Limit FastApi to process only 1 Request at a time.

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn’t find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google “How to X in FastAPI” and didn’t find any information.
• I already read and followed all the tutorial in the docs and didn’t find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.

Commit to Help

• I commit to help with one of those options 👆

Example Code

#main.py
from fastapi import FastAPI
app = FastAPI()

@app.post('/limit')
async def func():
    # Doing some work that may take about 10 - 30 minutes
    return result

Description

I want to limit the requests at this endpoint. As this endpoint will take some time to finish, so once a request comes and it starts being processed, any other request that is made before the finishing of first request gets discarded(Or can get 429 response).

In short I want to add a Limit of 1 REQUEST AT A TIME.

I’ve seen slow-api, fastapi-limiter, and other limiters. But all I got from them was to limit rate according to some time like (10 requests/sec) or similar.

Hope i can get any workaround on this!!

Thanks…

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.73.0

Python Version

Python 3.9.10

Additional Context

https://nordicapis.com/everything-you-need-to-know-about-api-rate-limiting/

This bottleneck seems to do the trick, but I don’t have a clue of implementing this in fastapi.

[tiangolo]

Thanks for the help here everyone! 👏 🙇

If that solves the original problem, then you can close this issue @arjit1804 ✔️

For others with other problems, it’s probably better to create a new issue, following the template, creating a minimal, self-contained example that I can copy paste and replicate the problem, etc.

[tr-gis]

did you try locking the threads?. Seems to work . I tried something like this:

#main.py
from fastapi import FastAPI
import threading

lock = threading.Lock()

app = FastAPI()

@app.post('/limit')
def func():
    lock.acquire()
    # Doing some work that may take about 10 - 30 minutes
    lock.release()
    return result

Note that I changed function def from async to normal def.