[openstack-dev] [scheduler] Making nova-scheduler extension friendly

Russell Bryant rbryant at redhat.com
Wed Jan 16 23:33:13 UTC 2013

On 01/16/2013 06:23 PM, Chris Behrens wrote:
> There's movement to move common scheduler code into oslo… at which point it definitely needs to be generic enough to handle the basic functionality of scheduling for both nova and cinder.
> There's also discussion about turning the scheduler into its own openstack service… (there may be a blueprint for this already).   As an example, when using volumes with compute, you may want to schedule an instance based on both compute and volume information.  This type of scheduler doesn't belong in nova because volumes live outside.   A new scheduling service that knows about 'all of the things' is needed.  When we have that, how scheduling works in nova changes quite a bit.  Nova would ask the scheduler questions and get responses vs proxying messages via it.
> What other topics beside 'compute' are you thinking of below?

Indeed, and is it something that you intend to submit at some point?  I
would honestly resist efforts to make the code in nova more generic (and
more complicated) unless there is also a patch with it to make use of it.

I would look at helping make as much of the scheduler code generic
enough to move into oslo-incubator so that it can be shared between nova
and cinder.  If it's generic enough to be shared between those two, it
may be generic enough to use in your own custom service.

I'd like to see continued movement to share scheduler code between nova
and cinder sooner rather than later.  Otherwise, the more they diverge,
the harder that will be to accomplish.

Russell Bryant

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