Slow requests due to possibly incorrect break.

[blubard]

With FastAPI, under certain circumstances I was noticing some calls were very slow.

It turned out that in starlette version 0.20.1, a break was added into the body_stream method (BaseHTTPMiddleware).

This break omits the final __anext__ of MemoryObjectReceiveStream (resp. UnreliableObjectReceiveStream) and hence will never raise the necessary StopAsyncIteration to properly exit the async for loop.

I am not sure why this results in a "slow" response and not in something more fatal, I guess my knowledge of async python is too limited... (is there something timing out?). Also I am not sure why this occurs not for all my calls; after I raise in fastapi, the follow up REST request is fast again.

A "fix" was to close the recv_stream instead of using the break.

Is this a real issue or was this break intended to behave as it does? Is it likely that the issue is due to invalid usage from my side?

[Kludex]

Yeah, this is correct. I didn't see it soon enough.

That logic was removed. Thanks 👍