Open Stack

On Jun 26, 2014, at 5:25 PM, Zane Bitter <zbitter at redhat.com>
 wrote:

> On 23/06/14 19:25, Clint Byrum wrote:
>> Hello! I would like to turn your attention to this specification draft
>> that I've written:
>> 
>> https://review.openstack.org/#/c/100012/1/specs/convergence-continuous-observer.rst
>> 
>> Angus has suggested that perhaps Ceilometer is a better place to handle
>> this. Can you please comment on the review, or can we have a brief
>> mailing list discussion about how best to filter notifications?
>> 
>> Basically in Heat when a user boots an instance, we would like to act as
>> soon as it is active, and not have to poll the nova API to know when
>> that is. Angus has suggested that perhaps we can just tell ceilometer to
>> hit Heat with a web hook when that happens.
> 
> I'm all in favour of having Ceilometer filter the firehose for us if we can :)
> 
> Webhooks would seem to add a lot of overhead though (set up + tear down a connection for every notification), that could perhaps be avoided by using a message bus? Given that both setting up and receiving these notifications would be admin-only operations, is there any benefit to handling them through a webhook API rather than through oslo.messaging?
> 
> cheers,
> Zane.

In larger OpenStack deployments, the different services probably don't share the same message bus. While I certainly agree oslo.messaging and/or oslo.notifications should be an option (and probably the default one at that), I think there should still be an option to use ceilometer or some other notification mechanism. As long as its pluggable, I don't think anyone would be too fussed.