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https://issues.apache.org/jira/browse/HADOOP-12079?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14634653#comment-14634653
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Gil Vernik commented on HADOOP-12079:
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I will make changes. But i think this header is not so important for Swift, of
course depends on the use case. If some application write data with same name
all over again and than read it all the time without any delay- than Swift is
not a good choice, and people can use local file system.
Swift is good for it's use cases, like achieve or dozens of other cases. For
those cases X-Newest make performance slow without any benefit.
> 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
> Reporter: Gil Vernik
> Assignee: Gil Vernik
> Fix For: 2.6.1, 3.0.0
>
> 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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