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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5907) Improve getSplits() performance for fs implementations that can utilize performance gains from recursive listing
Date Mon, 12 Feb 2018 12:52:00 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16360699#comment-16360699

Hadoop QA commented on MAPREDUCE-5907:

| (x) *{color:red}-1 overall{color}* |
|| 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  4s{color} | {color:red}
MAPREDUCE-5907 does not apply to trunk. Rebase required? Wrong Branch? See https://wiki.apache.org/hadoop/HowToContribute
for help. {color} |
|| Subsystem || Report/Notes ||
| 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/7333/console |
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This message was automatically generated.

> 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
>            Priority: Major
>         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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