Encapsulate Mqtt client in a class

app/mod_devices/__init__.py

@@ -1,13 +1,14 @@
 import atexit
 from flask import Blueprint
-from .mqtt_client import tear_down_mqtt, setup_mqtt
+from .mqtt_client import MqttClient
 
 devices = Blueprint('devices', __name__)
+mqtt_client = MqttClient()
 
 
 # When app dies, stop mqtt connection
 def on_stop():
-    tear_down_mqtt()
+    mqtt_client.tear_down()
 
 
 atexit.register(on_stop)
@@ -21,4 +22,4 @@ def hello():
 
 @devices.record
 def on_blueprint_setup(setup_state):
-    setup_mqtt(setup_state.app)
+    mqtt_client.setup(setup_state.app)

app/mod_devices/mqtt_client.py

@@ -4,74 +4,78 @@ from flask_mqtt import Mqtt
 from .models import Recording
 from app import db, app
 
-mqtt = Mqtt()
+class MqttClient:
+    def __init__(self):
+        self.mqtt = Mqtt()
+        self.initialized = False
 
 
-# Mqtt setup
+    # Mqtt setup
-def setup_mqtt(app):
+    def setup(self, app):
-    mqtt.init_app(app)
+        if not self.initialized:
-    mqtt.client.on_message = handle_mqtt_message
+            self.mqtt.init_app(app)
-    mqtt.client.on_subscribe = handle_subscribe
+            self.mqtt.client.on_message = self.handle_mqtt_message
-    print('MQTT client initialized')
+            self.mqtt.client.on_subscribe = self.handle_subscribe
+            initialized = True
+
+            @self.mqtt.on_connect()
+            def handle_connect(client, userdata, flags, rc):
+                print('MQTT client connected')
+                self.mqtt.subscribe('device/+')
+
+            @self.mqtt.on_disconnect()
+            def handle_disconnect():
+                print('MQTT client disconnected')
+
+            print('MQTT client initialized')
 
 
-def tear_down_mqtt():
+    def tear_down(self):
-    mqtt.unsubscribe_all()
+        self.mqtt.unsubscribe_all()
-    if hasattr(mqtt, 'client') and mqtt.client is not None:
+        if hasattr(self.mqtt, 'client') and self.mqtt.client is not None:
-        mqtt.client.disconnect()
+            self.mqtt.client.disconnect()
-    print('MQTT client destroyed')
+        print('MQTT client destroyed')
 
 
-@mqtt.on_connect()
+    def handle_subscribe(self, client, userdata, mid, granted_qos):
-def handle_connect(client, userdata, flags, rc):
+        print('MQTT client subscribed')
-    print('MQTT client connected')
-    mqtt.subscribe('device/+')
 
 
-@mqtt.on_disconnect()
+    def handle_mqtt_message(self, client, userdata, message):
-def handle_disconnect():
+        print("Received message!")
-    print('MQTT client disconnected')
+        print("Topic: " + message.topic)
+        print("Payload: " + message.payload.decode())
+        try:
+            # If type is JSON
+            recording = self.parse_json_message(message.topic, message.payload.decode())
+            with app.app_context():
+                recording.save()
+        except ValueError:
+            print("ERROR!")
+            error_type, error_instance, traceback = sys.exc_info()
+            print("Type: " + str(error_type))
+            print("Instance: " + str(error_instance))
+            return
 
 
-def handle_subscribe(client, userdata, mid, granted_qos):
+    def parse_json_message(self, topic, payload) -> Recording:
-    print('MQTT client subscribed')
+        try:
+            json_msg = json.loads(payload)
+            device_id = self.get_device_id(topic)
+            return Recording(device_id=device_id,
+                             record_type=json_msg["record_type"],
+                             record_value=json_msg["record_value"],
+                             recorded_at=json_msg["recorded_at"],
+                             raw_json=json_msg)
+        except KeyError:
+            error_type, error_instance, traceback = sys.exc_info()
+            raise ValueError("JSON parsing failed! Key error: "
+                             + str(error_instance))
 
 
-def handle_mqtt_message(client, userdata, message):
+    def get_device_id(self, topic) -> int:
-    print("Received message!")
+        device_token, device_id = topic.split("/")
-    print("Topic: " + message.topic)
+        if device_token == "device":
-    print("Payload: " + message.payload.decode())
+            return int(device_id)
-    try:
+        else:
-        # If type is JSON
+            raise ValueError("Topic is in invalid format")
-        recording = parse_json_message(message.topic, message.payload.decode())
-        with app.app_context():
-            recording.save()
-    except ValueError:
-        print("ERROR!")
-        error_type, error_instance, traceback = sys.exc_info()
-        print("Type: " + str(error_type))
-        print("Instance: " + str(error_instance))
-        return
-
-
-def parse_json_message(topic, payload) -> Recording:
-    try:
-        json_msg = json.loads(payload)
-        device_id = get_device_id(topic)
-        return Recording(device_id=device_id,
-                         record_type=json_msg["record_type"],
-                         record_value=json_msg["record_value"],
-                         recorded_at=json_msg["recorded_at"],
-                         raw_json=json_msg)
-    except KeyError:
-        error_type, error_instance, traceback = sys.exc_info()
-        raise ValueError("JSON parsing failed! Key error: "
-                         + str(error_instance))
-
-
-def get_device_id(topic) -> int:
-    device_token, device_id = topic.split("/")
-    if device_token == "device":
-        return int(device_id)
-    else:
-        raise ValueError("Topic is in invalid format")