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https://issues.apache.org/jira/browse/MAPREDUCE-4987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13574097#comment-13574097
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Ivan Mitic commented on MAPREDUCE-4987:
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Thanks for reporting this Chris.
bq. But symlinks CAN be used for functional purposes i.e linking to libraries
etc. ?
Hi Vinod. I believe we'll have to port the branch-1-win semantic to trunk to
properly support symlinks on both Java6 and Java7 on Windows. Yes, symlinks can
be created to point to folders and files, however, Java6 does not interpret
them correctly. We've seen so many issues with symlinks on Java6, and the only
option that worked fine (and was signed off on) is to do a file copy in case of
Java6. HADOOP-9061 talks about some of these problems.
bq. If so we can just do the platform check in the test-case.
We also initially thought this would be fine (you can check thru branch-1-win
history :)). However, the real problem comes when someone tries to access the
symlink thru Java APIs. Examples of problems are, File#length on symlinks
returns zero. This means that RLFS does not work on top of symlinks.
Additionally, File#renameTo on symlink renames the target file instead of the
symlink (really strange I know :)).
Hope this helps
> TestMRJobs#testDistributedCache fails on Windows due to unexpected behavior
> of symlinks
> ---------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4987
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4987
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: distributed-cache, nodemanager
> Affects Versions: trunk-win
> Reporter: Chris Nauroth
>
> On Windows, {{TestMRJobs#testDistributedCache}} fails on an assertion while
> checking the length of a symlink. It expects to see the length of the target
> of the symlink, but Java 6 on Windows always reports that a symlink has
> length 0.
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