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From "Tsz Wo (Nicholas), SZE (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3050) rework OEV to share more code with the NameNode
Date Fri, 30 Mar 2012 21:13:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242751#comment-13242751

Tsz Wo (Nicholas), SZE commented on HDFS-3050:

> The offline edits viewer has @InterfaceAudience.Private, @InterfaceStability.Unstable.
There are no proposals (as far as I know) to change that.

You are right.
> rework OEV to share more code with the NameNode
> -----------------------------------------------
>                 Key: HDFS-3050
>                 URL: https://issues.apache.org/jira/browse/HDFS-3050
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HDFS-3050.006.patch, HDFS-3050.007.patch, HDFS-3050.008.patch, HDFS-3050.009.patch,
HDFS-3050.010.patch, HDFS-3050.011.patch, HDFS-3050.012.patch, HDFS-3050.014.patch, HDFS-3050.015.patch,
> Current, OEV (the offline edits viewer) re-implements all of the opcode parsing logic
found in the NameNode.  This duplicated code creates a maintenance burden for us.
> OEV should be refactored to simply use the normal EditLog parsing code, rather than rolling
its own.  By using the existing FSEditLogLoader code to load edits in OEV, we can avoid having
to update two places when the format changes.
> We should not put opcode checksums into the XML, because they are a serialization detail,
not related to what the data is what we're storing.  This will also make it possible to modify
the XML file and translate this modified file back to a binary edits log file.
> Finally, this changes introduces --fix-txids.  When OEV is passed this flag, it will
close gaps in the transaction log by modifying the sequence numbers.  This is useful if you
want to modify the edit log XML (say, by removing a transaction), and transform the modified
XML back into a valid binary edit log file.

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