How Can I Resolve MQTT Socket Errors and Optimize My Django API Design?

Hi everyone,

I'm developing a Django REST API that integrates with an MQTT broker to manage home device settings. The API connects to the broker on-demand to fetch real-time device settings without using a database or cache. However, I occasionally encounter socket errors when connecting to the broker. Additionally, I'm evaluating if this real-time approach is optimal or if storing MQTT payloads in a database like InfluxDB might be a better solution.

Here's a brief rundown of the workflow:

• When a user authenticates, the API connects to the MQTT broker, subscribes to a device-specific topic, and awaits the current settings.
• The settings are returned as the API response if received in time; otherwise, an error is produced.

The following is the API endpoint code:

PYTHONCopied
class ProductSettingsView(GenericAPIView):
    permission_classes = [IsAuthenticated]
    serializer_class = ProductSerializer

    def post(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        if serializer.is_valid(raise_exception=True):
            product_id = serializer.validated_data['product_id']
            product = ALL_POMP_AO_PRODUCTS.get(owner_id=self.request.user.id, id=product_id)

        user = self.request.user
        if not user:
            raise exceptions.BadRequest(
                {'detail': _("User doesn't exist"), "code": "user_do_not_exist"}
            )

        if not product:
            raise exceptions.BadRequest(
                {"detail": _("User/Product relation violation"), "code": "invalid_relation"}
            )

        try:
            certificate = Certificate.objects.get(client_id=user.id)
        except Certificate.DoesNotExist:
            raise exceptions.BadRequest(
                {"detail": _("Certificate doesn't exist"), "code": "certificate_do_not_exist"}
            )

        try:
            with MqttClient(user=str(user.uuid), certificate=certificate.certificate, key=certificate.key, product=product) as mqtt_client:
                message = mqtt_client.get_message()
                if message:
                    return Response(message, status=status.HTTP_200_OK)
                else:
                    return Response(
                        {"error": "Timeout or no message received"},
                        status=status.HTTP_504_GATEWAY_TIMEOUT
                    )
        except exceptions.BadRequest as e:
            return Response(e.detail, status=status.HTTP_400_BAD_REQUEST)

And here is the MQTT client code:

PYTHONCopied
class MqttProduct:
    def __init__(self, user, certificate, key, product):
        self.user_name = user
        self.product = product
        self.certfile = certificate
        self.keyfile = key

        self.ssl_context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
        self.ssl_context.load_cert_chain(certfile=self.certfile, keyfile=self.keyfile)
        self.ssl_context.load_verify_locations(cafile=ENV.path("MQTT_SERVER_CA"))

        self.mqtt_client = mqtt.Client(client_id=self.user_name, clean_session=True)
        self.mqtt_client.tls_set_context(self.ssl_context)
        self.mqtt_client.on_connect = self.on_connect
        self.mqtt_client.on_message = self.on_message
        self.lock = threading.Condition()

    def on_connect(self, client, userdata, flags, rc):
        if rc == 0:
            print("Connected to broker")
            self.mqtt_client.subscribe(f"path/{self.product.name}/settings", qos=1)
        else:
            print("Failed to connect, return code %d\n", rc)

    def on_message(self, client, userdata, msg):
        with self.lock:
            # Process my message here
            self.lock.notify()

    def get_message(self):
        try:
            self.connection_ready = threading.Event()
            self.mqtt_client.connect(self.BROKER, self.BROKERPORT, 60)
            self.mqtt_client.loop_start()

            if not self.connection_ready.wait(timeout=10):  # Wait for connection
                print("Connection timeout")
                return None

            with self.lock:
                if not self.lock.wait(timeout=10):
                    print("Timeout waiting for message")
                    return None

            with self.lock:
                    return list(self.messages.values())

        except (Exception, ssl.SSLError) as e:
            logging.error(f"MQTT connection failed: {e}")
            raise exceptions.BadRequest(
                {
                    "detail": _("MQTT Connection Error"),
                   "code": "mqtt_connection_error"
                }
            )
        finally:
            self.stop()

I need help with the following questions:

1. What might be causing these intermittent socket errors despite using valid certificates and proper MQTT settings?
2. Is my approach of fetching device settings in real-time without caching or storing them suitable for this use case?
3. Would using a database like InfluxDB to store MQTT payloads improve system reliability and reduce connection issues?
4. What best practices should I consider when designing an API that communicates with an MQTT broker for real-time data?

I appreciate any advice or suggestions. Thanks for your help!