Django Daphne – Database connections max out + "took too long to shut down"

Question

I'm implementing a messaging system, but experiencing the following two errors on the dev server:

1. "Application instance <...> took too long to shut down and was killed."
2. The database connections get increased on every new EventSource that is created, despite it being closed on the frontend.

Here is my code:

Backend:

@transaction.non_atomic_requests
async def stream_chat_messages(request: HttpRequest) -> StreamingHttpResponse:

    async def event_stream():
        SLEEP_INTERVAL = 0.3

        """
        We use this function to send a continuous stream of data
        to the connected clients.
        """
        async for message in get_existing_messages():
            yield message

        last_id = await get_last_message_id()

        # Continuously check for new messages
        while True:
            new_messages = _get_messages().filter(id__gt=last_id)
            async for message in new_messages:
                yield f"data: {json.dumps(message)}\n\n"
                last_id = message["id"]
            await asyncio.sleep(SLEEP_INTERVAL)

    return StreamingHttpResponse(event_stream(), content_type="text/event-stream")

Frontend (React):

  const [currentChatroom, setCurrentChatroom] = useState<ChatroomProps | null>(
    null,
  );
  useEffect(() => {
    setMessages([]);

    if (!currentChatroom) return;

    let sse = new EventSource(
      `.../stream-chat-messages/?chatroom=${currentChatroom.id}`,
    );
    sse.onmessage = (event) => {
      // ...
    };
    sse.onerror = () => {
      sse.close();
    };
    
    return () => {
      sse.close();
    };
  }, [currentChatroom?.id]);

What am I doing wrong here? Every time the page is loaded, a new database connection is created, but it keeps persisting.

Thanks!