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From "Uma Maheswara Rao G (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3161) 20 Append: Excluded DN replica from recovery should be removed from DN.
Date Thu, 29 Mar 2012 09:12:31 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13241095#comment-13241095
] 

Uma Maheswara Rao G commented on HDFS-3161:
-------------------------------------------

Thanks a lot Suja for reporting the issue.

                
> 20 Append: Excluded DN replica from recovery should be removed from DN.
> -----------------------------------------------------------------------
>
>                 Key: HDFS-3161
>                 URL: https://issues.apache.org/jira/browse/HDFS-3161
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 1.0.0
>            Reporter: suja s
>            Priority: Critical
>             Fix For: 1.0.3
>
>
> 1) DN1->DN2->DN3 are in pipeline.
> 2) Client killed abruptly
> 3) one DN has restarted , say DN3
> 4) In DN3 info.wasRecoveredOnStartup() will be true
> 5) NN recovery triggered, DN3 skipped from recovery due to above check.
> 6) Now DN1, DN2 has blocks with generataion stamp 2 and DN3 has older generation stamp
say 1 and also DN3 still has this block entry in ongoingCreates
> 7) as part of recovery file has closed and got only two live replicas ( from DN1 and
DN2)
> 8) So, NN issued the command for replication. Now DN3 also has the replica with newer
generation stamp.
> 9) Now DN3 contains 2 replicas on disk. and one entry in ongoing creates with referring
to blocksBeingWritten directory.
> When we call append/ leaseRecovery, it may again skip this node for that recovery as
blockId entry still presents in ongoingCreates with startup recovery true.
> It may keep continue this dance for evry recovery.
> And this stale replica will not be cleaned untill we restart the cluster. Actual replica
will be trasferred to this node only through replication process.
> Also unnecessarily that replicated blocks will get invalidated after next recoveries....

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