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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3448) Add some more hints of the problem when datanode and namenode don't match
Date Wed, 28 May 2008 18:33:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12600562#action_12600562
] 

Konstantin Shvachko commented on HADOOP-3448:
---------------------------------------------

This should actually never happen. Something is wrong with your build. Here is why.
DataNode.handshake() receives version information from the name-node and verifies it against
its own versions.
And the first thing that is verified is the build version. BV is reset every time you re-build
hadoop, while LAYOUT_VERSION
changes only if its is actually changed in the code. 
So, if the LAYOUT_VERSIONs are different then the build versions must be different too.
The assert you mentioned is really an assert and should not be used for diagnostic purposes.
May be the problem is somewhere else. Could you please post here the (different) layout versions
and (presumably equal) build versions.

> Add some more hints of the problem when datanode and namenode don't match
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-3448
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3448
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: documentation
>    Affects Versions: 0.18.0
>            Reporter: Steve Loughran
>            Priority: Minor
>         Attachments: hadoop-3448.patch
>
>   Original Estimate: 0.08h
>  Remaining Estimate: 0.08h
>
> When there is a mismatch between name and data mode, and you are running with -ea set,
then Datanode.handshake() bails out with an assertion  "Data-node and name-node layout versions
must be the same.";
> However, this message doesnt actually say which version numbers are at fault. A better
error message would include the version information, so pointing the finger of blame would
be easier.

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