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https://issues.apache.org/jira/browse/HADOOP-6304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12983960#action_12983960
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Todd Lipcon commented on HADOOP-6304:
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Hey Arun. MAPREDUCE-2238 was caused by the use of these same APIs in
Localizer.PermissionsHandler.setPermissions. What was happening was something
like the following:
- Thread A: setPermissions("/path/to/userlogs", 755)
- Thread B: setPermissions("/path/to/userlogs/attempt_x", 755)
The way they got interleaved was something like:
- B: set userlogs/attempt_x to 000
- A: set userlogs/ to 000
- B: try to restore permissions on attempt_x, but fail since it can't traverse
the path
- A: set userlogs/ back to 755
- The attempt_x directory is left at 000 or some other "incomplete" permissions
where any following Hudson runs won't be able to delete it.
This same problem can happen in a real cluster too.
So I think the pattern used in this patch (same as the one in
Localizer.PermissionsHandler.setPermissions) is dangerous because it's not
atomic. This was just one manifestation of the issue.
I agree JNI is difficult but this is a very simple use of it. No buffer
management, no complicated errors to handle, no strange system APIs. Let's have
the JNI discussion over in HADOOP-7110 though.
> Use java.io.File.set{Readable|Writable|Executable} where possible in
> RawLocalFileSystem
> ----------------------------------------------------------------------------------------
>
> Key: HADOOP-6304
> URL: https://issues.apache.org/jira/browse/HADOOP-6304
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs
> Affects Versions: 0.20.1
> Reporter: Arun C Murthy
> Assignee: Arun C Murthy
> Attachments: HADOOP-6304_yhadoop20.patch
>
>
> Using java.io.File.set{Readable|Writable|Executable} where possible in
> RawLocalFileSystem when g & o perms are same saves a lot of 'fork'
> system-calls.
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