FastAPI sync vs async performance testing

Question

I wrote simple fastapi server in which I want to do performance testing. Which means that I would like to test async vs. sync endpoint, but I got always the same results. Which concept I don't understand or what I am doing wrong?

from fastapi import FastAPI
import time
import asyncio
app = FastAPI()


@app.get("/hello")
def say_hello():
    time.sleep(5)


@app.get("/hello-async")
async def say_hello():
    await asyncio.sleep(5)

I run server like this: gunicorn main:app --workers=4 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000

And do performance testing:

ab -n 80 -c 8 http://localhost:8000/hello-async
ab -n 80 -c 8 http://localhost:8000/hello

And got this kind of results:

This is ApacheBench, Version 2.3 <$Revision: 1879490 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient).....done


Server Software:        uvicorn
Server Hostname:        localhost
Server Port:            8000

Document Path:          /hello-async
Document Length:        4 bytes

Concurrency Level:      8
Time taken for tests:   55.016 seconds
Complete requests:      80
Failed requests:        0
Total transferred:      10240 bytes
HTML transferred:       320 bytes
Requests per second:    1.45 [#/sec] (mean)
Time per request:       5501.634 [ms] (mean)
Time per request:       687.704 [ms] (mean, across all concurrent requests)
Transfer rate:          0.18 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       1
Processing:  5000 5001   0.6   5001    5003
Waiting:     5000 5001   0.6   5001    5003
Total:       5000 5001   0.6   5001    5003

Percentage of the requests served within a certain time (ms)
  50%   5001
  66%   5002
  75%   5002
  80%   5002
  90%   5002
  95%   5002
  98%   5003
  99%   5003
 100%   5003 (longest request)

I wanted to simulate I/O operation, if I call API or database I want to se how much faster is async approach. What happened now I got the same time taken for tests.

If I would do CPU intensive operation I would understand that I will got the same result. What I am doing wrong?

Also in syncing approach the web server is limited to number threads which are spawned, but then what is theoretical limit of async approach? Also how can I test limits number of spawned threads in syncing approach and in async approach what is the limit of event loop.

FastAPI sync vs async performance testing

0 Answers