How to terminate a Uvicorn + FastAPI application cleanly with workers >= 2 when testing with pytest

Question

I have an application written with Uvicorn + FastAPI. I am testing the response time using PyTest.

Referring to How to start a Uvicorn + FastAPI in background when testing with PyTest, I wrote the test. However, I found the application process alive after completing the test when workers >= 2.

I want to terminate the application process cleanly at the end of the test.

Do you have any idea?

The details are as follows.

Environment

Windows 10
Bash 4.4.23 (https://cmder.net/)
python 3.7.5

Libraries

fastapi == 0.68.0
uvicorn == 0.14.0
requests == 2.26.0
pytest == 6.2.4

Sample Codes

Application: main.py

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def hello_world():
    return "hello world"

Test: test_main.py

from multiprocessing import Process
import pytest
import requests
import time
import uvicorn

HOST = "127.0.0.1"
PORT = 8765
WORKERS = 1


def run_server(host: str, port: int, workers: int, wait: int = 15) -> Process:
    proc = Process(
        target=uvicorn.run,
        args=("main:app",),
        kwargs={
            "host": host,
            "port": port,
            "workers": workers,
        },
    )
    proc.start()
    time.sleep(wait)
    assert proc.is_alive()
    return proc


def shutdown_server(proc: Process):
    proc.terminate()
    for _ in range(5):
        if proc.is_alive():
            time.sleep(5)
        else:
            return
    else:
        raise Exception("Process still alive")


def check_response(host: str, port: int):
    assert requests.get(f"http://{host}:{port}").text == '"hello world"'


def check_response_time(host: str, port: int, tol: float = 1e-2):
    s = time.time()
    requests.get(f"http://{host}:{port}")
    e = time.time()
    assert e-s < tol


@pytest.fixture(scope="session")
def server():
    proc = run_server(HOST, PORT, WORKERS)
    try:
        yield
    finally:
        shutdown_server(proc)


def test_main(server):
    check_response(HOST, PORT)
    check_response_time(HOST, PORT)
    check_response(HOST, PORT)
    check_response_time(HOST, PORT)

Execution Result

$ curl http://localhost:8765
curl: (7) Failed to connect to localhost port 8765: Connection refused
$ pytest test_main.py
=============== test session starts =============== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: .\
collected 1 item

test_main.py .                                                                                                                                                                                                                         [100%]

=============== 1 passed in 20.23s ===============
$ curl http://localhost:8765
curl: (7) Failed to connect to localhost port 8765: Connection refused
$ sed -i -e "s/WORKERS = 1/WORKERS = 3/g" test_main.py
$ curl http://localhost:8765
curl: (7) Failed to connect to localhost port 8765: Connection refused
$ pytest test_main.py
=============== test session starts =============== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: .\
collected 1 item

test_main.py .                                                                                                                                                                                                                         [100%]

=============== 1 passed in 20.21s ===============
$ curl http://localhost:8765
"hello world"

$ # Why is localhost:8765 still alive?

This is a related version of https://stackoverflow.com/q/61577643/4165272 issue. — polka, Feb 04 '22 at 01:14
I use **sys.exit(4)**. Here are the details: https://stackoverflow.com/a/74117959/1689733 — Alex Protyagov, Oct 18 '22 at 22:11
I use **sys.exit(4)** [Here are more details](https://stackoverflow.com/a/74117959/1689733) — Alex Protyagov, Oct 18 '22 at 22:13

score 4 · Accepted Answer · answered Aug 02 '21 at 12:49

I have found a solution myself.

Thanks > https://stackoverflow.com/a/27034438/16567832

Solution

After install psutil by pip install psutil, update test_main.py

from multiprocessing import Process
import psutil
import pytest
import requests
import time
import uvicorn

HOST = "127.0.0.1"
PORT = 8765
WORKERS = 3


def run_server(host: str, port: int, workers: int, wait: int = 15) -> Process:
    proc = Process(
        target=uvicorn.run,
        args=("main:app",),
        kwargs={
            "host": host,
            "port": port,
            "workers": workers,
        },
    )
    proc.start()
    time.sleep(wait)
    assert proc.is_alive()
    return proc


def shutdown_server(proc: Process):

    ##### SOLUTION #####
    pid = proc.pid
    parent = psutil.Process(pid)
    for child in parent.children(recursive=True):
        child.kill()
    ##### SOLUTION END ####

    proc.terminate()
    for _ in range(5):
        if proc.is_alive():
            time.sleep(5)
        else:
            return
    else:
        raise Exception("Process still alive")


def check_response(host: str, port: int):
    assert requests.get(f"http://{host}:{port}").text == '"hello world"'


def check_response_time(host: str, port: int, tol: float = 1e-2):
    s = time.time()
    requests.get(f"http://{host}:{port}")
    e = time.time()
    assert e-s < tol


@pytest.fixture(scope="session")
def server():
    proc = run_server(HOST, PORT, WORKERS)
    try:
        yield
    finally:
        shutdown_server(proc)


def test_main(server):
    check_response(HOST, PORT)
    check_response_time(HOST, PORT)
    check_response(HOST, PORT)
    check_response_time(HOST, PORT)

Execution Result

$ curl http://localhost:8765
curl: (7) Failed to connect to localhost port 8765: Connection refused
$ pytest test_main.py
================== test session starts ================== platform win32 -- Python 3.7.5, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: .\
collected 1 item

test_main.py .                                                                                                                                                                                                                         [100%]

================== 1 passed in 20.24s ==================
$ curl http://localhost:8765
curl: (7) Failed to connect to localhost port 8765: Connection refused

@WolfgangFahl thanks comment. May I ask you two questions? 1. in which environment did you try the solution? 2. where was the error raised? In my environment, which is written above, my solution still works. — hmasdev, Sep 29 '22 at 13:12

score 1 · Answer 2 · answered Dec 10 '22 at 23:41

1

Follow up of @hmasdev answer

import os
import fastapi
import uvicorn
import psutil

    @app.get("/quit")
    def iquit():
        parent_pid = os.getpid()
        parent = psutil.Process(parent_pid)
        for child in parent.children(recursive=True):  # or parent.children() for recursive=False
            child.kill()
        parent.kill()
    
    
    
    
    if __name__ == '__main__':
        uvicorn.run(app, port=36113, host='127.0.0.1')

answered Dec 10 '22 at 23:41

nether

11
1

1

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Dec 14 '22 at 16:10

How to terminate a Uvicorn + FastAPI application cleanly with workers >= 2 when testing with pytest

Environment

Libraries

Sample Codes

Execution Result

2 Answers2

Solution

Execution Result

Linked