[openstack-dev] [Nova][Scheduler] Policy Based Scheduler and Solver Scheduler

Khanh-Toan Tran khanh-toan.tran at cloudwatt.com
Thu Jan 30 11:36:16 UTC 2014

Hi Sylvain,

1) Some Filters such as AggregateCoreFilter, AggregateRAMFilter can change
its parameters for aggregates. But what if admin wants to change for all
hosts in an availability-zone? Does he have to rewrite all the parameters
in all aggregates? Or should we create a new AvailabilityZoneCoreFilter?

The Policy Based Scheduler (PBS)  blueprint separates the effect (filter
according to Core) from its target (all hosts in an aggregate, or in an
availability-zone). It will benefit all filters, not just CoreFilter or
RAMFilter, so that we can avoid creating for each filter XFilter the
AggregateXFilter and AvailabilityZoneWFilter from now on. Beside, if admin
wants to apply the a filter to some aggregates (or availability-zone) and
not the other (don’t call filters at all, not just modify parameters), he
can do it. It help us avoid running all filters on all hosts.

2) In fact, we also prepare for a separated scheduler in which PBS is a
very first step of it, that’s why we purposely separate the Policy Based
Scheduler from Policy Based Scheduling Module (PBSM) [1] which is the core
of our architecture. If you look at our code, you will see that
Policy_Based_Scheduler.py is only slightly different from Filter
Scheduler. That is because we just want a link from Nova-scheduler to
PBSM. We’re trying to push some more management into scheduler without
causing too much modification, as you can see in the patch .

Thus I’m very happy when Gantt is proposed. As I see it, Gantt is based on
Nova-scheduler code, with the planning on replacing nova-scheduler in J.
The separation from Nova will be complicated, but not on scheduling part.
Thus integrating PBS and PBSM into Gantt would not be a problem.

Best regards,



De : Sylvain Bauza [mailto:sylvain.bauza at gmail.com]
Envoyé : jeudi 30 janvier 2014 11:16
À : OpenStack Development Mailing List (not for usage questions)
Objet : Re: [openstack-dev] [Nova][Scheduler] Policy Based Scheduler and
Solver Scheduler

Hi Khanh-Toan,

I only have one comment on your proposal : why are you proposing something
new for overcommitments with aggregates while the AggregateCoreFilter [1]
and AggregateRAMFilter [2]already exist, which AIUI provide same feature ?

I'm also concerned about the scope of changes for scheduler, as Gantt is
currently trying to replace it. Can we imagine such big changes to be
committed on the Nova side, while it's planned to have a Scheduler service
in the next future ?




2014-01-30 Khanh-Toan Tran <khanh-toan.tran at cloudwatt.com>

There is an unexpected line break in the middle of the link, so I post it


> -----Message d'origine-----
> De : Khanh-Toan Tran [mailto:khanh-toan.tran at cloudwatt.com]
> Envoyé : mercredi 29 janvier 2014 13:25
> À : 'OpenStack Development Mailing List (not for usage questions)'
> Objet : [openstack-dev] [Nova][Scheduler] Policy Based Scheduler and

> Scheduler
> Dear all,
> As promised in the Scheduler/Gantt meeting, here is our analysis on the
> connection between Policy Based Scheduler and Solver Scheduler:
> https://docs.google.com/document/d/1RfP7jRsw1mXMjd7in72ARjK0fTrsQv1bq
> olOri
> This document briefs the mechanism of the two schedulers and the
possibility of
> cooperation. It is my personal point of view only.
> In a nutshell, Policy Based Scheduler allows admin to define policies
for different
> physical resources (an aggregate, an availability-zone, or all
> infrastructure) or different (classes of) users. Admin can modify
> (add/remove/modify) any policy in runtime, and the modification effect
is only
> in the target (e.g. the aggregate, the users) that the policy is defined
to. Solver
> Scheduler solves the placement of groups of instances simultaneously by
> all the known information into a integer linear system and uses Integer
> solver to solve the latter. Thus relation between VMs and between VMs-
> computes are all accounted for.
> If working together, Policy Based Scheduler can supply the filters and
> following the policies rules defined for different computes.
> These filters and weighers can be converted into constraints & cost
function for
> Solver Scheduler to solve. More detailed will be found in the doc.
> I look forward for comments and hope that we can work it out.
> Best regards,
> Khanh-Toan TRAN
> _______________________________________________
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev

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