Celery, uvicorn and FastAPI

Question

I have a FastAPI api code that is executed using uvicorn. Now I want to add a queu system, and I think Celery and Flower can be great tools for me since my api has some endpoints that uses a lot CPU and take some seconds in answering. However, I have a couple of questions about the addition of Celery:

1. Does Celery substitute Uvicorn? Do I need it any more? I cannot see any example on the website where they consider uvicorn too, and when you execute the Celery seems to do not need it...
2. I have read a lot about using Celery for creating a queu for FastAPI. However, you can manage a queue in FastAPI without using Celery. What's better? and why?

Answer 1

Does Celery substitute Uvicorn?

No. Celery is not a replacement for Uvicorn. Uvicorn is meant to run your FastAPI application, Celery will not do that for you.

I have read a lot about using Celery for creating a queu for FastAPI. However, you can manage a queue in FastAPI without using Celery. What's better? and why?

I guess you mean the BackgroundTasks here, but that is not a replacement for Celery. FastAPI BackgroundTasks are meant to execute simple tasks (and not CPU bound related tasks).

Answering the question, ideally, you'd have to start both services: Uvicorn, and Celery. You can see an example on how to do it here.

Not that it matters much here, but I'm one of the Uvicorn maintainers.