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https://issues.apache.org/jira/browse/HADOOP-13278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17037135#comment-17037135
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Steve Loughran commented on HADOOP-13278:
-----------------------------------------
Revisiting
* If all we want to do is stop dir-under-file, we can just do a HEAD <prefix>
all the way up
* if we want to track what to delete as we go up, then we can do a HEAD + /,
but that runs a risk of creating 404 entries
* and if we optimize for a dir goes under a non-empty dir, should do a LIST
first
> S3AFileSystem mkdirs does not need to validate parent path components
> ---------------------------------------------------------------------
>
> Key: HADOOP-13278
> URL: https://issues.apache.org/jira/browse/HADOOP-13278
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs/s3, tools
> Reporter: Adrian Petrescu
> Priority: Minor
>
> According to S3 semantics, there is no conflict if a bucket contains a key
> named {{a/b}} and also a directory named {{a/b/c}}. "Directories" in S3 are,
> after all, nothing but prefixes.
> However, the {{mkdirs}} call in {{S3AFileSystem}} does go out of its way to
> traverse every parent path component for the directory it's trying to create,
> making sure there's no file with that name. This is suboptimal for three main
> reasons:
> * Wasted API calls, since the client is getting metadata for each path
> component
> * This can cause *major* problems with buckets whose permissions are being
> managed by IAM, where access may not be granted to the root bucket, but only
> to some prefix. When you call {{mkdirs}}, even on a prefix that you have
> access to, the traversal up the path will cause you to eventually hit the
> root bucket, which will fail with a 403 - even though the directory creation
> call would have succeeded.
> * Some people might actually have a file that matches some other file's
> prefix... I can't see why they would want to do that, but it's not against
> S3's rules.
> I've opened a pull request with a simple patch that just removes this portion
> of the check. I have tested it with my team's instance of Spark + Luigi, and
> can confirm it works, and resolves the aforementioned permissions issue for a
> bucket on which we only had prefix access.
> This is my first ticket/pull request against Hadoop, so let me know if I'm
> not following some convention properly :)
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