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https://issues.apache.org/jira/browse/HADOOP-5133?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12668096#action_12668096
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Konstantin Shvachko commented on HADOOP-5133:
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I do not think name-node's decision on whether the block is corrupt or not
should be based on its length. This assumes that files can only grow. If we
ever decide to implement truncates, which is a reasonable extension of append,
this whole logic will have to be reconsidered.
I think the decision should rather be based on generation stamps, etc.
> FSNameSystem#addStoredBlock does not handle inconsistent block length
> correctly
> -------------------------------------------------------------------------------
>
> Key: HADOOP-5133
> URL: https://issues.apache.org/jira/browse/HADOOP-5133
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.18.2
> Reporter: Hairong Kuang
> Fix For: 0.19.1
>
>
> Currently NameNode treats either the new replica or existing replicas as
> corrupt if the new replica's length is inconsistent with NN recorded block
> length. The correct behavior should be
> 1. For a block that is not under construction, the new replica should be
> marked as corrupt if its length is inconsistent (no matter shorter or longer)
> with the NN recorded block length;
> 2. For an under construction block, if the new replica's length is shorter
> than the NN recorded block length, the new replica could be marked as
> corrupt; if the new replica's length is longer, NN should update its recorded
> block length. But it should not mark existing replicas as corrupt. This is
> because NN recorded length for an under construction block does not
> accurately match the block length on datanode disk. NN should not judge an
> under construction replica to be corrupt by looking at the inaccurate
> information: its recorded block length.
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