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Date: Thu, 16 Oct 2008 16:00:44 -0700 (PDT)
From: "Arun C Murthy (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Updated: (HADOOP-2141) speculative execution start up
 condition based on completion time
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     [ https://issues.apache.org/jira/browse/HADOOP-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Arun C Murthy updated HADOOP-2141:
----------------------------------

    Affects Version/s:     (was: 0.20.0)
                       0.19.0
        Fix Version/s:     (was: 0.19.0)
                       0.20.0

> speculative execution start up condition based on completion time
> -----------------------------------------------------------------
>
>                 Key: HADOOP-2141
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2141
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Koji Noguchi
>            Assignee: Andy Konwinski
>             Fix For: 0.20.0
>
>         Attachments: HADOOP-2141-v2.patch, HADOOP-2141-v3.patch, HADOOP-2141.patch
>
>
> We had one job with speculative execution hang.
> 4 reduce tasks were stuck with 95% completion because of a bad disk. 
> Devaraj pointed out 
> bq . One of the conditions that must be met for launching a speculative instance of a task is that it must be at least 20% behind the average progress, and this is not true here.
> It would be nice if speculative execution also starts up when tasks stop making progress.
> Devaraj suggested 
> bq. Maybe, we should introduce a condition for average completion time for tasks in the speculative execution check. 

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