Demo on Impact of Blocking Operation to Async Web Application

app.py

from asyncio import sleep as asleep
from time import sleep

from fastapi import FastAPI

app = FastAPI()


@app.get("/good")
async def good():
    await asleep(2)
    return {"message": "Good"}


@app.get("/bad")
async def bad():
    sleep(2)
    return {"message": "Bad"}

Makefile

WORKERS?=1
NUM_REQ?=1

run:
	uvicorn --workers $(WORKERS) app:app

request-bad:
	python request.py http://127.0.0.1:8000/bad -n $(NUM_REQ)

request-good:
	python request.py http://127.0.0.1:8000/good -n $(NUM_REQ)

request.py

import argparse
from concurrent.futures import ThreadPoolExecutor as Pool
from time import time

import requests


def fetch(url):
    start = time()
    response = requests.get(url)
    duration = time() - start
    print(duration)
    return response.json()


def main(url, n: int = 4):
    with Pool(n) as pool:
        _ = pool.map(fetch, [url] * n)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("url", type=str, help="The URL to fetch")
    parser.add_argument(
        "-n", type=int, default=4, help="The number of requests to make"
    )
    kwargs = vars(parser.parse_args())
    main(**kwargs)

requirements.txt

fastapi==0.111.0
requests==2.31.0