hadoop-common-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Matei Zaharia (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3412) Refactor the scheduler out of the JobTracker
Date Wed, 16 Jul 2008 00:29:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613803#action_12613803
] 

Matei Zaharia commented on HADOOP-3412:
---------------------------------------

bq. The users of the getQueueNames() and getJobs(queue) would be the web ui and the command
line tools "bin/hadoop job". Of course the ordering doesn't have to be exclusive, but almost
all schedulers will have a rough priority within the queue. It is basically about providing
information about the scheduler to the user. Does that make sense?

I see, I guess it's an issue of increasing API complexity vs benefit of seeing jobs in sorted
order then. Personally I'd prefer if the API that the scheduler had to implement was a simple
as possible. I think there are two solutions to the problem you're mentioning with providing
info about the scheduler to the user:
* Short-term, just sort the jobs by submit time and also tell the user the priority of each
job. This is easy to parse (the user can even figure out which job is which based on the order
they submitted them), and it's also what the web UI currently provides.
* Longer-term, it would be nice if schedulers (and maybe other elements of Hadoop as well)
could simply register other web apps / servlets on the StatusHttpServer. This is actually
how I'm planning to create a dashboard for my scheduler. Hopefully the only thing it requires
is adding a getter for the server.

> 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.

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


Mime
View raw message