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https://issues.apache.org/jira/browse/HADOOP-15625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16785035#comment-16785035
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Hadoop QA commented on HADOOP-15625:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m  
0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  7s{color} 
| {color:red} HADOOP-15625 does not apply to trunk. Rebase required? Wrong 
Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HADOOP-15625 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12961260/HADOOP-15625-013-delta.patch
 |
| Console output | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/16019/console |
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> 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
>
>
> 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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