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Posted to mapreduce-issues@hadoop.apache.org by "Tsuyoshi OZAWA (JIRA)" <ji...@apache.org> on 2012/12/10 06:17:21 UTC
[jira] [Created] (MAPREDUCE-4863) Adding aggregationWaitMap for
node-level combiner.
Tsuyoshi OZAWA created MAPREDUCE-4863:
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Summary: Adding aggregationWaitMap for node-level combiner.
Key: MAPREDUCE-4863
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4863
Project: Hadoop Map/Reduce
Issue Type: Sub-task
Components: applicationmaster
Affects Versions: 3.0.0
Reporter: Tsuyoshi OZAWA
Assignee: Tsuyoshi OZAWA
To manage node/rack-level combining, MRAppMaster needs to have a management information about outputs of completed MapTasks to be aggregated. AggregationWaitMap is used so that MRAppMaster decides whether or not MapTasks start to combine local MapOutputFiles.
AggregationWaitMap is a abstraction class of ConcurrentHashMap<String, ArrayList<TaskAttemptCompletionEvent>. These Events are candidate files to be aggregated.
When MapTasks are completed, MRAppMaster buffer TaskAttemptCompletionEvent into AggregationWaitMap to delay reducers' fethcing outputs from mappers until node-level aggregation are finished. After node-level aggreagtion, MRAppMaster write back mapAttemptCompletionEvents, to restart reducers' feching outputs from mappers.
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