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Posted to mapreduce-issues@hadoop.apache.org by "Steve Loughran (JIRA)" <ji...@apache.org> on 2018/02/12 12:49:00 UTC
[jira] [Updated] (MAPREDUCE-5907) Improve getSplits() performance
for fs implementations that can utilize performance gains from recursive
listing
[ https://issues.apache.org/jira/browse/MAPREDUCE-5907?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Steve Loughran updated MAPREDUCE-5907:
--------------------------------------
Labels: (was: BB2015-05-TBR)
> 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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