EventBroadcaster: Log and raise when listener task fails to connect

Author: roekatz

fastapi_websocket_pubsub/event_broadcaster.py

@@ -65,7 +65,7 @@ async def __aenter__(self):
                         "Listening for incoming events from broadcast channel (first listener started)"
                     )
                     # Start task listening on incoming broadcasts
-                    self._event_broadcaster.start_reader_task()
+                    await self._event_broadcaster.start_reader_task()
 
             if self._share:
                 self._event_broadcaster._share_count += 1
@@ -159,6 +159,7 @@ def __init__(
         self._context_manager = None
         self._context_manager_lock = asyncio.Lock()
         self._tasks = set()
+        self.listening_broadcast_channel = None
 
     async def __broadcast_notifications__(self, subscription: Subscription, data):
         """
@@ -221,9 +222,12 @@ async def __aenter__(self):
         return await self._context_manager.__aenter__()
 
     async def __aexit__(self, exc_type, exc, tb):
+        if self.listening_broadcast_channel is not None:
+            await self.listening_broadcast_channel.disconnect()
+            self.listening_broadcast_channel = None
         await self._context_manager.__aexit__(exc_type, exc, tb)
 
-    def start_reader_task(self):
+    async def start_reader_task(self):
         """Spawn a task reading incoming broadcasts and posting them to the intreal notifier
         Raises:
             BroadcasterAlreadyStarted: if called more than once per context
@@ -237,6 +241,20 @@ def start_reader_task(self):
                 "No need for listen task, already started broadcast listen task for this notifier"
             )
             return
+
+        # Init new broadcast channel for reading
+        try:
+            if self.listening_broadcast_channel is None:
+                self.listening_broadcast_channel = self._broadcast_type(
+                    self._broadcast_url
+                )
+                await self.listening_broadcast_channel.connect()
+        except Exception as e:
+            logger.error(
+                f"Failed to connect to broadcast channel for reading incoming events: {e}"
+            )
+            raise e
+
         # Trigger the task
         logger.debug("Spawning broadcast listen task")
         self._subscription_task = asyncio.create_task(self.__read_notifications__())
@@ -249,44 +267,41 @@ async def __read_notifications__(self):
         """
         read incoming broadcasts and posting them to the intreal notifier
         """
-        logger.info("Starting broadcaster listener")
-        # Init new broadcast channel for reading
-        listening_broadcast_channel = self._broadcast_type(self._broadcast_url)
-        async with listening_broadcast_channel:
-            # Subscribe to our channel
-            async with listening_broadcast_channel.subscribe(
-                channel=self._channel
-            ) as subscriber:
-                async for event in subscriber:
-                    try:
-                        notification = BroadcastNotification.parse_raw(event.message)
-                        # Avoid re-publishing our own broadcasts
-                        if notification.notifier_id != self._id:
-                            logger.debug(
-                                "Handling incoming broadcast event: {}".format(
-                                    {
-                                        "topics": notification.topics,
-                                        "src": notification.notifier_id,
-                                    }
-                                )
+        logger.debug("Starting broadcaster listener")
+        # Subscribe to our channel
+        async with self.listening_broadcast_channel.subscribe(
+            channel=self._channel
+        ) as subscriber:
+            async for event in subscriber:
+                try:
+                    notification = BroadcastNotification.parse_raw(event.message)
+                    # Avoid re-publishing our own broadcasts
+                    if notification.notifier_id != self._id:
+                        logger.debug(
+                            "Handling incoming broadcast event: {}".format(
+                                {
+                                    "topics": notification.topics,
+                                    "src": notification.notifier_id,
+                                }
                             )
-                            # Notify subscribers of message received from broadcast
-                            task = asyncio.create_task(
-                                self._notifier.notify(
-                                    notification.topics,
-                                    notification.data,
-                                    notifier_id=self._id,
-                                )
+                        )
+                        # Notify subscribers of message received from broadcast
+                        task = asyncio.create_task(
+                            self._notifier.notify(
+                                notification.topics,
+                                notification.data,
+                                notifier_id=self._id,
                             )
+                        )
 
-                            self._tasks.add(task)
+                        self._tasks.add(task)
 
-                            def cleanup(task):
-                                self._tasks.remove(task)
+                        def cleanup(task):
+                            self._tasks.remove(task)
 
-                            task.add_done_callback(cleanup)
-                    except:
-                        logger.exception("Failed handling incoming broadcast")
-                logger.info(
-                    "No more events to read from subscriber (underlying connection closed)"
-                )
+                        task.add_done_callback(cleanup)
+                except:
+                    logger.exception("Failed handling incoming broadcast")
+            logger.info(
+                "No more events to read from subscriber (underlying connection closed)"
+            )