[openstack-dev] [OSLO][RPC] AMQP / ZeroMQ control_exchange vs port numbers

Julien Danjou julien at danjou.info
Fri Apr 26 14:38:55 UTC 2013

On Fri, Apr 26 2013, Russell Bryant wrote:

> I'm trying to understand the proposal ... would this mean taking some
> ceilometer code and making a notification driver with it that
> re-formats notifications into the form you want them in?

That's exactly what Ceilometer does since the beginning. It collects
notifications, and build metrics out of this.

> I'm still not feeling great about this.  The fact that ceilometer
> doubles the messaging load doesn't seem like a good justification for
> crossing the line into cross-project rpc.

I think we all already do cross-project RPC, it's just that all projects
relies on HTTP rather than on oslo's RPC.
For Ceilometer, we do envision HTTP to publish metrics too, but since we
don't have it so far, and since that from a deployer point of view RPC
is internal and makes sense, it doesn't shock me to use it for such a

> If consuming notifications, and then spitting data back out on the bus
> is a scale issue then ... just don't do that?

That would be the point of the notification driver, dividing by 2 what a
service would have to emit.

I don't there's point forcing people to send the notification to RPC.
The notification system has driver for a good reason, so people can do
whatever they want with them (send them, log them). Ceilometer goals is
to build meters out of them and publish them to various system over
various media. We do this currently by listening to notification on RPC,
but there's no obligation nor gain to do that, and squeezing it would be
a gain.
But the notification drivers being a list, nothing prevents you to still
send notification on the RPC either. :)

Julien Danjou
;; Free Software hacker ; freelance consultant
;; http://julien.danjou.info
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