[jira] Updated: (HADOOP-3840) Support pluggable speculative execution

["Owen O'Malley (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-3840?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Owen O'Malley updated HADOOP-3840:
----------------------------------

    Resolution: Won't Fix
        Status: Resolved  (was: Patch Available)

I propose that we mark this as won't fix. I think that the interfaces to the speculative execution are integrated enough that this would be difficult to get right. Please do submit your and Andy's patch for improved speculative execution.

> Support pluggable speculative execution
> ---------------------------------------
>
>                 Key: HADOOP-3840
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3840
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Matei Zaharia
>            Assignee: Matei Zaharia
>            Priority: Minor
>         Attachments: HADOOP-3840-v1.txt, HADOOP-3840-v2.patch, HADOOP-3840-v3.patch
>
>
> HADOOP-3412 introduced an way to plug in a job scheduler for MapReduce. However, the job schedulers all use JobInProgress.obtainNewMapTask or obtainNewReduceTask to select tasks to run from each job, which uses a threshold-based speculative execution algorithm that has several shortcomings (see JIRAs about the scheduler not speculating tasks that freeze after having 80% progress for example). As a first step towards supporting better speculative execution policies while not breaking backwards compatibility, it makes sense to make the speculative execution policy pluggable. Luckily this is easy - we just need an interface around obtainNewMapTask and obtainNewReduceTask. This JIRA suggests adding a TaskSelector abstract class which, given a TaskTracker and a JobInProgress, chooses a task to run on the tracker. A default implementation that uses the current methods in JobInProgress is provided. Both TaskSchedulers in trunk are changed to use TaskSelector.
> In addition, there are methods to count how many speculative tasks a job needs, since TaskInProgress.hasSpeculative() may not work if we change the algorithm for selecting speculative tasks. This count is needed for some schedulers, such as a fair scheduler.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.