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Date: Thu, 19 Nov 2009 01:03:39 +0000 (UTC)
From: "Scott Chen (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1198) Alternatively schedule different
 types of tasks in fair share scheduler
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12779778#action_12779778 ] 

Scott Chen commented on MAPREDUCE-1198:
---------------------------------------

My intention is that when a task type is rejected once, it should always be rejected. Since it is the first condition in || (or), if it is true the following condition checks will be skipped. 

But you are right, this will not change the logic if we remove it. If it is confusing, I think it is OK to remove it.

> Alternatively schedule different types of tasks in fair share scheduler
> -----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1198
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1198
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: contrib/fair-share
>    Affects Versions: 0.22.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>             Fix For: 0.22.0
>
>         Attachments: MAPREDUCE-1198-v1.patch, MAPREDUCE-1198-v2.patch
>
>
> Matei has mentioned in MAPREDUCE-961 that the current scheduler will first try to launch map tasks until canLaunthTask() returns false then look for reduce tasks. This might starve reduce task. He also mention that alternatively schedule different types of tasks can solve this problem.

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