locust README

The project's README from github.com/locustio/locust. As one markdown file: README.md.

Locust

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Locust is an open source performance/load testing tool for HTTP and other protocols. Its developer-friendly approach lets you define your tests in regular Python code.

Locust tests can be run from command line or using its web-based UI. Throughput, response times and errors can be viewed in real time and/or exported for later analysis.

You can import regular Python libraries into your tests, and with Locust's pluggable architecture it is infinitely expandable. Unlike when using most other tools, your test design will never be limited by a GUI or domain-specific language.

To get started right away, head over to the documentation.

Features

Write user test scenarios in plain old Python

If you want your users to loop, perform some conditional behaviour or do some calculations, you just use the regular programming constructs provided by Python. Locust runs every user inside its own greenlet (a lightweight process/coroutine). This enables you to write your tests like normal (blocking) Python code instead of having to use callbacks or some other mechanism. Because your scenarios are “just python” you can use your regular IDE, and version control your tests as regular code (as opposed to some other tools that use XML or binary formats)

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 - supports hundreds of thousands of users

Locust makes it easy to run load tests distributed over multiple machines. It is event-based (using gevent), which makes it possible for a single process to handle many thousands concurrent users. While there may be other tools that are capable of doing more requests per second on a given hardware, the low overhead of each Locust user makes it very suitable for testing highly concurrent workloads.

Web-based UI

Locust has a user friendly web interface that shows the progress of your test in real-time. You can even change the load while the test is running. It can also be run without the UI, making it easy to use for CI/CD testing.

Locust UI charts Locust UI stats Locust UI workers Locust UI start test

Can test any system

Even though Locust primarily works with web sites/services, it can be used to test almost any system or protocol. Just write a client for what you want to test, or explore some created by the community.

Hackable

Locust's code base is intentionally kept small and doesn't solve everything out of the box. Instead, we try to make it easy to adapt to any situation you may come across, using regular Python code. There is nothing stopping you from:

VS Code extension

Microsoft has built an excellent VS Code extension that uses Copilot to help you create and run Locust tests. Here's a video to get you started:

Youtube video

Azure Load Testing

Azure offers a managed load-testing service that lets you run and scale Locust tests easily.

Authors

Special thanks

Microsoft contributes to and sponsors the continued maintenance of Locust ❤️

License

Open source licensed under the MIT license (see LICENSE file for details).

locust (locustio/locust)

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28.2K ·GitHub
Locust
What is this?Locust is an open source performance/load testing tool for HTTP and other protocols — you define your tests in regular Python code and run them from the command line or a web-based UI.
So do I click around a GUI or write code to use it?You write test scenarios in regular Python (loops, conditionals, calculations — normal constructs), then run them from the command line or through a web interface. Tests live as code, so your IDE and version control work as usual.
How do I get my first test running?pip install locust, write a user scenario in a Python file, then run the locust command — it serves a web UI where you start and tune the swarm. The full walkthrough is at docs.locust.io.
What's the catch — is there anything it's not great at?Some other tools can push more requests per second on the same hardware — the trade-off is very low overhead per simulated user, ideal for highly concurrent workloads. The codebase is also intentionally small and doesn't solve everything out of the box.
How does it simulate thousands of users at once?Each simulated user runs inside its own greenlet, a lightweight coroutine — so you write scenarios like normal blocking Python code instead of juggling callbacks.
Is there editor or IDE support for writing tests?Yes — Microsoft built a VS Code extension that uses Copilot to help you create and run Locust tests; Microsoft also contributes to and sponsors the project's maintenance.
Can I run my tests on a managed cloud service?Azure Load Testing runs and scales Locust tests for you with no infrastructure to host, can combine results with resource metrics to pinpoint bottlenecks, and integrates with Azure DevOps and GitHub CI pipelines.
What are similar projects?vegeta, k6, oha, wrk, hey, goreplay, ava, workflow
Which topics is it in?load-testing, socket-io, benchmarking, concurrency, http, distributed-systems, testing, devops, performance, framework, tool, docker
Creator
locustio
Size
39.1 MB
Stars
28.2K
Updated
CommitOct 16Release2.46.7Oct 04
Age
15y
Commits · 90 Days