[openstack-dev] Moving task flow to conductor - concern about scale

Peter Feiner peter at gridcentric.ca
Fri Jul 19 15:16:24 UTC 2013

On Fri, Jul 19, 2013 at 11:06 AM, Dan Smith <dms at danplanet.com> wrote:
> FWIW, I don't think anyone is suggesting a single conductor, and
> especially not a single database proxy.

This is a critical detail that I missed. Re-reading Phil's original email,
I see you're debating the ratio of nova-conductor DB proxies to
nova-conductor task flow managers.

I had assumed that some of the task management state would exist
in memory. Is it all going to exist in the database?

>> Since these queries are made frequently (i.e., easily 100 times
>> during instance creation) and while other global locks are held
>> (e.g., in the case of nova-compute's ResourceTracker), most of what
>> nova-compute does becomes serialized.
> I think your numbers are a bit off. When I measured it just before
> grizzly, an instance create was something like 20-30 database calls.
> Unless that's changed (a lot) lately ... :)

Ah perhaps... at least I had the order of magnitude right :-) Even
with 20-30 calls,
when a bunch of instances are being booted in parallel and all of the
database calls
are serialized, minutes are added in instance creation time.

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