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https://issues.apache.org/jira/browse/HADOOP-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12709802#action_12709802
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Devaraj Das commented on HADOOP-2141:
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bq. In the future, we may consider the overall performance of TTs w.r.t all
tasks it has run so far and make some decisions based on that for this special
case.
I meant tasks across all jobs.
> 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: 0.21.0
> Reporter: Koji Noguchi
> Assignee: Andy Konwinski
> Attachments: 2141.patch, HADOOP-2141-v2.patch, HADOOP-2141-v3.patch,
> HADOOP-2141-v4.patch, HADOOP-2141-v5.patch, HADOOP-2141-v6.patch,
> HADOOP-2141.patch, HADOOP-2141.v7.patch, HADOOP-2141.v8.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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