Async background task block main event loop

[benjamin-callonnec]

Hello,

I have my uvicorn server running my FastAPI application.

I have an endpoint which has an asynchronous background task. I observed that running the background task in the main event loop of uvicorn cause the event loop to be blocked while waiting for the background task to finish.

One solution i implemented is to consistently run the background task in a dedicated thread.

https://github.com/encode/starlette/blob/6ee94f2cac955eeae68d2898a8dec8cf17b48736/starlette/background.py#L27

Linked PR: #2974