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https://issues.apache.org/jira/browse/HADOOP-15625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16789679#comment-16789679
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Ben Roling commented on HADOOP-15625:
-------------------------------------

[~ste...@apache.org], [~gabor.bota] - any thoughts on the two test failures 
yetus is showing here before I try to dig in further?
 * hadoop.ha.TestZKFailoverController
 * hadoop.util.TestReadWriteDiskValidator

 

It seems like those failures are almost certainly unrelated, but I can look 
more to be sure.  The build passed back on patch 012 and the changes since then 
(Steve's in 013, 014, and my final correction in 015) were pretty light.

> S3A input stream to use etags to detect changed source files
> ------------------------------------------------------------
>
>                 Key: HADOOP-15625
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15625
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 3.2.0
>            Reporter: Brahma Reddy Battula
>            Assignee: Brahma Reddy Battula
>            Priority: Major
>         Attachments: HADOOP--15625-006.patch, HADOOP-15625-001.patch, 
> HADOOP-15625-002.patch, HADOOP-15625-003.patch, HADOOP-15625-004.patch, 
> HADOOP-15625-005.patch, HADOOP-15625-006.patch, HADOOP-15625-007.patch, 
> HADOOP-15625-008.patch, HADOOP-15625-009.patch, HADOOP-15625-010.patch, 
> HADOOP-15625-011.patch, HADOOP-15625-012.patch, HADOOP-15625-013-delta.patch, 
> HADOOP-15625-013.patch, HADOOP-15625-014.patch, HADOOP-15625-015.patch, 
> HADOOP-15625-015.patch
>
>
> S3A input stream doesn't handle changing source files any better than the 
> other cloud store connectors. Specifically: it doesn't noticed it has 
> changed, caches the length from startup, and whenever a seek triggers a new 
> GET, you may get one of: old data, new data, and even perhaps go from new 
> data to old data due to eventual consistency.
> We can't do anything to stop this, but we could detect changes by
> # caching the etag of the first HEAD/GET (we don't get that HEAD on open with 
> S3Guard, BTW)
> # on future GET requests, verify the etag of the response
> # raise an IOE if the remote file changed during the read.
> It's a more dramatic failure, but it stops changes silently corrupting things.



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