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https://issues.apache.org/jira/browse/MAPREDUCE-5352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13695934#comment-13695934
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Siddharth Seth commented on MAPREDUCE-5352:
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Thanks for looking at the patch and trying it out Devaraj.
It looks like if maxSize is not set - CombineFileInputFormat will end up
generating 1 split per node. Since that's been the behaviour all along - I'll
upload another patch with a different comment.
> Optimize node local splits generated by CombineFileInputFormat
> ---------------------------------------------------------------
>
> Key: MAPREDUCE-5352
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5352
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Affects Versions: 2.0.5-alpha
> Reporter: Siddharth Seth
> Assignee: Siddharth Seth
> Attachments: MAPREDUCE-5352.1.txt
>
>
> CombineFileInputFormat currently walks through all available nodes and
> generates multiple (maxSplitsPerNode) splits on a single node before
> attempting to generate splits on subsequent nodes. This ends up reducing the
> possibility of generating splits for subsequent nodes - since these blocks
> will no longer be available for subsequent nodes. Allowing splits to go 1
> block above the max-split-size makes this worse.
> Allocating a single split per node in one iteration, should help increase the
> distribution of splits across nodes - so the subsequent nodes will have more
> blocks to choose from.
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