connexion: Slowdown of cold start in connexion 3.0

Description

When switching to connexion 3.0 we noticed a considerable slowdown at startup. Startup with connexion 3.x: 700ms-1s Startup with connexion 2.x: 1ms-10ms

Expected behaviour

No slowdown at startup compared to connexion 2.x

Actual behaviour

Slowdown at startup.

Steps to reproduce

Have a medium sized OpenApi specification in yaml format (700 lines)

Have a simple app created with a factory method:

# openapi_server/factory.py

from connexion import App


def create_app() -> App:
    connexion_app = App(__name__, specification_dir="./openapi/")
    connexion_app.add_api("openapi.yaml")
    return connexion_app

Use pytest and have a simple dummy unit test: For connexion 3.x:

# tests/test_dummy.py

import pytest
from openapi_server.factory import create_app

@pytest.fixture()
def app():
  return create_app().test_client()

@pytest.mark.parametrize("arg", range(10))
def test_startup(app, arg):
  app.get("/")

For connexion 2.x:

# tests/test_dummy.py

import pytest
import webtest

from openapi_server.factory import create_app


@pytest.fixture()
def app():
    return webtest.TestApp(create_app())


@pytest.mark.parametrize("arg", range(10))
def test_startup(app, arg):
  app.get("/")

Timings:
- connexion 3.x: pytest tests/test_dummy.py 8,97s user 0,11s system 98% cpu 9,188 total
- connexion 2.x: pytest tests/test_dummy.py 2,36s user 0,10s system 85% cpu 2,888 total

Additional info:

Output of the commands:

python --version Python 3.9.18
pip show connexion | grep "^Version\:" Version: 3.0.1

What I tried:

Use AsyncApp (no speedup)
Use different backends for starlette (no speedup)
Use a different python version (some speedup)

Looking at the profiler it seems like the yaml parsing now takes more time?

About this issue

Original URL
State: closed
Created 8 months ago
Comments: 15 (3 by maintainers)

Commits related to this issue

Only instantiate specification once (#1819) Fixes #1801 I had to make quite a few additional changes to satisfy mypy. — committed to spec-first/connexion by RobbeSneyders 7 months ago

Most upvoted comments

Here is an output from the profiler for the same file with tests.

Python 3.10.7 Connexion[flask, uvicorn]==3.0.1 Flask==3.0.0 Screenshot 2023-11-17 at 14 59 37 Screenshot 2023-11-17 at 14 55 01

Python 3.10.7 Connexion==2.14.1 Flask==2.2.5 Screenshot 2023-11-17 at 15 00 37 Screenshot 2023-11-17 at 14 57 31

vladislavkoz on Nov 17, 2023

I also, faced performance issues after the upgrade. Will share some profiling results tomorrow. But what I can see is that my laptop is getting hot with Connexion 3 when I run tests. Tests execution time increased dramatically.

vladislavkoz on Nov 16, 2023

Thanks for the reports everyone, I just submitted a fix. Will release it as a 3.0.3 once it’s merged.

RobbeSneyders on Nov 24, 2023

I have same issue

yevheniimykytiuk on Nov 20, 2023

@RobbeSneyders thank you very much for looking into this, I will try to investigate myself in the meantime 😃

Regarding response time I also didn’t notice any slowdown.

ThomasSchwengler on Nov 14, 2023

I’m indeed able to reproduce a longer startup time in Connexion 3 compared to Connexion 2 using the following script. You can add it to the restyresolver example and install the connexion version you want to test.

import time
from multiprocessing import Process

import requests
from connexion import App
from connexion.resolver import RestyResolver


def start_app():
    app = App(__name__, specification_dir="spec")
    app.add_api(
        "openapi.yaml",
        arguments={"title": "RestyResolver Example"},
        resolver=RestyResolver("api"),
    )
    app.run(port=8080)


def wait_for_app():
    while True:
        try:
            r = requests.get("http://localhost:8080/openapi/pets")
        except Exception:
            pass
        else:
            if r.status_code == 200:
                break


if __name__ == '__main__':
    p = Process(target=start_app)
    start = time.time()
    p.start()
    wait_for_app()
    print(time.time() - start)
    p.kill()

Parsing the specification and passing it to the application has a bigger impact on Connexion 3 than Connexion 2, but can’t completely explain the slowdown. I’ll have a deeper look when I find the time. I can’t really make sense of the v3 pstat file, since almost all time is spent on thread.lock and there’s a lot of pytest stuff in there.

FYI, we did test the response time of Connexion 3 vs Connexion 2 before the release and didn’t notice any meaningful difference between the two.

RobbeSneyders on Nov 14, 2023