Load testing a server

2022 Jun 12 See all posts

Load testing a server

What is load testing? ⁉️

Quoting wikipedia:

Load testing generally refers to the practice of modeling the expected usage of a software program by simulating multiple users accessing the program concurrently.

Let's get started then! 🏁

Requirements

We are gonna load test our server using Locust, a simple and straight forward python library.

Install locust by running:

pip3 install locust

Test the installation:

locust -V

Load testing

Create a python file locustfile.py and add the following code in it:

from locust import HttpUser, task

class  HelloWorldUser(HttpUser):
@task
def  hello_world(self):
    self.client.get("/") #URL that we will request

In the same folder, start testing by running:

locust

You should see something similar to:

Terminal

Now, you can access http://localhost:8089

You will now see Locust UI

Localhost UI

Configure according your preferred settings and off you go! 🏎️

Testing

You will be able to see the stats of your ongoing test:

Testing Preview

One you stop testing, you can analise your results using the different views that locust offers:

Charts

or you can simply preview the terminal view

Terminal view

Welldone! You have load tested a server using locust, congrats! 🎉

One step further, a more realistic test

Make a more realistic and suitable test by modifying the locustfile to your needs

import time
from json import JSONDecodeError
from locust import HttpUser, task, between

class QuickstartUser(HttpUser):

# Waiting time after between each task ran by users
wait_time = between(1, 5)

@task
def hello_world(self):
    self.client.get("/hello")
    self.client.get("/world")

# "3" refers to the task's weight (it's 3 times more likely to be ran)
@task(3)
def view_items(self):
    for item_id in range(10):
        # group requests with different parameters together
        self.client.get(f"/item?id={item_id}", name="/item")
        time.sleep(1)

# call an API and validate its response
with self.client.post("/", json={"foo": 42, "bar": 69}, catch_response=True) as response:
try:
    if response.json()["greeting"] != "hello":
        response.failure("Did not get expected value in greeting")
except JSONDecodeError:
    response.failure("Response could not be decoded as JSON")
except KeyError:
    response.failure("Response did not contain expected key 'greeting'")

With locust you can test your server fairly quickly with its simple setup.

Its configuration is also well docummented, take a look at their official site: Locust documentation

Happy load testing! 🛩️