[jira] [Commented] (MAPREDUCE-5907) Improve getSplits() performance for fs implementations that can utilize performance gains from recursive listing

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16260506#comment-16260506 ] 

Hadoop QA commented on MAPREDUCE-5907:
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| (x) *{color:red}-1 overall{color}* |
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| {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  5s{color} | {color:red} MAPREDUCE-5907 does not apply to trunk. Rebase required? Wrong Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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| JIRA Issue | MAPREDUCE-5907 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12648040/MAPREDUCE-5907-3.patch |
| Console output | https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/7230/console |
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> Improve getSplits() performance for fs implementations that can utilize performance gains from recursive listing
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5907
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5907
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 2.4.0
>            Reporter: Sumit Kumar
>            Assignee: Sumit Kumar
>              Labels: BB2015-05-TBR
>         Attachments: MAPREDUCE-5907-2.patch, MAPREDUCE-5907-3.patch, MAPREDUCE-5907.patch
>
>
> FileInputFormat (both mapreduce and mapred implementations) use recursive listing 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 object store based fs implementations like s3 and swift because every listStatus call ends up being a webservice call to backend. 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 gives opportunity to the fs implementations 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 objectstore based fs implementations it provides a simple change to include recursive flag as true (as shown in the patch) to improve listing performance.



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