Do not wait for MessageHandlingServer

Previously oslo.messaging's MessageHandlingServer
was used as as a murano-engine service in service launcher.
As a result it's wait() method was called. But after recent
changes it's wait method is supposed to be call only
after stop() to wait for graceful message processing to end.
As a result a warning was printed that stop() didn't finish
after 30 sec from wait() invocation (because it was never called).

This commit adds EngineService service implementation
that has its own wait() and encapsulates MessageHandlingServer
instance.

Change-Id: Ie553e0b27cc1c261b963907b4f12f89795b99a12
Closes-Bug: #1521087

murano/cmd/engine.py

@@ -48,7 +48,7 @@ def main():
 
         logging.setup(CONF, 'murano')
         launcher = service.ServiceLauncher(CONF)
-        launcher.launch_service(engine.get_rpc_service())
+        launcher.launch_service(engine.EngineService())
 
         launcher.wait()
     except RuntimeError as e:

murano/common/engine.py

@@ -23,6 +23,7 @@ from oslo_log import log as logging
 import oslo_messaging as messaging
 from oslo_messaging import target
 from oslo_serialization import jsonutils
+from oslo_service import service
 
 from murano.common import auth_utils
 from murano.common.helpers import token_sanitizer
@@ -42,7 +43,6 @@ from murano.policy import model_policy_enforcer as enforcer
 
 CONF = cfg.CONF
 
-RPC_SERVICE = None
 PLUGIN_LOADER = None
 
 LOG = logging.getLogger(__name__)
@@ -50,20 +50,33 @@ LOG = logging.getLogger(__name__)
 eventlet.debug.hub_exceptions(False)
 
 
-def _prepare_rpc_service(server_id):
-    endpoints = [TaskProcessingEndpoint()]
+# noinspection PyAbstractClass
+class EngineService(service.Service):
+    def __init__(self):
+        super(EngineService, self).__init__()
+        self.server = None
 
-    transport = messaging.get_transport(CONF)
-    s_target = target.Target('murano', 'tasks', server=server_id)
-    return messaging.get_rpc_server(transport, s_target, endpoints, 'eventlet')
+    def start(self):
+        endpoints = [TaskProcessingEndpoint()]
 
+        transport = messaging.get_transport(CONF)
+        s_target = target.Target('murano', 'tasks', server=str(uuid.uuid4()))
+        self.server = messaging.get_rpc_server(
+            transport, s_target, endpoints, 'eventlet')
+        self.server.start()
+        super(EngineService, self).start()
 
-def get_rpc_service():
-    global RPC_SERVICE
+    def stop(self, graceful=False):
+        if self.server:
+            self.server.stop()
+            if graceful:
+                self.server.wait()
+        super(EngineService, self).stop()
 
-    if RPC_SERVICE is None:
-        RPC_SERVICE = _prepare_rpc_service(str(uuid.uuid4()))
-    return RPC_SERVICE
+    def reset(self):
+        if self.server:
+            self.server.reset()
+        super(EngineService, self).reset()
 
 
 def get_plugin_loader():