anyio.BusyResourceError: Another task is already writing to this resource

[ZzZombo]

  File "~~~~.py", line 80, in resolve_url
    await self.ws.send_json(data)
  File "~~~~\Lib\site-packages\httpx_ws\_api.py", line 701, in send_json
    await self.send_text(serialized_data)
  File "~~~~\Lib\site-packages\httpx_ws\_api.py", line 659, in send_text
    await self.send(event)
  File "~~~~\Lib\site-packages\httpx_ws\_api.py", line 638, in send
    await self.stream.write(data)
  File "~~~~\Lib\site-packages\httpcore\backends\asyncio.py", line 51, in write
    await self._stream.send(item=buffer)
  File "~~~~\Lib\site-packages\anyio\_backends\_asyncio.py", line 1291, in send
    with self._send_guard:
  File "~~~~\Lib\site-packages\anyio\_core\_synchronization.py", line 584, in __enter__
    raise BusyResourceError(self.action)
anyio.BusyResourceError: Another task is already writing to this resource

I can't quite trace the conditions for the above error, because it only happens occasionally.

[frankie567]

Quite hard to tell what's going wrong from this 🤔 Do you try to send several messages concurrently in the same WebSocket?

[ZzZombo]

From the output it doesn't seem so. It may appear once in a thousand calls within several hours or several times within a minute. All captured instances had at least ~10ms between calls though. Ironically my admittedly quite crude attempts at fixing it seemed only to severely increase the rate of the error occurring. But question: isn't WS supposed to handle simultaneous messages just fine?

[Emsu]

@frankie567 I get this too with audiostreams through websockets in the latest version still.

It looks like it's the background ping writing to the socket at the same time in my case. Sometimes the background ping throws the error and sometime's it's the audio stream data depending on who wrote first and which coroutine got the error.

Is there some way we can make the background ping not cause an error in the userland code?