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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-981) Attribute to mark Mappers and Reducers as side-effect free
Date Mon, 05 Feb 2007 23:00:05 GMT
Attribute to mark Mappers and Reducers as side-effect free
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                 Key: HADOOP-981
                 URL: https://issues.apache.org/jira/browse/HADOOP-981
             Project: Hadoop
          Issue Type: Improvement
          Components: mapred
    Affects Versions: 0.11.0
            Reporter: Owen O'Malley
             Fix For: 0.12.0


There should be an annotation to mark Mapper and Reducer classes as side-effect free. This
annotation could then be used to disable speculative execution for such classes. Furthermore,
defining a class without the NoSideEffect attribute as a combiner would be a run-time error.


@NoSideEffects
class MyMapper extends MapReduceBase implements Mapper { ... }

would declare that MyMapper may be run speculatively.

@NoSideEffects
class MyReducer extends MapReduceBase implements Reducer { ...}

declares that MyReducer can be run speculative and as a combiner.

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