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Posted to mapreduce-issues@hadoop.apache.org by "Robert Joseph Evans (Created) (JIRA)" <ji...@apache.org> on 2011/12/08 17:13:40 UTC
[jira] [Created] (MAPREDUCE-3520) Allow for metrics to be exchanged
between mapps and reduces
Allow for metrics to be exchanged between mapps and reduces
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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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