[openstack-dev] [Nova] support for multiple active scheduler policies/drivers

Joe Gordon joe.gordon0 at gmail.com
Fri Jul 26 22:16:13 UTC 2013


On Wed, Jul 24, 2013 at 6:18 PM, Alex Glikson <GLIKSON at il.ibm.com> wrote:

> Russell Bryant <rbryant at redhat.com> wrote on 24/07/2013 07:14:27 PM:
>
> >
> > I really like your point about not needing to set things up via a config
> > file.  That's fairly limiting since you can't change it on the fly via
> > the API.
>
>
> True. As I pointed out in another response, the ultimate goal would be to
> have policies as 'first class citizens' in Nova, including a DB table, API,
> etc. Maybe even a separate policy service? But in the meantime, it seems
> that the approach with config file is a reasonable compromise in terms of
> usability, consistency and simplicity.
>

I do like your idea of making policies first class citizens in Nova, but I
am not sure doing this in nova is enough.  Wouldn't we need similar things
in Cinder and Neutron?    Unfortunately this does tie into how to do good
scheduling across multiple services, which is another rabbit hole all
together.

I don't like the idea of putting more logic in the config file, as it is
the config files are already too complex, making running any OpenStack
deployment  require some config file templating and some metadata magic
(like heat).   I would prefer to keep things like this in aggregates, or
something else with a REST API.  So why not build a tool on top of
aggregates to push the appropriate metadata into the aggregates.  This will
give you a central point to manage policies, that can easily be updated on
the fly (unlike config files).   In the long run I am interested in seeing
OpenStack itself have a strong solution for for policies as a first class
citizen, but I am not sure if your proposal is the best first step to do
that.




>
> Regards,
> Alex
>
> > --
> > Russell Bryant
>
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