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https://issues.apache.org/jira/browse/MAPREDUCE-1519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12836514#action_12836514
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Rodrigo Schmidt commented on MAPREDUCE-1519:
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Sure, Dhruba!
Let's assume there's a file /usr/schmidt/file1 that has been recently raided.
In that case, the RaidNode will have crated a parity file
/raid/usr/schmidt/file1
Now, imagine the user rewrites its original file and creates a new version of
/usr/schmidt/file1.
The RaidNode correctly identifies the file has to be re-raided, creates the
parity file in a temporary directory, but when it tries to move the newly
created parity file from the temporary directory to /raid/usr/schmidt/file1, it
fails because the destination already exists.
The patch verifies if the destination exists before renaming it and deletes the
file in that case.
The unit test covers this scenario.
I actually found this bug when you proposed to add the unit test that covers
this scenario on my patch to MAPREDUCE-1510. I didn't want to fix this bug
there because (i) MAPREDUCE-1510 was an improvement and not a bug, and (ii)
neither the title or the description of MAPREDUCE-1510 covers this failure
scenario and people looking for this problem would have a hard time finding the
correct JIRA.
> RaidNode fails to create new parity file if an older version already exists
> ---------------------------------------------------------------------------
>
> Key: MAPREDUCE-1519
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1519
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: contrib/raid
> Reporter: Rodrigo Schmidt
> Assignee: Rodrigo Schmidt
> Attachments: MAPREDUCE-1519.patch
>
>
> When RaidNode tries to recreate a parity file for a source file that has been
> modified (recreated) recently, it crashes.
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