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https://issues.apache.org/jira/browse/HADOOP-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Devaraj Das updated HADOOP-2141:
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Resolution: Fixed
Release Note: Improves the speculative execution heuristic. The heuristic
is currently based on the progress-rates of tasks and the expected time of
completion. Also, statistics about trackers are collected, and speculative
tasks are not given to the ones deduced to be slow. (was: Updated speculative
execution scheduler)
Hadoop Flags: [Reviewed]
Status: Resolved (was: Patch Available)
I just committed this. Thanks Andy!
> 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
> Fix For: 0.21.0
>
> Attachments: 2141.4.patch, 2141.5.patch, 2141.6.patch, 2141.7.patch,
> 2141.8.2.patch, 2141.8.3.patch, 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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