Add an interface and config options for modular switch

Add the an interface (base class) for modular switch.
Also add the relevant configuration options.

Change-Id: I79675aa720cf60ae599b13188b85ae26ea6d2a84

dragonflow/common/utils.py

@@ -32,6 +32,7 @@ from dragonflow import version
 DF_PUBSUB_DRIVER_NAMESPACE = 'dragonflow.pubsub_driver'
 DF_NB_DB_DRIVER_NAMESPACE = 'dragonflow.nb_db_driver'
 DF_NEUTRON_NOTIFIER_DRIVER_NAMESPACE = 'dragonflow.neutron_notifier_driver'
+DF_SWITCH_BACKEND_DRIVER_NAMESPACE = 'dragonflow.switch_backend_driver'
 LOG = logging.getLogger(__name__)
 
 

dragonflow/conf/df_common_params.py

@@ -69,6 +69,9 @@ df_opts = [
     cfg.StrOpt('neutron_notifier',
                default='nb_api_neutron_notifier_driver',
                help=_('Notifier for the Dragonflow controller events')),
+    cfg.StrOpt('switch_backend',
+               default='vswitch_backend_driver',
+               help=_('Backend switch drivers to use')),
     cfg.ListOpt('publishers_ips',
                 default=['$local_ip'],
                 help=_('List of the Neutron Server Publisher IPs.')),

dragonflow/switch/drivers/df_switch_driver.py

@@ -0,0 +1,51 @@
+# Copyright (c) 2018 OpenStack Foundation
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+import abc
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class DfSwitchDriver(object):
+    def __init__(self, nb_api):
+        super(DfSwitchDriver, self).__init__()
+        self.db_change_callback = None
+        self.nb_api = nb_api
+
+    def initialize(self, db_change_callback):
+        self.db_change_callback = db_change_callback
+
+    @abc.abstractmethod
+    def start(self):
+        """Start running the switch backend"""
+
+    @abc.abstractmethod
+    def stop(self):
+        """Stop the switch backend"""
+
+    @abc.abstractmethod
+    def switch_sync_started(self):
+        """Callback on switch sync start"""
+
+    @abc.abstractmethod
+    def switch_sync_finished(self):
+        """Callback on switch sync done"""
+
+    def sync_ignore_models(self):
+        """Which models to ignore on sync
+        :returns list of model names
+        """
+        return []