# oha — HTTP Load Generator with Real-Time TUI Dashboard

> HTTP load generator written in Rust with a beautiful real-time terminal UI for visualizing request latency and throughput.

## Install

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# oha — HTTP Load Generator with Real-Time TUI Dashboard

## Quick Use
```bash
# Install via cargo
cargo install oha

# Install via Homebrew
brew install oha

# Basic load test: 200 requests, 50 concurrent
oha -n 200 -c 50 http://localhost:8080/

# Run for 30 seconds with real-time TUI
oha -z 30s -c 100 http://localhost:8080/
```

## Introduction
oha is an HTTP load generator written in Rust that provides a real-time terminal user interface showing live latency histograms, status code distributions, and throughput metrics as the test runs. Inspired by rakyll/hey, it adds visual feedback so you can observe server behavior under load without waiting for a final summary. The Rust implementation ensures low resource consumption on the client side even at high concurrency levels.

## What oha Does
- Sends configurable HTTP load with fixed request count or duration-based runs
- Displays a real-time TUI with live latency histogram, percentiles, and error rates
- Supports HTTP/1.1 and HTTP/2 with custom headers, methods, and request bodies
- Outputs final results as text, JSON, or compatible formats for CI integration
- Handles TLS connections with configurable certificate options

## Architecture Overview
oha uses Tokio as its async runtime to manage thousands of concurrent connections efficiently. Each connection runs as an independent async task sending requests and recording response times. A dedicated TUI thread powered by ratatui reads timing data from a shared buffer and renders live charts at a fixed refresh rate. After the run completes, oha aggregates all samples and prints a statistical summary including percentiles, mean, and standard deviation.

## Self-Hosting & Configuration
- Install via `cargo install oha` or `brew install oha` on macOS
- Pre-built binaries available on GitHub Releases for Linux, macOS, and Windows
- Use `-n` for total request count or `-z` for duration-based runs (e.g., `-z 60s`)
- Set `-c` for concurrent connections and `-q` for per-second rate limiting
- Disable the TUI with `--no-tui` for headless CI environments and pipe JSON output with `-j`

## Key Features
- Real-time terminal dashboard with live latency histogram and throughput graph
- Written in Rust for minimal memory footprint and maximum client-side efficiency
- Supports both HTTP/1.1 and HTTP/2 protocols out of the box
- JSON output mode for programmatic consumption in CI/CD pipelines
- Cross-platform: runs natively on Linux, macOS, and Windows

## Comparison with Similar Tools
- **hey** — simpler text-only output with no live dashboard; oha adds real-time visualization
- **wrk** — higher raw throughput via C/epoll but no TUI and Unix-only; oha is cross-platform
- **bombardier** — Go-based with a progress bar; oha offers a richer TUI with histograms
- **k6** — scriptable in JavaScript with cloud reporting; oha is a lightweight single-purpose tool
- **Vegeta** — constant-rate attack model with plot output; oha provides live interactive feedback

## FAQ
**Q: Can I disable the TUI for CI usage?**
A: Yes. Pass `--no-tui` to get a simple text summary, or `-j` for JSON output suitable for automated parsing.

**Q: Does oha support HTTP/2?**
A: Yes. Use `--http2` to force HTTP/2 connections, or let oha negotiate via ALPN automatically.

**Q: How does oha compare to wrk in throughput?**
A: wrk typically achieves higher raw RPS due to its C/epoll design. oha trades some peak throughput for a richer user experience and cross-platform support.

**Q: Can I send POST requests with a body?**
A: Yes. Use `-m POST -d '{"key":"val"}'` or `-D @body.json` to load the body from a file.

## Sources
- https://github.com/hatoo/oha
- https://github.com/hatoo/oha/blob/master/README.md

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Source: https://tokrepo.com/en/workflows/54453dda-41af-11f1-9bc6-00163e2b0d79
Author: AI Open Source