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From "suja s (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-3161) 20 Append: Excluded DN replica from recovery should be removed from DN.
Date Thu, 29 Mar 2012 08:52:30 GMT
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
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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