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https://issues.apache.org/jira/browse/MAPREDUCE-1288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12789134#action_12789134
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Devaraj Das commented on MAPREDUCE-1288:
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Look at this scenario - the URI is hdfs://<host>:<port>/foo/bar/file.txt. Even
if the entire path were accessible to everyone, the TaskTracker would localize
it exactly once, and in a user's private directory. A second job wishing to
access the same file wouldn't be able to do so since the TT wouldn't localize
it again.. Does that make sense ?
> DistributedCache localizes only once per cache URI
> --------------------------------------------------
>
> Key: MAPREDUCE-1288
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1288
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: security, tasktracker
> Affects Versions: 0.21.0
> Reporter: Devaraj Das
> Priority: Blocker
> Fix For: 0.21.0
>
>
> As part of the file localization the distributed cache localizer creates a
> copy of the file in the corresponding user's private directory. The
> localization in DistributedCache assumes the key as the URI of the cachefile
> and if it already exists in the map, the localization is not done again. This
> means that another user cannot access the same distributed cache file. We
> should change the key to include the username so that localization is done
> for every user.
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