[Python知识库][pypi test drive] Locust (performance testing tool)

Locust

Locust claims to be:

an easy to use, scriptable and scalable performance testing tool.

and to be more specific:

You define the behaviour of your users in regular Python code, instead of using a clunky UI or domain specific language

and the features include:

• Write user test scenarios in plain old Python
• Distributed & Scalable - supports hundreds of thousands of users
• Web-based UI
• Can test any system
• Hackable

Fact check

Test drive environment

Package dependencies (after pip install)

python -m pip install locust==1.6.0
python -m pip list

gives:

Package       Version
------------- ---------
certifi          2021.5.30
cffi             1.14.6
chardet          4.0.0
click            8.0.1
colorama         0.4.4
ConfigArgParse   1.5.1
Flask            1.1.2
Flask-BasicAuth  0.2.0
Flask-Cors       3.0.10
gevent           21.1.2
geventhttpclient 1.4.4
greenlet         1.1.0
idna             2.10
itsdangerous     2.0.1
Jinja2           3.0.1
locust           1.6.0
MarkupSafe       2.0.1
msgpack          1.0.2
pip              21.1.3
psutil           5.8.0
pycparser        2.20
pywin32          301
pyzmq            22.1.0
requests         2.25.1
setuptools       57.1.0
six              1.16.0
urllib3          1.26.6
Werkzeug         2.0.1
wheel            0.36.2
zope.event       4.5.0
zope.interface   5.4.0

Test drive

Setup target web application (flask):

# app.py

from flask import Flask


app = Flask(__name__)


@app.route("/")
def home() -> str:
    return "<p>Hellow world!</p>"


@app.route("/<int:number>")
def lucky_number(number: int) -> str:
    return f"<p>Your lucky number is {number}!</p>"

and:

python -m flask run

Then the terminal shows:

 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Setup test runner:

# runner.py

import random
from typing import Callable

from locust import HttpUser, between, task


class FlaskAppUser(HttpUser):
    wait_time: Callable = between(min_wait=1, max_wait=3)

    # Overwrite this to customize initial behavior
    def on_start(self) -> None:
        return super().on_start()

    @task(weight=3)
    def go_home(self) -> None:
        self.client.get("/")

    @task(weight=1)
    def go_lucky_number(self) -> None:
        for _ in range(10):
            self.client.get(f"/{random.randint(100, 999)}")

and:

python -m locust -f runner.py

Then the terminal shows:

[2021-07-12 ******] DESKTOP-******/INFO/locust.main: Starting web interface at http://0.0.0.0:8089 (accepting connections from all network interfaces)
[2021-07-12 ******] DESKTOP-******/INFO/locust.main: Starting Locust 1.6.0

Run the test:

Go to http://localhost:8089/ in the browser and the locust page is shown, fill in the desired parameter as well as the host of the target flask app:

Click Start swarming button in the page and the test starts to run, and the statistics are populated in real time:

The Charts tab shows graphs:

At any time, click the STOP botton on top-right corner to stop the current run.
The terminal in which the runner runs shows like:

[2021-07-12 ******] DESKTOP-******/INFO/locust.runners: Spawning 10 users at the rate 10 users/s (0 users already running)...
[2021-07-12 ******] DESKTOP-******/INFO/locust.runners: All users spawned: FlaskAppUser: 10 (10 total running)
[2021-07-12 ******] DESKTOP-******/INFO/locust.runners: Stopping 10 users
[2021-07-12 ******] DESKTOP-******/INFO/locust.runners: 10 Users have been stopped, 0 still running