Replaces direct use of aiokafka with osm_common message bus in agent and
lcmclient

Changes config handling to comply with the way it is handled in other modules,
by using a config file and overriding it with env vars.

Adds unit tests for message_bus_client.

Mon client remains using aiokafka directly, as there is no support yet for
auto_offset_reset configuration in osm_common.

Change-Id: I99615287cc934ce310105e86544a6bfe26bc0673
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>
diff --git a/osm_policy_module/common/common_db_client.py b/osm_policy_module/common/common_db_client.py
index 2be3693..5731155 100644
--- a/osm_policy_module/common/common_db_client.py
+++ b/osm_policy_module/common/common_db_client.py
@@ -21,18 +21,21 @@
 # For those usages not covered by the Apache License, Version 2.0 please
 # contact: bdiaz@whitestack.com or glavado@whitestack.com
 ##
-from osm_common import dbmongo
+from osm_common import dbmongo, dbmemory
 
 from osm_policy_module.core.config import Config
 from osm_policy_module.core.exceptions import VdurNotFound
 
 
 class CommonDbClient:
-    def __init__(self):
-        cfg = Config.instance()
-        self.common_db = dbmongo.DbMongo()
-        self.common_db.db_connect({'uri': cfg.OSMPOL_DATABASE_URI,
-                                   'name': 'osm'})
+    def __init__(self, config: Config):
+        if config.get('database', 'driver') == "mongo":
+            self.common_db = dbmongo.DbMongo()
+        elif config.get('database', 'driver') == "memory":
+            self.common_db = dbmemory.DbMemory()
+        else:
+            raise Exception("Unknown database driver {}".format(config.get('section', 'driver')))
+        self.common_db.db_connect(config.get("database"))
 
     def get_vnfr(self, nsr_id: str, member_index: int):
         vnfr = self.common_db.get_one("vnfrs",
@@ -65,3 +68,6 @@
                 return vdur
         raise VdurNotFound('vdur not found for nsr-id %s, member_index %s and vdur_name %s', nsr_id, member_index,
                            vdur_name)
+
+    def create_nslcmop(self, nslcmop):
+        self.common_db.create("nslcmops", nslcmop)
diff --git a/osm_policy_module/common/lcm_client.py b/osm_policy_module/common/lcm_client.py
index 05378d7..2efa241 100644
--- a/osm_policy_module/common/lcm_client.py
+++ b/osm_policy_module/common/lcm_client.py
@@ -28,22 +28,17 @@
 import time
 import uuid
 
-from aiokafka import AIOKafkaProducer
-from osm_common import dbmongo
-
+from osm_policy_module.common.common_db_client import CommonDbClient
+from osm_policy_module.common.message_bus_client import MessageBusClient
 from osm_policy_module.core.config import Config
 
 log = logging.getLogger(__name__)
 
 
 class LcmClient:
-    def __init__(self, loop=None):
-        cfg = Config.instance()
-        self.kafka_server = '{}:{}'.format(cfg.OSMPOL_MESSAGE_HOST,
-                                           cfg.OSMPOL_MESSAGE_PORT)
-        self.common_db = dbmongo.DbMongo()
-        self.common_db.db_connect({'uri': cfg.OSMPOL_DATABASE_URI,
-                                   'name': 'osm'})
+    def __init__(self, config: Config, loop=None):
+        self.db_client = CommonDbClient(config)
+        self.msg_bus = MessageBusClient(config)
         if not loop:
             loop = asyncio.get_event_loop()
         self.loop = loop
@@ -51,19 +46,9 @@
     async def scale(self, nsr_id: str, scaling_group_name: str, vnf_member_index: int, action: str):
         log.debug("scale %s %s %s %s", nsr_id, scaling_group_name, vnf_member_index, action)
         nslcmop = self._generate_nslcmop(nsr_id, scaling_group_name, vnf_member_index, action)
-        self.common_db.create("nslcmops", nslcmop)
+        self.db_client.create_nslcmop(nslcmop)
         log.info("Sending scale action message: %s", json.dumps(nslcmop))
-        producer = AIOKafkaProducer(loop=self.loop,
-                                    bootstrap_servers=self.kafka_server,
-                                    key_serializer=str.encode,
-                                    value_serializer=str.encode)
-        await producer.start()
-        try:
-            # Produce message
-            await producer.send_and_wait("ns", key="scale", value=json.dumps(nslcmop))
-        finally:
-            # Wait for all pending messages to be delivered or expire.
-            await producer.stop()
+        await self.msg_bus.aiowrite("ns", "scale", nslcmop)
 
     def _generate_nslcmop(self, nsr_id: str, scaling_group_name: str, vnf_member_index: int, action: str):
         log.debug("_generate_nslcmop %s %s %s %s", nsr_id, scaling_group_name, vnf_member_index, action)
diff --git a/osm_policy_module/common/message_bus_client.py b/osm_policy_module/common/message_bus_client.py
new file mode 100644
index 0000000..ea5095d
--- /dev/null
+++ b/osm_policy_module/common/message_bus_client.py
@@ -0,0 +1,72 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2018 Whitestack, LLC
+# *************************************************************
+
+# This file is part of OSM Monitoring module
+# All Rights Reserved to Whitestack, LLC
+
+# 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.
+
+# For those usages not covered by the Apache License, Version 2.0 please
+# contact: bdiaz@whitestack.com or glavado@whitestack.com
+##
+import asyncio
+from typing import List, Callable
+
+from osm_common import msgkafka, msglocal
+
+from osm_policy_module.core.config import Config
+
+
+class MessageBusClient:
+    def __init__(self, config: Config, loop=None):
+        if config.get('message', 'driver') == "local":
+            self.msg_bus = msglocal.MsgLocal()
+        elif config.get('message', 'driver') == "kafka":
+            self.msg_bus = msgkafka.MsgKafka()
+        else:
+            raise Exception("Unknown message bug driver {}".format(config.get('section', 'driver')))
+        self.msg_bus.connect(config.get('message'))
+        if not loop:
+            loop = asyncio.get_event_loop()
+        self.loop = loop
+
+    async def aioread(self, topics: List[str], callback: Callable = None, **kwargs):
+        """
+        Retrieves messages continuously from bus and executes callback for each message consumed.
+        :param topics: List of message bus topics to consume from.
+        :param callback: Async callback function to be called for each message received.
+        :param kwargs: Keyword arguments to be passed to callback function.
+        :return: None
+        """
+        await self.msg_bus.aioread(topics, self.loop, aiocallback=callback, **kwargs)
+
+    async def aiowrite(self, topic: str, key: str, msg: dict):
+        """
+        Writes message to bus.
+        :param topic: Topic to write to.
+        :param key: Key to write to.
+        :param msg: Dictionary containing message to be written.
+        :return: None
+        """
+        await self.msg_bus.aiowrite(topic, key, msg, self.loop)
+
+    async def aioread_once(self, topic: str):
+        """
+        Retrieves last message from bus.
+        :param topic: topic to retrieve message from.
+        :return: tuple(topic, key, message)
+        """
+        result = await self.msg_bus.aioread(topic, self.loop)
+        return result
diff --git a/osm_policy_module/common/mon_client.py b/osm_policy_module/common/mon_client.py
index 5124ed5..76a6f52 100644
--- a/osm_policy_module/common/mon_client.py
+++ b/osm_policy_module/common/mon_client.py
@@ -36,10 +36,9 @@
 
 
 class MonClient:
-    def __init__(self, loop=None):
-        cfg = Config.instance()
-        self.kafka_server = '{}:{}'.format(cfg.OSMPOL_MESSAGE_HOST,
-                                           cfg.OSMPOL_MESSAGE_PORT)
+    def __init__(self, config: Config, loop=None):
+        self.kafka_server = '{}:{}'.format(config.get('message', 'host'),
+                                           config.get('message', 'port'))
         if not loop:
             loop = asyncio.get_event_loop()
         self.loop = loop