Updating miniconf utility to use correlation data

miniconf.py

@@ -10,6 +10,7 @@ import asyncio
 import json
 import logging
 import sys
+import uuid
 
 from gmqtt import Client as MqttClient
 
@@ -33,28 +34,52 @@ class Miniconf:
             client: A connected MQTT5 client.
             prefix: The MQTT toptic prefix of the device to control.
         """
+        self.uuid = uuid.uuid1(prefix)
+        self.request_id = 0
         self.client = client
         self.prefix = prefix
         self.inflight = {}
         self.client.on_message = self._handle_response
         self.client.subscribe(f'{prefix}/response/#')
 
-    def _handle_response(self, _client, topic, payload, *_args, **_kwargs):
+    def _handle_response(self, _client, _topic, payload, _qos, properties):
         """Callback function for when messages are received over MQTT.
 
         Args:
             _client: The MQTT client.
-            topic: The topic that the message was received on.
+            _topic: The topic that the message was received on.
             payload: The payload of the message.
+            _qos: The quality-of-service level of the received packet
+            properties: A dictionary of properties associated with the message.
         """
-        if topic not in self.inflight:
-            # TODO use correlation_data to distinguish clients and requests
-            logger.warning('Unexpected response on topic: %s', topic)
+        # Extract corrleation data from the properties
+        try:
+            correlation_data = json.loads(properties['correlation_data'])
+        except (json.decoder.JSONDecodeError, KeyError):
+            logger.warning('Ignoring message with invalid correlation data')
             return
 
+        # Validate the correlation data.
+        try:
+            if correlation_data['id'] != self.uuid.hex:
+                logger.info('Ignoring correlation data for different ID')
+                return
+            pid = correlation_data['pid']
+        except KeyError:
+            logger.warning('Ignoring unknown correlation data: %s', correlation_data)
+            return
+
+        if pid not in self.inflight:
+            logger.warning('Unexpected pid: %s', pid)
+            return
+
+        try:
             response = json.loads(payload)
-        self.inflight[topic].set_result((response['code'], response['msg']))
-        del self.inflight[topic]
+            self.inflight[pid].set_result((response['code'], response['msg']))
+            del self.inflight[pid]
+        except json.decoder.JSONDecodeError:
+            logger.warning('Invalid response format: %s', payload)
+
 
     async def command(self, path, value):
         """Write the provided data to the specified path.
@@ -69,21 +94,30 @@ class Miniconf:
         """
         setting_topic = f'{self.prefix}/settings/{path}'
         response_topic = f'{self.prefix}/response/{path}'
-        if response_topic in self.inflight:
-            # TODO use correlation_data to distinguish clients and requests
-            raise NotImplementedError(
-                    'Only one in-flight message per topic is supported')
+
+        # Assign a unique identifier to this update request.
+        pid = self.request_id
+        self.request_id += 1
+        assert pid not in self.inflight, 'Invalid PID encountered'
+
+        correlation_data = json.dumps({
+            'id': self.uuid.hex,
+            'pid': pid,
+        })
 
         value = json.dumps(value)
         logger.info('Sending %s to "%s"', value, setting_topic)
         fut = asyncio.get_running_loop().create_future()
-        self.inflight[response_topic] = fut
+
+        self.inflight[pid] = fut
         self.client.publish(setting_topic, payload=value, qos=0, retain=True,
-                            response_topic=response_topic)
+                            response_topic=response_topic,
+                            correlation_data=correlation_data)
         return await fut
 
 
 def main():
+    """ Main program entry point. """
     parser = argparse.ArgumentParser(
         description='Miniconf command line interface.',
         formatter_class=argparse.RawDescriptionHelpFormatter,
@@ -110,15 +144,13 @@ def main():
 
     async def configure_settings():
         interface = await Miniconf.create(args.prefix, args.broker)
-        failures = 0
-        for kv in args.settings:
-            path, value = kv.split("=", 1)
+        for key_value in args.settings:
+            path, value = key_value.split("=", 1)
             code, response = await interface.command(path, json.loads(value))
-            print(response)
+            print(f'{path}: {response}')
             if code != 0:
-                failures += 1
-
-        return failures
+                return code
+        return 0
 
     sys.exit(loop.run_until_complete(configure_settings()))