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https://issues.apache.org/jira/browse/HDFS-644?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12759803#action_12759803
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Konstantin Boudnik commented on HDFS-644:
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Bummer... Yes, you're right of course

> Lease recovery, concurrency support.
> ------------------------------------
>
>                 Key: HDFS-644
>                 URL: https://issues.apache.org/jira/browse/HDFS-644
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: data-node, hdfs client, name-node
>    Affects Versions: Append Branch
>            Reporter: Konstantin Shvachko
>            Assignee: Konstantin Shvachko
>             Fix For: Append Branch
>
>         Attachments: leaseRecovery.patch
>
>
> Lease recovery happens if hdfs client does not renew its leases within an 
> hour. Lease recovery triggers block recovery if the block has not been 
> completed during normal write or append operations. Name-node initiates such 
> block recovery by sending BlockRecoveryCommand to data-nodes (via reply to a 
> heartbeat). There could be a race condition if some data-nodes still recover 
> the block when the name-node decides to start a new recovery because the 
> previous one did not complete. This issue should take of the race condition 
> by introducing recovery ids. It should also implement the new recovery 
> protocol, which is described in the append design document,

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