Use taskflow library for building and executing action plans

The aim of this patchset is to integrate taskflow in
the Watcher Applier. Taskflow will help us a lot to make
Action Plan execution easy, consistent, scalable and reliable.

DocImpact

Partially implements: blueprint use-taskflow

Change-Id: I903d6509d74a61ad64e1506b8a7156e6e91abcfb
Closes-Bug: #1535326
Closes-Bug: #1531912

watcher/applier/workflow_engine/base.py

@@ -0,0 +1,70 @@
+# -*- encoding: utf-8 -*-
+# Copyright (c) 2016 b<>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 watcher.applier.actions import factory
+from watcher.applier.messaging import event_types
+from watcher.common.messaging.events import event
+from watcher import objects
+
+
+@six.add_metaclass(abc.ABCMeta)
+class BaseWorkFlowEngine(object):
+    def __init__(self):
+        self._applier_manager = None
+        self._context = None
+        self._action_factory = factory.ActionFactory()
+
+    @property
+    def context(self):
+        return self._context
+
+    @context.setter
+    def context(self, c):
+        self._context = c
+
+    @property
+    def applier_manager(self):
+        return self._applier_manager
+
+    @applier_manager.setter
+    def applier_manager(self, a):
+        self._applier_manager = a
+
+    @property
+    def action_factory(self):
+        return self._action_factory
+
+    def notify(self, action, state):
+        db_action = objects.Action.get_by_uuid(self.context, action.uuid)
+        db_action.state = state
+        db_action.save()
+        ev = event.Event()
+        ev.type = event_types.EventTypes.LAUNCH_ACTION
+        ev.data = {}
+        payload = {'action_uuid': action.uuid,
+                   'action_state': state}
+        self.applier_manager.topic_status.publish_event(ev.type.name,
+                                                        payload)
+
+    @abc.abstractmethod
+    def execute(self, actions):
+        raise NotImplementedError()