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https://issues.apache.org/jira/browse/HADOOP-9652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13795321#comment-13795321
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Jason Lowe commented on HADOOP-9652:
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This change can cause ShuffleHandlers to become unresponsive when the cluster
is under load because {{exists}} is now a very expensive call in
RawLocalFileSystem. See MAPREDUCE-5584.
> RawLocalFs#getFileLinkStatus does not fill in the link owner and mode
> ---------------------------------------------------------------------
>
> Key: HADOOP-9652
> URL: https://issues.apache.org/jira/browse/HADOOP-9652
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Colin Patrick McCabe
> Assignee: Andrew Wang
> Fix For: 2.3.0
>
> Attachments: hadoop-9452-1.patch, hadoop-9652-2.patch,
> hadoop-9652-3.patch, hadoop-9652-4.patch, hadoop-9652-5.patch,
> hadoop-9652-6.patch
>
>
> {{RawLocalFs#getFileLinkStatus}} does not actually get the owner and mode of
> the symlink, but instead uses the owner and mode of the symlink target. If
> the target can't be found, it fills in bogus values (the empty string and
> FsPermission.getDefault) for these.
> Symlinks have an owner distinct from the owner of the target they point to,
> and getFileLinkStatus ought to expose this.
> In some operating systems, symlinks can have a permission other than 0777.
> We ought to expose this in RawLocalFilesystem and other places, although we
> don't necessarily have to support this behavior in HDFS.
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