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https://issues.apache.org/jira/browse/HADOOP-16090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16795510#comment-16795510
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Dmitri Chmelev commented on HADOOP-16090:
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Steve, I have a slightly different patch that refractors getFileStatus() that
I’ve been testing with our code base. Do you mind waiting a couple of days (I
am out of the country right now)?
> S3A Client to add explicit support for versioned stores
> -------------------------------------------------------
>
> Key: HADOOP-16090
> URL: https://issues.apache.org/jira/browse/HADOOP-16090
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.8.1
> Reporter: Dmitri Chmelev
> Assignee: Steve Loughran
> Priority: Minor
>
> The fix to avoid calls to getFileStatus() for each path component in
> deleteUnnecessaryFakeDirectories() (HADOOP-13164) results in accumulation of
> delete markers in versioned S3 buckets. The above patch replaced
> getFileStatus() checks with a single batch delete request formed by
> generating all ancestor keys formed from a given path. Since the delete
> request is not checking for existence of fake directories, it will create a
> delete marker for every path component that did not exist (or was previously
> deleted). Note that issuing a DELETE request without specifying a version ID
> will always create a new delete marker, even if one already exists ([AWS S3
> Developer
> Guide|https://docs.aws.amazon.com/AmazonS3/latest/dev/RemDelMarker.html])
> Since deleteUnnecessaryFakeDirectories() is called as a callback on
> successful writes and on renames, delete markers accumulate rather quickly
> and their rate of accumulation is inversely proportional to the depth of the
> path. In other words, directories closer to the root will have more delete
> markers than the leaves.
> This behavior negatively impacts performance of getFileStatus() operation
> when it has to issue listObjects() request (especially v1) as the delete
> markers have to be examined when the request searches for first current
> non-deleted version of an object following a given prefix.
> I did a quick comparison against 3.x and the issue is still present:
> [https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java#L2947|https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java#L2947]
>
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