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https://issues.apache.org/jira/browse/MAPREDUCE-2454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13499171#comment-13499171
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Mariappan Asokan commented on MAPREDUCE-2454:
---------------------------------------------
Hi Arun,
Thanks for your comments. Regarding your comment on passing shuffle to
merge: I did this with the following rationale:
* Conceptually, merge can take its input from different types of sources; today
we have two types: one is Shuffle and the other is from local files for a local
job. Tomorrow, we may add a hybrid of Shuffle and local map output files(this
will involve adding another method in the ReduceInputMerger) to avoid shuffling
local map outputs for optimizing the performance. This new approach which
decouples Shuffle and Merge is more flexible.
* In current implementation, Shuffle which is supposed to transfer bytes from
map outputs to the merger, is also returning a RawKeyValueIterator which in
turn implies it is doing more than transferring bytes.
-- Asokan
> Allow external sorter plugin for MR
> -----------------------------------
>
> Key: MAPREDUCE-2454
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2454
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Affects Versions: 2.0.0-alpha, 3.0.0, 2.0.2-alpha
> Reporter: Mariappan Asokan
> Assignee: Mariappan Asokan
> Priority: Minor
> Labels: features, performance, plugin, sort
> Attachments: HadoopSortPlugin.pdf, HadoopSortPlugin.pdf,
> KeyValueIterator.java, MapOutputSorterAbstract.java, MapOutputSorter.java,
> mapreduce-2454-modified-code.patch, mapreduce-2454-modified-test.patch,
> mapreduce-2454-new-test.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454.patch, mapreduce-2454.patch,
> mapreduce-2454.patch, mapreduce-2454-protection-change.patch,
> mr-2454-on-mr-279-build82.patch.gz, MR-2454-trunkPatchPreview.gz,
> ReduceInputSorter.java
>
>
> Define interfaces and some abstract classes in the Hadoop framework to
> facilitate external sorter plugins both on the Map and Reduce sides.
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