Locust vs Wrk: What are the differences?

Introduction

In this article, we will explore the key differences between Locust and Wrk. Locust and Wrk are both widely used tools for load testing and performance evaluation of web applications. However, they have some distinct features that set them apart. Let's dive into the specifics below.

1. Architecture: Locust is a distributed load testing tool that uses a master-slave setup, where the master controls the test execution and the slaves generate user loads. On the other hand, Wrk is a command-line tool that runs on a single machine and generates a high number of connections to stress test the server.

2. Scripting Language: Locust provides a user-friendly scripting interface that allows testers to write load testing scenarios using Python code. It offers flexibility and customizability to simulate realistic user behavior. In contrast, Wrk does not provide a scripting language and relies on command-line options for specifying the load testing parameters.

3. Scalability: Locust is designed to scale horizontally by adding more slave nodes to distribute the load across multiple machines. This allows for high concurrency and the ability to simulate millions of concurrent users. Wrk, being a single-threaded tool, is limited to the capabilities of a single machine and cannot scale horizontally.

4. Metrics and Reporting: Locust provides a detailed web-based UI that displays real-time statistics and graphs during the load test. It offers various metrics such as response times, requests per second, and failure rates. Additionally, Locust allows exporting test results in formats like CSV and JSON for further analysis. In contrast, Wrk lacks a built-in reporting capability, and users need to manually process the output using external tools.

5. Request Injection: Locust allows dynamic request generation and injection, providing better test case variability. Testers can parametrize requests and inject data from external sources. Wrk, being a simple load generator, does not support dynamic request injection and requires test cases to be predefined before the test execution.

6. Concurrency Model: Locust uses an event-driven, cooperative multitasking model known as gevent. This allows the simulation of thousands of concurrent users with a relatively low number of threads. Wrk, on the other hand, follows a more traditional thread-per-connection model, which can create a higher overhead when dealing with a large number of connections.

In summary, Locust offers a distributed architecture, a flexible scripting language, scalability across multiple machines, comprehensive reporting capabilities, dynamic request injection, and an efficient concurrency model. Wrk, on the other hand, is a simpler tool with a single-threaded design, limited scalability, and lacks advanced reporting features.