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https://issues.apache.org/jira/browse/HADOOP-15625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16778532#comment-16778532
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Ben Roling commented on HADOOP-15625:
-------------------------------------

bq. which means that you may open an object and it has a null version -but the 
bucket itself is still versioned. We may not want to give up completely in this 
world

Yeah, that should be noted in the documentation about the "require version" 
configuration.  You shouldn't use that unless you can be confident all your 
buckets will have versioning enabled from the beginning.

> 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
>
>
> 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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