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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (HADOOP-3310) Lease recovery for append
Date Tue, 13 May 2008 23:11:57 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3310?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12594365#action_12594365
] 

szetszwo edited comment on HADOOP-3310 at 5/13/08 4:10 PM:
-------------------------------------------------------------------------

*Lease Recovery Algorithm*
{code}
  /*
   * 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 contains b
   * 2.2) Assign one of the datanodes as the primary datanode p

   * 2.3) p obtains a new generation stamp form the namenode
   * 2.4) p get the block info from each datanode
   * 2.5) p computes the minimum block length
   * 2.6) p updates the datanodes, which have a valid generation stamp,
   *      with the new generation stamp and the minimum block length 
   * 2.7) p acknowledges the namenode the update results

   * 2.8) Namenode updates the BlockInfo
   * 2.9) Namenode removes f from the lease
   *      and removes the lease once all files have been removed
   * 2.10) Namenode commit changes to edit log
   */
{code}


      was (Author: szetszwo):
    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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