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https://issues.apache.org/jira/browse/HADOOP-12079?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16160711#comment-16160711
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Hadoop QA commented on HADOOP-12079:
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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  8s{color} 
| {color:red} HADOOP-12079 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-12079 |
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12739034/x-newest-optional0005.patch
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| Console output | 
https://builds.apache.org/job/PreCommit-HADOOP-Build/13223/console |
| Powered by | Apache Yetus 0.6.0-SNAPSHOT   http://yetus.apache.org |


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> Make 'X-Newest' header a configurable
> -------------------------------------
>
>                 Key: HADOOP-12079
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12079
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs/swift
>    Affects Versions: 2.6.0, 3.0.0-alpha1
>            Reporter: Gil Vernik
>            Assignee: Gil Vernik
>         Attachments: x-newest-optional0001.patch, 
> x-newest-optional0002.patch, x-newest-optional0003.patch, 
> x-newest-optional0004.patch, x-newest-optional0005.patch
>
>
> Current code always sends X-Newest header to Swift. While it's true that 
> Swift is eventual consistent and X-Newest will always get the newest version 
> from Swift, in practice this header will make Swift response very slow. 
> This header should be configured as an optional, so that it will be possible 
> to access Swift without this header and get much better performance. 
> This patch doesn't modify current behavior. All is working as is, but there 
> is an option to provide fs.swift.service.useXNewest = false. 
> Some background on Swift and X-Newest: 
> When a GET or HEAD request is made to an object, the default behavior is to 
> get the data from one of the replicas (could be any of them). The downside to 
> this is that if there are older versions of the object (due to eventual 
> consistency) it is possible to get an older version of the object. The upside 
> is that the for the majority of use cases, this isn't an issue. For the small 
> subset of use cases that need to make sure that they get the latest version 
> of the object, they can set the "X-Newest" header to "True". If this is set, 
> the proxy server will check all replicas of the object and only return the 
> newest object. The downside to this is that the request can take longer, 
> since it has to contact all the replicas. It is also more expensive for the 
> backend, so only recommended when it is absolutely needed.



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