Getting Started with Locust for Performance Testing

Locust is a Python‑based load testing tool that lets you simulate many users to evaluate the performance of web applications or other network services.

1. Install Locust – Use pip: pip install locust.

2. Write a Locust test script – Create a locustfile.py defining user behavior. Example:

from locust import HttpUser, task, between

class WebsiteUser(HttpUser):
    wait_time = between(1, 5)  # random wait between tasks

    @task
    def index(self):
        self.client.get("/")

    @task(3)
    def view_items(self):
        for item_id in range(10):
            self.client.get(f"/item?id={item_id}", name="/item")
            time.sleep(1)  # think time

3. Start Locust – Run locust -f locustfile.py to launch the web UI (default http://localhost:8089).

4. Configure and run the test – In the UI, set total users, spawn rate, and target host URL, then click “Start swarming”.

5. Analyze results – The dashboard shows RPS, average response time, failure rate, etc. Export data with

locust -f locustfile.py --headless -u 100 -r 10 -t 1m --csv=results

for further analysis.

Advanced usage – You can create custom clients for non‑HTTP protocols, run distributed tests for large scale, and use event listeners to implement complex logic.