Open Stack

Hi all,

One of my long time goal since I started contributing to OpenStack is
to try to remove polling where I can. With Zaqar WebSocket support, we
now have a transport available for users to connect to, and where we
can push notifications. We already leveraged that in Heat [1], so that
you can manipulate a stack and you'll be notified when its status
changes.

Still, not everyone uses Heat, and under the hood it still polls for
you. We should be able to use the various notifications that projects
publish to push similar events. Ceilometer already consumes those
notifications and try to make them somewhat consumable [2].

The missing piece is something that bridges Ceilometer and Zaqar. I
wrote a small service [3] which provide a simple API, so that you can
say "Subscribe to those events and send them to this queue". The data
flow looks like this:

Service (Nova, Neutron) -> Notification -> Ceilometer -> Bridge ->
Zaqar -> User.

This way, you'll get a Zaqar message per event, with some filtering
done by the bridge service. It's far from being ideal, as the
notification format is a endless topic of conversation, but I hope
that if we start using it things will move further. I also hope I can
get some feedback on the approach.

One question is whether we want to skip the subscription phase, and
simply makes all those events available to users at a known place (for
example, all events in the Zaqar queue events-queue, or maybe all Nova
events in the compute-events-queue). That pushes filtering to the
user, but it also simplifies the bootstrap phase.

Anyway, I wanted to send this before the summit so that people
interested can come talk to me.

Thanks,

-- 
Thomas

[1] http://docs.openstack.org/developer/heat/template_guide/environment.html#retrieving-events

[2] http://docs.openstack.org/developer/ceilometer/events.html#events-from-notifications

[3] https://github.com/therve/nabu