hey

Product Introduction

1. Definition: Hey is a modern, open-source HTTP load testing and benchmarking tool written in Go. It is a command-line utility designed to generate significant web traffic to evaluate server performance.
2. Core Value Proposition: Hey exists to provide a more user-friendly, feature-rich, and modern alternative to traditional load testing tools like ApacheBench (ab). It solves the problem of needing a powerful yet accessible tool for developers and DevOps engineers to conduct performance testing, stress testing, and scalability analysis of web applications, APIs, and microservices.

Main Features

1. Configurable Load Generation: Users can precisely define the volume and concurrency of HTTP requests. The -n flag sets the total number of requests, while -c defines the number of concurrent workers (virtual users) executing them. This allows for simulating realistic user traffic patterns, from low-volume functional tests to high-concurrency stress tests.
2. Duration-Based and Rate-Limited Testing: Beyond a fixed request count, Hey supports duration-based tests (-z flag) for sustained load over time (e.g., -z 5m). Crucially, it includes a rate-limiting feature (-q flag) to cap the queries per second (QPS) per worker, enabling precise throughput control and preventing unintentional denial-of-service attacks during testing.
3. Comprehensive HTTP/1.1 and HTTP/2 Protocol Support: Hey supports a wide array of HTTP methods (GET, POST, PUT, etc.) and allows full customization of requests with headers (-H), body data (-d, -D), authentication (-a), and content types (-T). It natively supports HTTP/2 (-h2), enabling performance benchmarking of modern servers using this more efficient protocol. Additional controls like disabling compression or keep-alive connections allow for fine-grained network behavior testing.
4. Detailed Performance Metrics Output: After a test run, Hey provides a concise statistical summary including total time, requests per second, average/mean latency, and latency distribution percentiles (50th, 75th, 90th, 99th). For deeper analysis, it can export raw metrics in CSV format (-o csv), which can be imported into data visualization tools for trend analysis and reporting.

Problems Solved

1. Pain Point: The limitations and outdated user experience of older benchmarking tools like ApacheBench (ab), which often lack features for modern web development, such as HTTP/2 support, flexible request customization, and easy rate limiting.
2. Target Audience: Backend Developers, DevOps Engineers, Site Reliability Engineers (SREs), and Performance Testers who are responsible for ensuring the reliability, speed, and scalability of web services, REST APIs, and GraphQL endpoints.
3. Use Cases: Conducting capacity planning before a product launch; identifying performance bottlenecks and latency issues in a staging environment; comparing the performance impact of different software deployments or infrastructure changes; validating autoscaling rules for cloud infrastructure; performing simple smoke tests and synthetic monitoring.

Unique Advantages

1. Differentiation: Compared to ApacheBench, Hey offers a significantly better developer experience with more intuitive flags, HTTP/2 support, and rate limiting. Compared to more complex frameworks (e.g., JMeter), Hey is far simpler to install and use for quick, scriptable command-line tests, making it ideal for CI/CD pipeline integration.
2. Key Innovation: Its simplicity and single-binary deployment. Written in Go, Hey compiles into a standalone executable with zero external dependencies, making installation and distribution trivial across Linux, macOS, and Windows. This "just works" philosophy lowers the barrier to entry for performance testing.

Frequently Asked Questions (FAQ)

1. How do I install the Hey HTTP load testing tool on macOS? The easiest method is via Homebrew: run brew install hey. Alternatively, download the pre-compiled hey_darwin_amd64 binary from the official GitHub releases, make it executable (chmod +x), and move it to your PATH.
2. What is the difference between Hey and ApacheBench (ab) for performance testing? Hey is a modern alternative to ab with key advantages: native HTTP/2 support, the ability to limit request rate (QPS), more informative output with latency percentiles, easier request body and header customization, and duration-based testing in addition to fixed request counts.
3. Can I use Hey to test a POST API endpoint with JSON data? Yes. Use the -m POST flag, set the Content-Type header with -H "Content-Type: application/json", and pass the JSON string with the -d flag, for example: hey -m POST -H "Content-Type: application/json" -d '{"key":"value"}' http://api.example.com/endpoint.
4. How do I interpret the results and latency metrics from a Hey load test? Focus on Requests/sec (throughput), Average latency, and the tail latencies (99%). A high Requests/sec with low average latency is good. A high 99% latency (e.g., 2 seconds) indicates that 1% of user requests were very slow, highlighting a potential performance bottleneck that needs investigation.
5. Is Hey suitable for running a long-duration stress test or soak test? Yes. Use the -z flag to specify a duration (e.g., -z 1h). Combine this with the -c (concurrency) and -q (rate limit) flags to apply a sustained, realistic load on your application for an extended period to uncover memory leaks or infrastructure degradation.