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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-326) The lowest level map-reduce APIs should be byte oriented
Date Tue, 16 Feb 2010 19:47:28 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12834412#action_12834412

Chris Douglas commented on MAPREDUCE-326:

bq. Jay> As long as everything is directly tied to Hadoop Writables in Java, there's only
going to be so far we can go beyond the basic wordcount program. If we have a common, robust,
low-level binary API that's exposed for all to use, we could rapidly see framework implementations
in a few langauges, more flexible input methods, different serialization formats, non-mapreduce
distributed computing ("just distribute these runnables across the cluster and tell me when
they're done"), etc.

The serialization has been pluggable since HADOOP-1986, so non-Writables have worked for some
time. The types are restricted to an exact match in MapReduce, but there is consensus on weakening
that requirement. I'm not sure how you're reading this proposal, but I don't think it's offering
what you think and/or the framework is more versatile than you expect.

> 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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