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https://issues.apache.org/jira/browse/HADOOP-15297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16390281#comment-16390281
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Steve Loughran commented on HADOOP-15297:
-----------------------------------------
HADOOP-15297 patch 001
* make etag feature optional, disabled by default
* update tests to check both states
* update docs
* also update instrumentation to track invocations. Not directly used, but
useful for anything downstream trying to track the #of calls made
Testing: S3 ireland, also did the mvn site:site to verify the updated docs were
valid.
> Make s3a etag -> checksum publishing option
> -------------------------------------------
>
> Key: HADOOP-15297
> URL: https://issues.apache.org/jira/browse/HADOOP-15297
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.1.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Blocker
> Attachments: HADOOP-15297-001.patchh
>
>
> HADOOP-15273 shows how distcp doesn't handle non-HDFS filesystems with
> checksums.
> Exposing Etags as checksums, HADOOP-13282, breaks workflows which back up to
> s3a.
> Rather than revert I want to make it an option, off by default. Once we are
> happy with distcp in future, we can turn it on.
> Why an option? Because it lines up for a successor to distcp which saves src
> and dest checksums to a file and can then verify whether or not files have
> really changed. Currently distcp relies on dest checksum algorithm being the
> same as the src for incremental updates, but if either of the stores don't
> serve checksums, silently downgrades to not checking.
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