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https://issues.apache.org/jira/browse/HADOOP-16090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16795967#comment-16795967
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Steve Loughran commented on HADOOP-16090:
-----------------------------------------
BTW, in future, with a move to async operations, I could imagine that write
context doing the scan for parent dirs happening asynchronously with the file
write. Assuming the write takes less than a few seconds, and 200ms per probe,
if you have enough httpclient connections there'd be no delay at the end of the
write at all.
Some risk of multiple writes to same dir finding entries which will be deleted
anyway, so spurious tombstones created. Unless before that final bulk delete
did a getObjectMetada call on the first marker believed to exist, and, if
found, assume there's been a bulk delete already
> 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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