Projects will need to do e.g.

  -- nova.config:

  from nova.openstack.common.messaging import transport

  TRANSPORT_DRIVER = None


  def parse_args(argv, ...):
      transport.set_defaults(control_exchange='nova')
      cfg.CONF(...)
      TRANSPORT_DRIVER = transport.get_transport(cfg.CONF)

  -- nova.scheduler.rpcapi:

  from oslo.config import cfg

  from nova import config
  from nova.openstack.common.messaging.rpc import client
  from nova.openstack.common.messaging import target

  CONF = cfg.CONF


  class SchedulerAPI(client.RPCClient):

      def __init__(self):
          target = target.Target(topic=CONF.scheduler_topic, version='2.0')
          super(SchedulerAPI, self).__init__(config.TRANSPORT_DRIVER, target)

      ....

      def select_hosts(self, ctxt, request_spec, filter_properties):
          # FIXME(markmc): ctxt
          cctxt = self.prepare(version='2.6')
          return ctxt.call('select_hosts',
                           request_spec=request_spec,
                           filter_properties=filter_properties)

  -- nova.service:

  from nova import baserpc
  from nova import config
  from nova.openstack.common.messaging.rpc import server as rpcserver
  from nova.openstack.common.messaging.rpc import target

      def start(self):
          ...
          target = target.Target(topic=self.topic, self.host)

          base_rpc = baserpc.BaseRPCAPI(self.service_name, backdoor_port)

          self.rpcserver = rpcserver.EventletRPCServer(config.TRANSPORT_DRIVER,
                                                       target,
                                                       [self.manager, base_rpc])

          LOG.debug(_("Starting RPC server for %(topic)s on %(host)s") %
                    dict(topic=self.topic, host=self.host))

          self.rpcserver.start()

          ...
          self.rpcserver.stop()
          self.rpcserver.wait()