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Date: Wed, 19 Dec 2012 08:53:15 +0000 (UTC)
From: "Li Junjun (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12556631.1337570881513.28890.1355907195614@arcas>
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Subject: [jira] [Commented] (HDFS-3448) CLONE - Why open method in class
 DFSClient would compare old LocatedBlocks and new LocatedBlocks?
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    [ https://issues.apache.org/jira/browse/HDFS-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13535787#comment-13535787 ] 

Li Junjun commented on HDFS-3448:
---------------------------------

Sorry,i'm  be familiar with  jira and svn
                
> CLONE - Why open method in class DFSClient would compare old LocatedBlocks and new LocatedBlocks?
> -------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3448
>                 URL: https://issues.apache.org/jira/browse/HDFS-3448
>             Project: Hadoop HDFS
>          Issue Type: Wish
>          Components: hdfs-client
>    Affects Versions: 1.0.1
>            Reporter: Li Junjun
>            Assignee: Todd Lipcon
>   Original Estimate: 168h
>  Remaining Estimate: 168h
>
>  I think there are two situations.
> 1,the file has been swapped with another file,we check the blockId,that's correct we throw Exceptions!
> 2,but if the file has not been swapped but has been appended ,we should just check the blockId ,and should not care about the block's stamp , because in fact we got the right and updated block list , cause file in hdfs can't be truncate .
> so how about we do it like this ?
> if ( oldIter.next().getBlock().getBlockId() != newIter.next().getBlock().getBlockId() ) { throw new IOException("Blocklist for " + src + " has changed!"); }
> after all , between two calls to openInfo() the file can be swapped and then appending,so we should not ignore the under construction file.

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