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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-321) DatanodeInfo refactoring
Date Wed, 28 Jun 2006 05:14:30 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-321?page=comments#action_12418168 ] 

Owen O'Malley commented on HADOOP-321:
--------------------------------------

This is the patch that broke the system. Having looked at this code, I don't like the use
of inheritance between DatanodeInfo and DatanodeDescriptor. I think that composition is a
_much_ better approach. They are _not_ logically the sub/super-type of each other. In particular,
DatanodeInfo is intended to be Writable and DatanodeDescriptor is intended NOT to be Writable.
Making them inherit from each other not only broke the system, it is a really problematic
design.

In any case, if you take svn head and revert this patch using:
patch -p0 -R < DatanodeRefactor.patch
you'll have a working system again.

> DatanodeInfo refactoring
> ------------------------
>
>          Key: HADOOP-321
>          URL: http://issues.apache.org/jira/browse/HADOOP-321
>      Project: Hadoop
>         Type: Improvement

>   Components: dfs
>     Reporter: Konstantin Shvachko
>      Fix For: 0.4.0
>  Attachments: DatanodeInfo_refactor.patch
>
> I'm trying to refactor some name node classes, which seem to be similar.
> So DatanodeInfo is a public api now for purely external ( to name node) use.
> The name node class that stores information about data nodes including the
> set of its blocks is called DatanodeDescriptor.
> The DatanodeReport is removed since it was a variation of DatanodeInfo.
> Previously DatanodeInfo and DatanodeDescriptor were the same class, and
> DatanodeReport was used for reporting node statistics only.
> This is a preparation step for HADOOP-306.

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