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https://issues.apache.org/jira/browse/HADOOP-10634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14015522#comment-14015522
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Sumit Kumar commented on HADOOP-10634:
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That was a great suggestion [~ste...@apache.org] and thanks for clarifying
purpose of listLocatedStatus apis. It was confusing when i started working on
this patch. I've updated patch for MAPREDUCE-5907 to use these iterator based
apis that should address memory concerns.
I'm still going through HADOOP-10400, on high level it's a great enhancement
but i've few notes that i would share in a day or two (still going through the
patch).
> Add recursive list apis to FileSystem to give implementations an opportunity
> for optimization
> ---------------------------------------------------------------------------------------------
>
> Key: HADOOP-10634
> URL: https://issues.apache.org/jira/browse/HADOOP-10634
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs/s3
> Affects Versions: 2.4.0
> Reporter: Sumit Kumar
> Attachments: HADOOP-10634.patch
>
>
> Currently different code flows in hadoop use recursive listing to discover
> files/folders in a given path. For example in FileInputFormat (both mapreduce
> and mapred implementations) this is done while calculating splits. They
> however do this by doing listing level by level. That means to discover files
> in /foo/bar means they do listing at /foo/bar first to get the immediate
> children, then make the same call on all immediate children for /foo/bar to
> discover their immediate children and so on. This doesn't scale well for fs
> implementations like s3 because every listStatus call ends up being a
> webservice call to s3. In cases where large number of files are considered
> for input, this makes getSplits() call slow.
> This patch adds a new set of recursive list apis that give opportunity to the
> s3 fs implementation to optimize. The behavior remains the same for other
> implementations (that is a default implementation is provided for other fs so
> they don't have to implement anything new). However for s3 it provides a
> simple change (as shown in the patch) to improve listing performance.
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