Future from granian being wrongly treated

[hermeschen1116]

@Kludex Hello, I’ve encountered some issues using sse-starlette with Granian and have reached out to the Granian maintainer for help. You can find the details of the issue on GitHub at emmett-framework/granian#698. He suspects that the future might be incorrectly handled in either FastAPI or Starlette. While this only results in a warning, would you be able to assist me with this?

[Kludex]

Do you have an MRE?

[hermeschen1116]

Here is how I implement the API.

@router.get(
	"/capture/stream",
	status_code=status.HTTP_200_OK,
	responses={
		"200": {"description": "回傳串流擷取結果"},
		"404": {"description": "不存在的串流"},
		"422": {"description": "錯誤的 UUID 格式"},
		"503": {"description": "擷取串流時出現錯誤"},
	},
	description="擷取指定串流畫面",
)
async def stream_frame(
	request: Request,
	stream_id: typing.Annotated[
		uuid.UUID, Query(description="串流來源 ID", example="07c9f116-feb1-5e24-97fc-f400c03e935a")
	],
):
	"""擷取串流畫面"""

	if not request.app.state.streams:
		await LOGGER.awarning(msg := "🏞️ 無任何串流")
		raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=msg)

	if request.app.state.streams.get(stream_id) is None:
		await LOGGER.awarning(msg := f"🏞️ 串流（stream_id：{stream_id}）不存在")
		raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=msg)

	async def frame_streamer():
		frame_queue: CyclicPriorityQueue = await request.app.state.frame_buffer.register()
		try:
			while not (await request.is_disconnected()):
				_, frames = await frame_queue.get()
				if (image := frames[stream_id].frame) is None:
					continue
				yield (
					b"--frame\r\nContent-Type: image/webp\r\n\r\n"
					+ image
					+ b"\r\nX-TIMESTAMP: "
					+ frames[stream_id].timestamp.isoformat().encode("utf-8")
					+ b"\r\nX-STREAM-ID: "
					+ str(frames[stream_id].stream_id).encode("utf-8")
					+ b"\r\n"
				)
				await LOGGER.ainfo(f"🏞️ 擷取串流畫面（{frames[stream_id].timestamp}）")
		except asyncio.CancelledError as e:
			await LOGGER.awarning(f"⚠️ Client（{request.client}）中斷連接")
			raise e
		finally:
			await request.app.state.frame_buffer.unregister(frame_queue)

	return StreamingResponse(frame_streamer(), media_type="multipart/x-mixed-replace; boundary=frame")