Disable pubsub when getting nb_api in external apps

The pubsub creates different problems, and every external app
specifically disables it before getting the nb_api instance.
We should hide this behaviour inside the get_instance method.
Also, I called the argument is_external_app as in the future we may want
to add more behavioural differences between the cases.

Change-Id: I25a55737351f8fe14bddafa7c78e60fe096db43e

dragonflow/cli/df_db.py

@@ -179,7 +179,7 @@ def add_object_from_json(json_str, table):
     :param table: table name where object should be added
     :return: None
     """
-    nb_api = api_nb.NbApi.get_instance(False)
+    nb_api = api_nb.NbApi.get_instance(False, True)
     try:
         model = model_framework.get_model(table)
     except KeyError:

dragonflow/cmd/eventlet/df_metadata_service.py

@@ -81,8 +81,7 @@ def main():
     config.init(sys.argv[1:])
     config.setup_logging()
     environment_setup()
-    cfg.CONF.set_override('enable_df_pub_sub', False, group='df')
-    nb_api = api_nb.NbApi.get_instance(False)
+    nb_api = api_nb.NbApi.get_instance(False, True)
     service_instance = metadata_service.DFMetadataProxyHandler(
             cfg.CONF, nb_api)
     df_service.register_service(

dragonflow/controller/df_bgp_service.py

@@ -165,10 +165,7 @@ class BGPService(service.Service):
 
 def main():
     df_config.init(sys.argv)
-    # BGP dynamic route is not a service that needs real time response.
-    # So disable pubsub here and use period task to do BGP job.
-    cfg.CONF.set_override('enable_df_pub_sub', False, group='df')
-    nb_api = api_nb.NbApi.get_instance(False)
+    nb_api = api_nb.NbApi.get_instance(False, True)
     server = BGPService(nb_api)
     df_service.register_service('df-bgp-service', nb_api, server)
     service.launch(cfg.CONF, server).wait()

dragonflow/controller/df_publisher_service.py

@@ -147,8 +147,7 @@ class PublisherService(object):
 
 def main():
     df_config.init(sys.argv)
-    cfg.CONF.set_override('enable_df_pub_sub', False, group='df')
-    nb_api = api_nb.NbApi.get_instance(False)
+    nb_api = api_nb.NbApi.get_instance(False, True)
     service = PublisherService(nb_api)
     df_service.register_service('df-publisher-service', nb_api, service)
     service.initialize()

dragonflow/db/api_nb.py

@@ -60,15 +60,20 @@ class NbApi(object):
             self.pub_sub_use_multiproc = cfg.CONF.df.pub_sub_use_multiproc
 
     @staticmethod
-    def get_instance(is_neutron_server):
+    def get_instance(is_neutron_server, is_external_app=False):
         global _nb_api
         if _nb_api is None:
             nb_driver = df_utils.load_driver(
                 cfg.CONF.df.nb_db_class,
                 df_utils.DF_NB_DB_DRIVER_NAMESPACE)
+            # Do not use pubsub for external apps - this causes issues with
+            # threads and other issues.
+            use_pubsub = cfg.CONF.df.enable_df_pub_sub
+            if is_external_app:
+                use_pubsub = False
             nb_api = NbApi(
                 nb_driver,
-                use_pubsub=cfg.CONF.df.enable_df_pub_sub,
+                use_pubsub=use_pubsub,
                 is_neutron_server=is_neutron_server)
             nb_api.initialize(db_ip=cfg.CONF.df.remote_db_ip,
                               db_port=cfg.CONF.df.remote_db_port)