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https://issues.apache.org/jira/browse/HADOOP-16090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17068692#comment-17068692
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Andrew Olson commented on HADOOP-16090:
---------------------------------------
It seems perhaps there should be some general guidance somewhere about whether
[Object
Versioning|https://docs.aws.amazon.com/AmazonS3/latest/dev/ObjectVersioning.html]
is recommended for buckets used as S3A filesystems. I think the answer is "no,
it is strongly discouraged and may introduce unexpected performance issues or
add operational complexity" (e.g. accumulation of delete markers, deleting
files not reducing bucket storage size unless non-current removal lifecycle
policy is setup, etc). Unless there are special considerations (i.e. using
versioning as a kind of replacement for "move to trash" functionality, since
the "move to trash" performs much slower for S3A than HDFS), it would seem
generally best to not enable versioning.
[https://hadoop.apache.org/docs/current/hadoop-aws/tools/hadoop-aws/index.html]
is probably the best place if that were to happen. I don't see anywhere where
it discusses this topic deeply, with the various pros/cons evaluated.
> 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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