Method websocket_handler

dash/backends/_fastapi.py:706–835

(websocket: WebSocket)

            return None

        async def websocket_handler(websocket: WebSocket):
            # Validate Origin header to prevent Cross-Site WebSocket Hijacking
            origin = websocket.headers.get("origin")
            host = websocket.headers.get("host")
            error = validate_origin(origin, host)
            if error:
                await websocket.close(code=4003, reason=error)
                return

            # Call websocket_connect hooks (before accept)
            # pylint: disable=protected-access
            rejection = await self._run_ws_hooks(
                dash_app._hooks.get_hooks("websocket_connect"),
                websocket,
                default_reason="Connection rejected",
            )
            if rejection:
                await websocket.close(code=rejection[0], reason=rejection[1])
                return

            await websocket.accept()

            # Create janus queue for outbound messages (main loop context)
            outbound_queue: janus.Queue[str] = janus.Queue()
            # Track pending get_props requests with standard queue.Queue for responses
            pending_get_props: Dict[str, queue.Queue] = {}
            # Shutdown event to signal connection closure to worker threads
            shutdown_event = threading.Event()
            # Get thread pool executor
            executor = self.get_callback_executor()
            # Track pending callback futures
            pending_callbacks: Dict[str, concurrent.futures.Future] = {}

            # Start sender task to drain outbound queue (sends pre-serialized text)
            # pylint: disable=protected-access
            batch_delay = getattr(dash_app, "_websocket_batch_delay", 0.005)
            sender_task = asyncio.create_task(
                run_ws_sender(websocket.send_text, outbound_queue, batch_delay)
            )

            try:
                while True:
                    message = await websocket.receive_json()

                    # Call websocket_message hooks
                    rejection = await self._run_ws_hooks(
                        dash_app._hooks.get_hooks("websocket_message"),
                        websocket,
                        message,
                        default_reason="Message rejected",
                    )
                    if rejection:
                        await websocket.close(code=rejection[0], reason=rejection[1])
                        return

                    msg_type = message.get("type")

                    if msg_type == "callback_request":