[openstack-dev] RFC: Synchronizing hypervisor <-> nova state with event notifications

Daniel P. Berrange berrange at redhat.com
Tue Jan 22 11:02:38 UTC 2013

On Fri, Jan 18, 2013 at 01:04:59PM +0000, Day, Phil wrote:
> Wouldn't it be simpler in the first instance to just move the current
> polling into the nova-periodic service proposed by Michael
> (https://review.openstack.org/#/c/19539/ ) and shorten the polling
> interval ?

As previously discussed I don't think that nova-periodic as a service
is a good idea because it doesn't really solve any of the problems. It
just moves them elsewhere so you don't notice they exist as easily.
You still have the problem that any slow task in nova-periodic is going
to slow all the other tasks in that service.

> I know it's not as elegant but if this is a big problem maybe a quick
> fix while the callback / threading stuff gets sorted out. The original
> bug wasn't directly related to the amount of resources consumed by the
> Polling, just the impact it had due to the threading model.

I don't want to revisit this again later, so personally I'm only interested
in working on a long term scalable solution not yet another quick hack.
With the larger hosts that are around these days, you can have many 100's
of VMs per host and polling is going to be an scalability issue there.

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