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On 07/22/2013 05:15 PM, Alex Glikson wrote:
> Dear all,
> 
> Following the initial discussions at the last design summit, we have
> published the design [2] and the first take on the implementation [3] of
> the blueprint adding support for multiple active scheduler
> policies/drivers [1].
> In a nutshell, the idea is to allow overriding the 'default' scheduler
> configuration parameters (driver, filters, their configuration
> parameters, etc) for particular host aggregates. The 'policies' are
> introduced as sections in nova.conf, and each host aggregate can have a
> key-value specifying the policy (by name).
> 
> Comments on design or implementation are welcome!
> 
> Thanks,
> Alex
> 
> 
> [1] https://blueprints.launchpad.net/nova/+spec/multiple-scheduler-drivers
> [2] https://wiki.openstack.org/wiki/Nova/MultipleSchedulerPolicies
> [3] https://review.openstack.org/#/c/37407/

Thanks for bringing this up.  I do have some comments.

The current design shows 2 different use cases for how a scheduling
policy would be chosen.

#1 - policy associated with a host aggregate

This seems very odd to me.  Scheduling policy is what chooses hosts, so
having a subset of hosts specify which policy to use seems backwards.

#2 - via a scheduler hint

It also seems odd to have the user specifying scheduling policy.  This
seems like something that should be completely hidden from the user.

How about just making the scheduling policy choice as simple as an item
in the flavor extra specs?

The design also shows some example configuration.  It shows a global set
of enabled scheduler filters, and then policy specific tweaks of filter
config (CPU allocation ratio in the example).  I would expect to be able
to set a scheduling policy specific list of scheduler filters and
weights, as well.

-- 
Russell Bryant