wrk

wrk is a high-performance HTTP benchmarking tool designed to generate significant load on a web server. It is open-source, lightweight, and widely used to assess throughput and latency under high concurrency. Written in C, wrk uses an asynchronous, event-driven model to drive many concurrent connections with minimal overhead. It runs on Unix-like systems and can benchmark both HTTP and HTTPS endpoints.

Key features include multi-threaded execution with multiple connections, Lua scripting for customizing requests, and the ability to specify the number of threads, connections, and test duration from the command line. The Lua scripting support enables per-request customization, such as setting headers or generating request bodies, to simulate more complex workloads. During a test, wrk reports metrics such as requests per second, latency statistics (including mean and percentiles), and data transfer rate.

Usage typically involves invoking wrk with a configuration of threads, connections, and duration, followed by the target URL, for example: wrk -t12 -c400 -d30s http://example.com/. The program outputs a concise summary to the console, including throughput and latency distribution. Some users employ wrk as part of broader performance-testing workflows to compare server configurations, load balancers, or CDN endpoints.

Limitations are that wrk focuses on HTTP benchmarking and may not replace full-fledged load-testing suites for complex scenarios. It is valued for its speed, simplicity, and scriptable workload generation, making it a staple tool in web performance testing.