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From "Daryn Sharp (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7771) NPE when running hdfs dfs -copyToLocal, -get etc
Date Thu, 15 Mar 2012 14:15:37 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13230188#comment-13230188
] 

Daryn Sharp commented on HADOOP-7771:
-------------------------------------

Yes, I wouldn't expect users to know or care about temp files.  I don't recall which of all
the copy variants already had this behavior but I standardized it across the copy commands.
 Distcp has similar behavior, although I think it copies into a temp subdir.  Maybe it would
make sense to mimic what it does?

It's true that users could read the partial files, but I question if users would expect a
partial file in the vast majority of use cases.  Let's say a copy failed, the user didn't
check the exit code possibly because 20x exit codes were unreliable, and then attempted to
run a job.  The job might "succeed" to process the partial data but produce erroneous results.
 Users might be baffled that re-running the job produces different results.  A dev may go
on a wild goose chase and resolve as "works for me" when they can't reproduce.

If the client is interrupted by a signal, then it often used to leave a temp file because
the signal wasn't breaking out correctly and affecting the shutdown hooks.  I recently fixed
that.  I've been meaning to investigation/reproduce/fix a few user reports that temp files
are still sometimes left around.  If you do a hard kill (-9), then of course there's nothing
that can be done unless the NN has a notion of this "this file should be deleted unless I
explicitly close it".

What are your thoughts?
                
> NPE when running hdfs dfs -copyToLocal, -get etc
> ------------------------------------------------
>
>                 Key: HADOOP-7771
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7771
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 0.23.0, 0.24.0
>            Reporter: John George
>            Assignee: John George
>            Priority: Blocker
>             Fix For: 0.23.0, 0.24.0
>
>         Attachments: HADOOP-7771.patch, HADOOP-7771.patch, HADOOP-7771.patch, HADOOP-7771.patch,
HADOOP-7771.patch, HADOOP-7771.patch
>
>
> NPE when running hdfs dfs -copyToLocal if the destination directory does not exist. The
behavior in branch-0.20-security is to create the directory and copy/get the contents from
source.

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