Added support for multiple listeners on multiple servers and topics for general-purpose messaging on the MQTT backend

platypush/backend/mqtt.py

@@ -5,6 +5,7 @@ import threading
 from platypush.backend import Backend
 from platypush.context import get_plugin
 from platypush.message import Message
+from platypush.message.event.mqtt import MQTTMessageEvent
 from platypush.message.request import Request
 from platypush.utils import set_thread_name
 
@@ -14,15 +15,22 @@ class MqttBackend(Backend):
     Backend that reads messages from a configured MQTT topic (default:
     ``platypush_bus_mq/<device_id>``) and posts them to the application bus.
 
+    Triggers:
+
+        * :class:`platypush.message.event.mqtt.MQTTMessageEvent` when a new
+            message is received on one of the custom listeners
+
     Requires:
 
         * **paho-mqtt** (``pip install paho-mqtt``)
     """
 
-    def __init__(self, host, port=1883, topic='platypush_bus_mq', tls_cafile=None,
-                 tls_certfile=None, tls_keyfile=None,
+    _default_mqtt_port = 1883
+
+    def __init__(self, host, port=_default_mqtt_port, topic='platypush_bus_mq',
+                 tls_cafile=None, tls_certfile=None, tls_keyfile=None,
                  tls_version=None, tls_ciphers=None, username=None,
-                 password=None, *args, **kwargs):
+                 password=None, listeners=None, *args, **kwargs):
         """
         :param host: MQTT broker host
         :type host: str
@@ -53,6 +61,15 @@ class MqttBackend(Backend):
 
         :param password: Specify it if the MQTT server requires authentication (default: None)
         :type password: str
+
+        :param listeners: If specified then the MQTT backend will also listen for
+            messages on the additional configured message queues. This parameter
+            is a list of maps where each item supports the same arguments passed
+            to the main backend configuration (host, port, topic, password etc.).
+            Note that the message queue configured on the main configuration
+            will expect valid Platypush messages that then can execute, while
+            message queues registered to the listeners will accept any message.
+        :type listeners: list[dict]
         """
 
         super().__init__(*args, **kwargs)
@@ -63,6 +80,7 @@ class MqttBackend(Backend):
         self.username = username
         self.password = password
         self._client = None
+        self._listeners = []
 
         self.tls_cafile = os.path.abspath(os.path.expanduser(tls_cafile)) \
             if tls_cafile else None
@@ -75,6 +93,7 @@ class MqttBackend(Backend):
 
         self.tls_version = tls_version
         self.tls_ciphers = tls_ciphers
+        self.listeners_conf = listeners or []
 
 
     def send_message(self, msg):
@@ -90,6 +109,60 @@ class MqttBackend(Backend):
         except Exception as e:
             self.logger.exception(e)
 
+    def _initialize_listeners(self, listeners_conf):
+        import paho.mqtt.client as mqtt
+
+        def listener_thread(client, host, port):
+            client.connect(host, port, 60)
+            client.loop_forever()
+
+        def on_connect(topic):
+            def handler(client, userdata, flags, rc):
+                client.subscribe(topic)
+            return handler
+
+        def on_message(client, userdata, msg):
+            data = msg.payload
+            try:
+                data = data.decode('utf-8')
+                data = json.loads(data)
+            except:
+                pass
+
+            self.bus.post(MQTTMessageEvent(host=client._host, port=client._port,
+                                           topic=msg.topic, msg=data))
+
+        for i, listener in enumerate(listeners_conf):
+            host = listener.get('host')
+            port = listener.get('port', self._default_mqtt_port)
+            topic = listener.get('topic')
+            username = listener.get('username')
+            password = listener.get('password')
+            tls_cafile = listener.get('tls_cafile')
+
+            if not host or not topic:
+                self.logger.warning('No host nor topic specified for listener ' +
+                                    'n.{}'.format(i+1))
+                continue
+
+            client = mqtt.Client()
+            client.on_connect = on_connect(topic)
+            client.on_message = on_message
+
+            if username and password:
+                client.username_pw_set(username, password)
+
+            if tls_cafile:
+                client.tls_set(ca_certs=tls_cafile,
+                               certfile=listener.get('tls_certfile'),
+                               keyfile=listener.get('tls_keyfile'),
+                               tls_version=listener.get('tls_version'),
+                               ciphers=listener.get('tls_ciphers'))
+
+            threading.Thread(target=listener_thread, kwargs = {
+                'client': client, 'host': host, 'port': port }).start()
+
+
     def run(self):
         def on_connect(client, userdata, flags, rc):
             client.subscribe(self.topic)
@@ -144,6 +217,7 @@ class MqttBackend(Backend):
         self.logger.info('Initialized MQTT backend on host {}:{}, topic {}'.
                      format(self.host, self.port, self.topic))
 
+        self._initialize_listeners(self.listeners_conf)
         self._client.loop_forever()
 
     def stop(self):
@@ -153,4 +227,14 @@ class MqttBackend(Backend):
             self._client.loop_stop()
             self._client = None
 
+        for listener in self._listeners:
+            try:
+                listener.loop_stop()
+            except Exception as e:
+                self.logger.warning('Could not stop listener ' +
+                                    '{host}:{port}: {error}'.format(
+                                        host=listener._host, port=listener._port,
+                                        error=str(e)))
+
+
 # vim:sw=4:ts=4:et:

platypush/message/event/mqtt.py

@@ -0,0 +1,15 @@
+from platypush.message.event import Event
+
+
+class MQTTMessageEvent(Event):
+    """
+    MQTT message event object. Fired when :mod:`platypush.backend.mqtt` receives
+    a new event.
+    """
+
+    def __init__(self, msg, host=None, port=None, topic=None, *args, **kwargs):
+        super().__init__(msg=msg, host=host, port=port, topic=topic,
+                         *args, **kwargs)
+
+
+# vim:sw=4:ts=4:et: