update

backend/ws.py

@@ -12,9 +12,21 @@ class Hub:
     def __init__(self):
         self._clients: set = set()
         self._loop: asyncio.AbstractEventLoop | None = None
+        self._queue: asyncio.Queue | None = None
 
     def bind_loop(self, loop: asyncio.AbstractEventLoop) -> None:
         self._loop = loop
+        self._queue = asyncio.Queue()
+        # EIN Sender-Task serialisiert die Broadcasts — ein Task-pro-push konnte
+        # sich bei Backpressure überholen (out-of-order-Deltas, konkurrierende
+        # send_text auf demselben Socket).
+        loop.create_task(self._sende_schleife())
+
+    async def _sende_schleife(self) -> None:
+        assert self._queue is not None
+        while True:
+            msg = await self._queue.get()
+            await self._send_all(msg)
 
     async def connect(self, websocket) -> None:
         await websocket.accept()
@@ -24,11 +36,12 @@ class Hub:
         self._clients.discard(websocket)
 
     def push(self, tabelle: str, row: dict) -> None:
-        """Thread-sicher (DB-Schicht ruft synchron): auf den Loop dispatchen."""
-        if not self._clients or self._loop is None:
+        """Thread-sicher (DB-Schicht ruft synchron): in die Queue legen, der
+        Sender-Task verschickt der Reihe nach."""
+        if not self._clients or self._loop is None or self._queue is None:
             return
         msg = json.dumps({"tabelle": tabelle, "row": row}, ensure_ascii=False, default=str)
-        self._loop.call_soon_threadsafe(lambda: asyncio.ensure_future(self._send_all(msg)))
+        self._loop.call_soon_threadsafe(self._queue.put_nowait, msg)
 
     async def _send_all(self, msg: str) -> None:
         for ws in list(self._clients):