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From "Arun C Murthy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-326) The lowest level map-reduce APIs should be byte oriented
Date Tue, 16 Feb 2010 17:59:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834340#action_12834340

Arun C Murthy commented on MAPREDUCE-326:

Jay - it would really help if you could explain your requirements better.

 Specifically, the option to launch an arbitrary runtime and give it it's inputsplit information
over STDIN would be really useful for us, could tell our Mapper and Reducer classes if they
need to initialize any business services prior to the main run, recycle those services across
runs, allow more flexibility with custom serializers, make it easier to involve a complicated
series of InputFormats.. (we need CombineFileInput and MultipleInput and a custom internal
SerDe, which in some cases necessitates redundant "gather jobs" prior to "processing jobs").

The _current_ proposal has *nothing* to do with passing input-split over STDIN or supporting
non-Java applications better and so on, we are only debating the apis for the Java MR framework.

> The lowest level map-reduce APIs should be byte oriented
> --------------------------------------------------------
>                 Key: MAPREDUCE-326
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-326
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>            Reporter: eric baldeschwieler
>         Attachments: MAPREDUCE-326-api.patch, MAPREDUCE-326.pdf
> As discussed here:
> https://issues.apache.org/jira/browse/HADOOP-1986#action_12551237
> The templates, serializers and other complexities that allow map-reduce to use arbitrary
types complicate the design and lead to lots of object creates and other overhead that a byte
oriented design would not suffer.  I believe the lowest level implementation of hadoop map-reduce
should have byte string oriented APIs (for keys and values).  This API would be more performant,
simpler and more easily cross language.
> The existing API could be maintained as a thin layer on top of the leaner API.

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