[
https://issues.apache.org/jira/browse/HADOOP-2141?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Andy Konwinski updated HADOOP-2141:
-----------------------------------
Attachment: HADOOP-2141.patch
This patch implements a new algorithm for choosing tasks for speculative
execution.
Here is a high level overview of the algorithm:
If a task slot becomes available and there are less than SpeculativeCap
speculative tasks running:
* 1)Ignore the request if the TT's progressRate is < SlowNodeThreshold
* 2)Rank currently running, non-speculative tasks by estimated time left
* 3)Speculate task with highest-ranked and progressRate < SlowTaskThreshold
> 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: 0.15.0
> Reporter: Koji Noguchi
> Assignee: Andy Konwinski
> Attachments: 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.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
