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

Doug Hellmann doug.hellmann at dreamhost.com
Fri Apr 26 11:19:47 UTC 2013

On Friday, April 26, 2013, Julien Danjou wrote:

> On Fri, Apr 26 2013, Doug Hellmann wrote:
> > After thinking about this a little more I realized that this doesn't
> solve
> > the problem of allowing one service to talk to another on a separate
> > "exchange." If that's still something we want to do, we need another
> > argument passed to the ConnectionFactory to represent that exchange
> > explicitly (I know we need another name, but until we come up with one
> I'll
> > stick with "exchange"). The default can come from the config, but callers
> > like ceilometer need a way to specify an alternative value.
> >
> > Do we care if the exchange for a service is not on the same host? Do we
> > need to allow users to provide different host/port settings for every
> > exchange?
> Yes, that's why I thought we would include the control exchange as part
> of a connection URL. That would be an abstraction detail for AMQP, where
> url would be something like amqp://localhost:3456/mycontrolexchange.

I definitely like the idea of using a URL instead of the multiple params we
have now, but we will need a way to migrate or otherwise support old

The real challenge, in my mind, is how to know which URL to use for a given
connection. If we have several, what values are part of the lookup key?

> For example, in my envisioned Ceilometer case we would just have to
> specify the
> ceilometer URL as amqp://host:port/ceilometer to be able to use
> rpc.call().
> For our current notification consuming, we sould use an URL for each
> notification listener for each project: amqp://host:port/nova,
> amqp://host:port/glance, etc.
> I'm pretty confident we can map this URL scheme to ZMQ (and its
> matchmaker) and includes all its components in the Connection as
> discriminating.
> --
> Julien Danjou
> -- Free Software hacker - freelance consultant
> -- http://julien.danjou.info
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