[openstack-dev] [all] how to send messages (and events) to our users

Sandy Walsh sandy.walsh at RACKSPACE.COM
Wed Apr 8 16:38:10 UTC 2015

>From: Clint Byrum <clint at fewbar.com>
>Sent: Wednesday, April 8, 2015 1:15 PM
>There's this:

Hmm, that looks interesting. Will read.

>I also want to point out that what I'd actually rather see is that all
>of the services provide functionality like this. Users would be served
>by having an event stream from Nova telling them when their instances
>are active, deleted, stopped, started, error, etc.
>Also, I really liked Sandy's suggestion to use the notifications on the
>backend, and then funnel them into something that the user can consume.
>The project they have, yagi, for putting them into atom feeds is pretty
>interesting. If we could give people a simple API that says "subscribe
>to Nova/Cinder/Heat/etc. notifications for instance X, and put them
>in an atom feed", that seems like something that would make sense as
>an under-the-cloud service that would be relatively low cost and would
>ultimately reduce load on API servers.


Yes. It would be so good to pull apart the state-machine that is Nova and
just emit completed actions via notifications. Then, have something like
TaskFlow externalize the orchestration. Do away with RPC-over-AMQP. 

And, anyone that is interested in the transitions can eavesdrop on the

In our transition from StackTach.v2 to StackTach.v3 in production we simply
cloned the notification feeds so the two systems can run in parallel*. No
changes to OpenStack, no disruption of service. Later, we'll just kill off 
the v2 queues.


* we did this in Yagi, since olso-messaging doesn't support multiple queues
from one routing key. 

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