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From Bill Farner <wfar...@apache.org>
Subject Re: Bug in Preemptor?
Date Sun, 14 Sep 2014 15:49:47 GMT
Thanks for raising the concern!

> Unfortunately, it seems the preemptor cannot handle constraints

Sounds like you are saying the Preemptor is only matching resources and not
constraints?

I'm on a phone, so I may have missed something, but my read is that the
preemptor lets SchedulingFilter.filter deal with satisfying constraints.
 If the SchedulingFilter finds a constraint violation with the scheduling
proposal, it flags that with a Veto.

On Sunday, September 14, 2014, Stephan Erb <stephan@dev.static-void.de>
wrote:

> Hi together,
>
> I was scrolling through Preemptor.java and noticed that tasks might be
> preempted unnecessarily.
>
> If I am not mistaken, the code works as follows:
>
>
>     for slave in slaves:
>       while SchedulingFilter.filter is still yielding vetos:
>         add preemptable task of slave to list toPreemptTasks
>
>       if toPreemptTasks has some tasks:
>         preempt
>         return
>
>
> SchedulingFilter is checking for available resources and constraints.
> Unfortunately, it seems the preemptor cannot handle constraints: It may
> drain an entire slave trying to make room for a new task. However, if
> this task has a constraint which prevents it from being scheduled on
> this slave at all, then the other tasks are preempted unnecessarily.
>
> Is my analysis correct here?
>
> Best Regards,
> Stephan
>
>
>
>
>
>

-- 
-=Bill

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