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Date: Mon, 5 May 2008 15:17:55 -0700 (PDT)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Updated: (HADOOP-3310) Lease recovery for append
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     [ https://issues.apache.org/jira/browse/HADOOP-3310?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tsz Wo (Nicholas), SZE updated HADOOP-3310:
-------------------------------------------

    Assignee: Tsz Wo (Nicholas), SZE

The lease recovery algorithm is:
 * 1) Namenode retrieves lease information
 * 2) For each file f in the lease, consider the last block b of f
 * 2.1) Get the datanodes which containing b
 * 2.2) Assign one of the datanodes as the primary datanode p
 * 2.3) p checks with all the datanodes,
 *      see whether block synchronization is required.
 * 2.4) If synchronization is required
 * 2.4.1) obtain a new generation stamp form the namenode
 * 2.4.2) compute the minimum block length (this is the synchronized length)
 * 2.4.3) update all datanodess (each datanode update its block file)
 * 2.4.4) acknowledge the namenode.
 * 2.5) Namenode commit the new generation stamp 
 * 2.6) Namenode removes f (and update INode) from the lease
 * 3) Namenode removes the lease once all files have been removed.  


> 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
>
> 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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