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https://issues.apache.org/jira/browse/YARN-10444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17343836#comment-17343836
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Wei-Chiu Chuang commented on YARN-10444:
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Rebased PR https://github.com/apache/hadoop/pull/2584
> use openFile() with sequential IO for localizing files.
> -------------------------------------------------------
>
> Key: YARN-10444
> URL: https://issues.apache.org/jira/browse/YARN-10444
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: nodemanager
> Affects Versions: 3.3.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Minor
>
> HADOOP-16202 adds standard options for declaring the read/seek
> Policy when reading a file. These should be set to sequential IO
> When localising resources, so that if the default/cluster settings
> For a file system are optimized for random IO, artifact downloads
> are still read at the maximum speed possible (one big GET to the EOF).
> Most of this happens in hadoop-common, but some tuning of FSDownload
> can assist
> * tar/jar download must also be sequential
> * if the FileStatus is passed around, that can be used
> in the open request to skip checks when loading the file.
>
> Together this can save 3 HEAD requests per resource, with the sequential
> IO avoiding any splitting of the big read into separate block GETs
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