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https://issues.apache.org/jira/browse/HADOOP-3310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598020#action_12598020
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Tsz Wo (Nicholas), SZE commented on HADOOP-3310:
------------------------------------------------

>how to tells whether a block is being updated?

When updating a block, the meta file is renamed to a tmp file at first.  After 
the update is done, the tmp file will be renamed to the new meta file (with the 
new generation stamp.)  It should work.

> Lease recovery for append
> -------------------------
>
>                 Key: HADOOP-3310
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3310
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: 3310_20080514.patch, 3310_20080516b.patch, 
> 3310_20080516c.patch
>
>
> In order to support file append, a GenerationStamp is associated with each 
> block.  Lease recovery will be performed when there is a possibility that the 
> replicas of a block in a lease may have different GenerationStamp values.
> For more details, see the documentation in HADOOP-1700.

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