Load Testing, Performance Testing, Scalability, Web Development

An Open Source Performance Testing Tool for Scalable Web Applications

December 21, 2023

Locust: An Open Source Performance Testing Tool for Scalable Web Applications

As web applications continue to grow in complexity and scale, ensuring their performance under heavy load becomes crucial. Enter Locust, an open-source performance and load testing tool designed to provide developers with a developer-friendly and scalable solution.

A Developer-Friendly Approach

Locust allows you to write your test scenarios in regular Python code, making it easy to define complex user behavior and perform calculations. Unlike other tools that use proprietary languages or GUI-based interfaces, Locust leverages the flexibility and power of Python, enabling you to use your preferred IDE and version control your tests like any other code.

Here’s an example of a simple Locust test scenario written in Python:

“`python
from locust import HttpUser, task, between

class QuickstartUser(HttpUser):
wait_time = between(1, 2)

def on_start(self):
    self.client.post("/login", json={"username":"foo", "password":"bar"})

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

@task(3)
def view_item(self):
    for item_id in range(10):
        self.client.get(f"/item?id={item_id}", name="/item")

“`

Distributed & Scalable Testing

One of the standout features of Locust is its ability to handle hundreds of thousands of users by distributing the load over multiple machines. Leveraging an event-based architecture, Locust can handle many thousands of concurrent users within a single process. Its low overhead and efficient resource utilization make it an ideal choice for testing highly concurrent workloads.

User-Friendly Web Interface

Locust provides a user-friendly web interface that allows you to monitor the progress of your test in real-time. You can view metrics such as throughput, response times, and errors as they happen. The web interface also allows you to adjust the load dynamically during the test, making it suitable for continuous integration and deployment (CI/CD) testing. Additionally, Locust can be run without the web interface, further enhancing its flexibility and integration capabilities.

Testing Any System or Protocol

While Locust is primarily designed for web applications and services, its flexibility allows it to test almost any system or protocol. You can write a custom client for the system or protocol you want to test, or explore the available clients created by the community.

Hackable and Customizable

Locust’s codebase is intentionally kept small to provide developers with the freedom to adapt it to any situation. You can extend Locust’s functionality by writing custom code, such as sending real-time reporting data to TimescaleDB and visualizing it in Grafana, handling REST API peculiarities, or creating a completely custom load shape or profile.

Getting Started with Locust

To get started with Locust, head over to the documentation and dig into the rich set of resources available. You can find support and answers to your questions on StackOverflow and join the vibrant Locust community on Slack. Locust is an open-source project, and your contributions and feedback are highly valued.

So, if you’re looking for a powerful, scalable, and developer-friendly tool to test the performance of your web applications, give Locust a try. Join the community, contribute to its development, and unleash the full potential of performance testing for your applications.

References

Documentation: docs.locust.io
Support/Questions: StackOverflow
Chat/Discussion: Slack (signup)

Authors

Maintainer: Lars Holmberg
Modern UI: Andrew Baldwin
Original creator: Jonatan Heyman
Massive thanks to all of our contributors

License

Locust is open-source licensed under the MIT license. Please refer to the LICENSE file for more information.

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