Connect MQTT client to database and implement basic JSON parsing

app/mod_devices/models.py

@@ -18,12 +18,13 @@ class Recording(db.Model):
 
     def __init__(self, device_id, record_type,
                  record_value, recorded_at, raw_json):
-        self.device_id = device_id
-        self.record_type = record_type
-        self.record_value = record_value
-        self.recorded_at = recorded_at
+        self.device_id = int(device_id)
+        self.record_type = int(record_type)
+        self.record_value = str(record_value)
+        self.recorded_at = datetime.fromtimestamp(int(recorded_at))
         self.received_at = datetime.utcnow()
         self.raw_record = raw_json
 
     def __repr__(self):
-        return '<Recording %r>' % self.recorded_at
+        return '<Recording (value=%s, recorded_at=%s)>' % (
+            self.record_value, self.recorded_at)

app/mod_devices/mqtt_client.py

@@ -1,4 +1,5 @@
-from datetime import datetime
+import sys
+import json
 from flask_mqtt import Mqtt
 from .models import Recording
 from . import db
@@ -24,7 +25,7 @@ def tear_down_mqtt():
 @mqtt.on_connect()
 def handle_connect(client, userdata, flags, rc):
     print('MQTT client connected')
-    mqtt.subscribe('topic/state')
+    mqtt.subscribe('device/+')
 
 
 @mqtt.on_disconnect()
@@ -37,7 +38,39 @@ def handle_subscribe(client, userdata, mid, granted_qos):
 
 
 def handle_mqtt_message(client, userdata, message):
-    recording = Recording(1, 1, "315", datetime.utcnow(), "{}")
+    print("Received message!")
+    print("Topic: " + message.topic)
+    print("Payload: " + message.payload.decode())
+    try:
+        # If type is JSON
+        recording = parse_json_message(message.topic, message.payload.decode())
         db.session.add(recording)
         db.session.commit()
-    print(message.payload.decode())
+        print(recording)
+    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, json_msg["record_type"],
+                         json_msg["record_value"], json_msg["recorded_at"],
+                         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")