Define self.client in MessagingCore

Currently self.client is referenced within MessagingCore,
but no definition is made in its constructor. Additionally
self.client is defined in children classes of MessagingCore.
This patchset defines self.client in the constructor of
MessagingCore and removes the redefinition in its children.

-self.client lazily loaded

Co-Authored-By: v-francoise <Vincent.FRANCOISE@b-com.com>
Change-Id: I14525a175bf1ebde3d2636024ad2f2219c79d6e1
Closes-Bug: #1521636

watcher/decision_engine/rpcapi.py

@@ -19,10 +19,10 @@
 
 from oslo_config import cfg
 from oslo_log import log
-import oslo_messaging as om
 
 from watcher.common import exception
 from watcher.common.messaging.messaging_core import MessagingCore
+from watcher.common.messaging.notification_handler import NotificationHandler
 from watcher.common import utils
 from watcher.decision_engine.manager import decision_engine_opt_group
 from watcher.decision_engine.manager import WATCHER_DECISION_ENGINE_OPTS
@@ -40,22 +40,16 @@ class DecisionEngineAPI(MessagingCore):
     def __init__(self):
         super(DecisionEngineAPI, self).__init__(
             CONF.watcher_decision_engine.publisher_id,
-            CONF.watcher_decision_engine.topic_control,
-            CONF.watcher_decision_engine.topic_status,
+            CONF.watcher_decision_engine.conductor_topic,
+            CONF.watcher_decision_engine.status_topic,
             api_version=self.API_VERSION,
         )
-
-        transport = om.get_transport(CONF)
-        target = om.Target(
-            topic=CONF.watcher_decision_engine.topic_control,
-            version=self.API_VERSION,
-        )
-        self.client = om.RPCClient(transport, target,
-                                   serializer=self.serializer)
+        self.handler = NotificationHandler(self.publisher_id)
+        self.status_topic_handler.add_endpoint(self.handler)
 
     def trigger_audit(self, context, audit_uuid=None):
         if not utils.is_uuid_like(audit_uuid):
             raise exception.InvalidUuidOrName(name=audit_uuid)
 
-        return self.client.call(
+        return self.conductor_client.call(
             context.to_dict(), 'trigger_audit', audit_uuid=audit_uuid)