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From "Tsuyoshi OZAWA (JIRA)" <j...@apache.org>
Subject [jira] [Work started] (MAPREDUCE-4863) Adding aggregationWaitMap for node-level combiner.
Date Fri, 18 Jan 2013 05:58:13 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4863?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Work on MAPREDUCE-4863 started by Tsuyoshi OZAWA.

> 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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