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https://issues.apache.org/jira/browse/MAPREDUCE-3520?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Joseph Evans updated MAPREDUCE-3520:
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Summary: Allow for metrics to be exchanged between maps and reduces (was:
Allow for metrics to be exchanged between mapps and reduces)
> Allow for metrics to be exchanged between maps and reduces
> ----------------------------------------------------------
>
> Key: MAPREDUCE-3520
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3520
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Components: mrv2
> Affects Versions: 0.24.0
> Reporter: Robert Joseph Evans
>
> Some people on the mailing lists have requested having read access in
> reducers to counters that were set by mappers. I propose that we provide a
> new interface for doing this. The counter data in addition to being set
> periodically to the Application Master would be put into the intermediate
> output of the mapper for each reducer and be specially marked as such. When
> the reducers fetch that data they can combine it together and provide a read
> only interface to it.
> This allows users to potentially optimize their code on the reducer side if
> they know some special metadata before hand.
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