Notification and CDM partial update

In this changeset, I implemented the notification handling (Rx only)
system for consuming incoming notifications, more especially the Nova
ones. The notifications handlers also contain the logic which
incrementally updates the Compute model.

Change-Id: Ia036a5a2be6caa64b7f180de38821b57c624300c
Partially-implements: blueprint cluster-model-objects-wrapper

watcher/decision_engine/model/notification/base.py

@@ -0,0 +1,51 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2016 b<>com
+#
+# Authors: Vincent FRANCOISE <Vincent.FRANCOISE@b-com.com>
+#
+# 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
+
+from oslo_log import log
+
+from watcher.common import rpc
+
+LOG = log.getLogger(__name__)
+
+
+@six.add_metaclass(abc.ABCMeta)
+class NotificationEndpoint(object):
+
+    def __init__(self, collector):
+        super(NotificationEndpoint, self).__init__()
+        self.collector = collector
+        self._notifier = None
+
+    @abc.abstractproperty
+    def filter_rule(self):
+        """Notification Filter"""
+        raise NotImplementedError()
+
+    @property
+    def cluster_data_model(self):
+        return self.collector.cluster_data_model
+
+    @property
+    def notifier(self):
+        if self._notifier is None:
+            self._notifier = rpc.get_notifier('decision-engine')
+
+        return self._notifier