[openstack-dev] [Nova][Schduler] Volunteers wanted for a modest proposal for an external scheduler in our lifetime

Robert Collins robertc at robertcollins.net
Thu Nov 28 18:12:03 UTC 2013

On 29 November 2013 04:50, Gary Kotton <gkotton at vmware.com> wrote:

> I am not really sure how we can have a client tree without even having
> discussed the API's and interfaces. From the initial round of emails the
> intention was to make use of the RPC mechanism to speak with the scheduler.

It still is. We have an existing RPC API in the nova/scheduler tree.

> One option worth thinking about is to introduce a new scheduling driver to
> nova - this driver will interface with the external scheduler. This will
> let us define the scheduling API, model etc, without being in the current
> confines of Nova. This will also enable all of the other modules, for
> example Cinder to hook into it.

The problem is that that is the boil-the-ocean approach that hasn't
succeeded for several cycles. We have interest in trying something new
- there are three failure modes I can see:
A - we fail to split it out enough, and noone else uses it.
B - we introduce a performance / correctness problem during the split out
C - we stall and don't do anything

Right now, I am mainly worried about B. Getting good APIs is step two
after getting a solid split out scheduler.


Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud

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