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https://issues.apache.org/jira/browse/HADOOP-5027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12664355#action_12664355
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szetszwo edited comment on HADOOP-5027 at 1/15/09 5:34 PM:
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> May be the problem is not with the block report, but rather with 
> nextGenerationStamp(Block), ...

nextGenerationStamp(Block) should not update the block information in the 
NameNode since *the update may fail*.  If the NameNode block gs is updated but 
the DataNode block gs is not and the update fails, the the block in the 
DataNode will be considered as invalid.

> I also would like to see a unit test catching this bug.

Sure, working on one.

      was (Author: szetszwo):
    > May be the problem is not with the block report, but rather with 
nextGenerationStamp(Block), ...

nextGenerationStamp(Block) should not update the block information in the 
NameNode since *the update may fail*.  If the NameNode block gs is updated but 
the DataNode block gs is not and the update fails.  The the block in the 
DataNode will be consider as invalid.

> I also would like to see a unit test catching this bug.

Sure, working on one.
  
> Block report processing should compare gneration stamp
> ------------------------------------------------------
>
>                 Key: HADOOP-5027
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5027
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>             Fix For: 0.19.1
>
>         Attachments: 5027_20090114.patch
>
>
> If a reported block has a different generation stamp then the one stored in 
> the NameNode, the reported block will be considered as invalid.  This is 
> incorrect since blocks with larger generation stamp are valid.

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