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Date: Wed, 28 Dec 2011 12:01:32 +0000 (UTC)
From: "Sharad Agarwal (Commented) (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
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Subject: [jira] [Commented] (MAPREDUCE-3490) RMContainerAllocator counts
 failed maps towards Reduce ramp up
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-3490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13176621#comment-13176621 ] 

Sharad Agarwal commented on MAPREDUCE-3490:
-------------------------------------------

currently all bookkeeping and calculations in RMContainerAllocator are based on attempts not on tasks. there is one to one between attempt and container.

completedMapPercent is currently completed map *attempts* percentage. I looked in more detail. we can simply change this to reflect completed map tasks percentage. All information is readily available there in Job. So we need not maintain these counts in RMContainerAllocator. Arun also mentioned this. I am attaching a patch which drastically simplify this, without the need to add new events. Also I have removed the completedMaps and completedReduces counts in RMContainerAllocator.
Arun/Vinod - see if this make sense ?
                
> RMContainerAllocator counts failed maps towards Reduce ramp up
> --------------------------------------------------------------
>
>                 Key: MAPREDUCE-3490
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3490
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mr-am, mrv2
>    Affects Versions: 0.23.0
>            Reporter: Siddharth Seth
>            Assignee: Arun C Murthy
>            Priority: Blocker
>         Attachments: MAPREDUCE-3490.patch, MAPREDUCE-3490.patch, MAPREDUCE-3490.patch, MAPREDUCE-3490.patch, MR-3490-alternate.patch
>
>
> The RMContainerAllocator does not differentiate between failed and successful maps while calculating whether reduce tasks are ready to launch. Failed tasks are also counted towards total completed tasks. 
> Example. 4 failed maps, 10 total maps. Map%complete = 4/14 * 100 instead of being 0.

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