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https://issues.apache.org/jira/browse/MAPREDUCE-4863?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tsuyoshi OZAWA updated MAPREDUCE-4863:
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Attachment: 0002-Adding-aggregationWaitMap-for-node-level-combiner.patch
First patch.
> 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
> Attachments:
> 0002-Adding-aggregationWaitMap-for-node-level-combiner.patch
>
>
> 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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