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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5741) In Datanode, update block may fail due to length inconsistency
Date Mon, 11 May 2009 17:39:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5741?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708125#action_12708125
] 

Hairong Kuang commented on HADOOP-5741:
---------------------------------------

In this case, there is no on-going writes. The problem is that data is not flushed to disk
when getBlockMetaDataInfo is called. But updateBlock flushes and closes the file. Therefore,
there is an inconsistency.

> In Datanode, update block may fail due to length inconsistency
> --------------------------------------------------------------
>
>                 Key: HADOOP-5741
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5741
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>
> When a primary datanode tries to recover a block.  It calls getBlockMetaDataInfo(..)
to obtains information like block length from each datanode.  Then, it calls updateBlock(..).
> The block length returned in getBlockMetaDataInfo(..) may be obtained from a unclosed
local block file F.   However, in updateBlock(..), it first closes F (if F is open) and then
gets the length.  These two lengths may be different.  In such case, updateBlock(..) throws
an exception.

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