Also we are seeing many race conditions with recovery and close, commitBlockSynchronization.
see HDFS-3584 and HDFS-3585 just reported by Brahma. Once it corrupts all the blocks, leter
even though DN sends with correct block, there is no use, as it already put them into corrupt.
Also there will not be any replication as there is no live replicas.

Thanks
Uma


                
> Block recovery with closeFile flag true can race with blockReport. Due to this blocks
are getting marked as corrupt.
> --------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3122
>                 URL: https://issues.apache.org/jira/browse/HDFS-3122
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node, name-node
>    Affects Versions: 0.23.0, 0.24.0
>            Reporter: Uma Maheswara Rao G
>            Assignee: Uma Maheswara Rao G
>            Priority: Critical
>         Attachments: blockCorrupt.txt
>
>
> *Block Report* can *race* with *Block Recovery* with closeFile flag true.
>  Block report generated just before block recovery at DN side and due to N/W problems,
block report got delayed to NN. 
> After this, recovery success and generation stamp modifies to new one. 
> And primary DN invokes the commitBlockSynchronization and block got updated in NN side.
Also block got marked as complete, since the closeFile flag was true. Updated with new genstamp.
> Now blockReport started processing at NN side. This particular block from RBW (when it
generated the BR at DN), and file was completed at NN side.
> Finally block will be marked as corrupt because of genstamp mismatch.
> {code}
>  case RWR:
>       if (!storedBlock.isComplete()) {
>         return null; // not corrupt
>       } else if (storedBlock.getGenerationStamp() != iblk.getGenerationStamp()) {
>         return new BlockToMarkCorrupt(storedBlock,
>             "reported " + reportedState + " replica with genstamp " +
>             iblk.getGenerationStamp() + " does not match COMPLETE block's " +
>             "genstamp in block map " + storedBlock.getGenerationStamp());
>       } else { // COMPLETE block, same genstamp
> {code}

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