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https://issues.apache.org/jira/browse/HADOOP-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tom White updated HADOOP-3412:
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Attachment: JobScheduler-v10.patch
A new patch (v10) with the following changes:
* The scheduling classes are package private as that seems to be the consensus
for the moment.
* TaskScheduler returns a list of Tasks as suggested by Arun to facilitate
HADOOP-3136.
* This Jira should not change the default scheduling algorithm, so I've made
JobQueueTaskScheduler use the same algorithm as JobTracker currently does (in
the getNewTaskForTaskTracker method). This keeps the padding code - thanks for
pointing this out Hemanth. I've split out Brice's algorithm that limits the
maximum number of tasks per job to a class called LimitTasksPerJobTaskScheduler.
* The assignTasks method now takes a TaskTrackerStatus object, which serves as
a representation of a tasktracker.
> Refactor the scheduler out of the JobTracker
> --------------------------------------------
>
> Key: HADOOP-3412
> URL: https://issues.apache.org/jira/browse/HADOOP-3412
> Project: Hadoop Core
> Issue Type: Improvement
> Components: mapred
> Reporter: Brice Arnould
> Assignee: Brice Arnould
> Priority: Minor
> Fix For: 0.19.0
>
> Attachments: JobScheduler-v10.patch, JobScheduler-v9.1.patch,
> JobScheduler-v9.2.patch, JobScheduler-v9.patch, JobScheduler.patch,
> JobScheduler_v2.patch, JobScheduler_v3.patch, JobScheduler_v3b.patch,
> JobScheduler_v4.patch, JobScheduler_v5.patch, JobScheduler_v6.1.patch,
> JobScheduler_v6.2.patch, JobScheduler_v6.3.patch, JobScheduler_v6.4.patch,
> JobScheduler_v6.patch, JobScheduler_v7.1.patch, JobScheduler_v7.patch,
> JobScheduler_v8.patch, RackAwareJobScheduler.java,
> SimpleResourceAwareJobScheduler.java
>
>
> First I would like warn you that my proposition is assumed to be very naive.
> I just hope that reading it won't make you lose time.
> h4. The aim
> It seems to me that improving Hadoop scheduling could be very profitable.
> But, it is hard to implement and compare schedulers, because the scheduling
> logic is mixed within the rest of the JobTracker.
> This bug is the first step of an attempt to improve the Hadoop scheduler. It
> re-implements the current scheduling algorithm in a separate class called
> JobScheduler. This new class is instantiated in the JobTracker.
> h4. Bug fixed as a side effects
> This patch probably cannot be submited as it is.
> A first difficulty is that it does not have exactly the same behaviour than
> the current JobTracker. More precisely, it doesn't re-implement things like
> code that seems to be never called or concurency problems.
> I wrote TOCONFIRM where my proposition differ from the current
> implementation, so you can find them easily.
> I know that fixing bugs silently is bad. So, independently of what you decide
> about this patch, I will open issues for bugs that you confirm.
> h4. Other side effects
> Another side effect of this patch is to add documentation about each step of
> the scheduling. I hope that it will help future improvement by lowering the
> level required to contribute to the scheduler.
> It also reduces the complexity and the granularity of the JobTracker (making
> it more parallel).
> h4. The future
> If you feel that this is a step the right direction, I will try to propose a
> JobSchedulerInterface that many JobSchedulers could implement and to propose
> alternatives to the current « FifoJobScheduler ». If some of you have ideas
> about that please tell ^^ I will also open issues for things marked as FIXME
> in the patch.
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