Add some notes

doc/messaging/changes.txt

@@ -4,31 +4,30 @@ Projects will need to do e.g.
 
   -- nova.config:
 
-  from nova.openstack.common.messaging import transport
+  from oslo import messaging
 
   TRANSPORT_DRIVER = None
 
 
   def parse_args(argv, ...):
-      transport.set_defaults(control_exchange='nova')
+      messaging.set_transport_defaults(control_exchange='nova')
       cfg.CONF(...)
       TRANSPORT_DRIVER = transport.get_transport(cfg.CONF)
 
   -- nova.scheduler.rpcapi:
 
   from oslo.config import cfg
+  from oslo import messaging
 
   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):
+  class SchedulerAPI(messaging.RPCClient):
 
       def __init__(self):
-          target = target.Target(topic=CONF.scheduler_topic, version='2.0')
+          target = messaging.Target(topic=CONF.scheduler_topic, version='2.0')
           super(SchedulerAPI, self).__init__(config.TRANSPORT_DRIVER, target)
 
       ....
@@ -42,20 +41,21 @@ Projects will need to do e.g.
 
   -- nova.service:
 
+  from oslo import messaging
+
   from nova import baserpc
   from nova import config
-  from nova.openstack.common.messaging import eventlet
-  from nova.openstack.common.messaging import target
 
       def start(self):
           ...
-          target = target.Target(topic=self.topic, self.server)
+          target = messaging.Target(topic=self.topic, self.server)
 
           base_rpc = baserpc.BaseRPCAPI(self.service_name, backdoor_port)
 
-          self.rpcserver = eventlet.EventletRPCServer(config.TRANSPORT_DRIVER,
-                                                      target,
-                                                      [self.manager, base_rpc])
+          self.rpcserver = messaging.get_rpc_server(config.TRANSPORT_DRIVER,
+                                                    target,
+                                                    [self.manager, base_rpc],
+                                                    executor='eventlet')
 
           LOG.debug(_("Starting RPC server for %(topic)s on %(server)s") %
                     dict(topic=self.topic, host=self.server))
@@ -65,3 +65,41 @@ Projects will need to do e.g.
           ...
           self.rpcserver.stop()
           self.rpcserver.wait()
+
+
+== notifier ==
+
+Will need e.g.
+
+  from oslo import messaging
+
+  from nova import config
+
+  def get_notifier(host=None):
+      global _NOTIFIER
+      if _NOTIFIER is None:
+          _NOTIFIER = messaging.Notifier(cfg.CONF,
+                                         'compute.%s' % (host or cfg.host,
+                                         transport=config.TRANSPORT_DRIVER)
+      return _NOTIFIER
+
+
+  def notify_about_instance_usage(context, instance, event, ..., host=None):
+      usage_info = notifications.info_from_instance(context, instance, ...)
+
+      notifier = get_notifier(host)
+      notify = notifier.error if event.endswith("error") else notifier.info
+      notify(context, 'compute.instance.%s' % event, usage_info)
+
+Misc changes vs openstack.common.notifier.api:
+
+  - jsonutil.to_primitive(payload, convert_instances=True) is no longer called,
+    I'm figuring that you should supply a serializer instead
+  - need to construct a Notifier object, there is no global notifier state
+  - you'll need a Notifier object per-service, since publisher_id is an object
+    attribute
+  - publisher_id() has been removed, so you do 'service.host' manually
+  - the log levels aren't exposed by the API, instead use the info() etc.
+    methods on the Notifier class
+  - notifiy_decorator has been removed, see:
+      https://github.com/markmc/oslo-incubator/tree/oslo-messaging-notify-decorator

doc/messaging/notes.txt

@@ -1,6 +1,14 @@
 
 TODO:
 
+  - apps need to be able to register backwards compat aliases for
+    entry point names
+
+      get_transport(conf, driver_aliases={
+        'nova.openstack.common.rpc.impl_kombu': 'rabbit',
+        'nova.openstack.common.rpc.impl_qpid: 'qpid',
+        'nova.openstack.common.rpc.impl_zmq: 'zmq'})
+
   - we need some way for the dispatcher to take the incoming
     context dict and instantiate a user-supplied request context
     object with it