Nginx Unit — Dynamic Polyglot Application Server

Introduction

Nginx Unit is an application server built by the Nginx core team that can run applications in multiple languages simultaneously. Configuration is managed through a RESTful JSON API, allowing you to add routes, change listeners, and deploy new app versions without restarts or dropped connections.

What Nginx Unit Does

• Serves applications written in Python, PHP, Go, Node.js, Java, Ruby, Perl, and WebAssembly
• Provides a RESTful JSON API for runtime configuration without server restarts
• Routes requests by URI, host, method, headers, and other properties
• Handles TLS termination with automatic certificate management
• Serves static files alongside dynamic applications in a single server

Architecture Overview

Unit uses a multi-process architecture with a controller process that owns the config API and router processes that handle incoming connections. Each application language runs in isolated worker processes managed by language-specific modules. Configuration changes are applied atomically: the controller validates the new config, forks new workers, drains old ones, and swaps routing tables with zero downtime.

Self-Hosting & Configuration

• Install from the official repository for your OS or run the Docker image docker run -d unit
• Send JSON configuration to the control socket at /var/run/control.unit.sock
• Define listeners, routes, and applications in a single JSON document
• Update any subtree of the config with PUT, PATCH, or DELETE requests
• TLS certificates are uploaded as PEM bundles via the /certificates API endpoint

Key Features

• Zero-downtime configuration: changes apply without connection drops
• Per-application process isolation with configurable worker counts
• Built-in request routing with pattern matching and header-based rules
• Static file serving with MIME type detection and directory listings
• Native WebAssembly support via the Wasm component model

Comparison with Similar Tools

• Nginx — reverse proxy and static server; Unit adds native multi-language app serving with a config API
• Apache — venerable multi-module server; Unit offers simpler dynamic configuration and polyglot support
• Gunicorn — Python-only WSGI server; Unit handles multiple languages in one process tree
• Caddy — automatic HTTPS reverse proxy; Unit focuses on application serving rather than proxying

FAQ

Q: Can Unit replace Nginx as a reverse proxy? A: Unit can proxy and serve apps, but Nginx remains stronger for complex proxy scenarios like load balancing pools and caching. They are often used together.

Q: How do I deploy a new app version without downtime? A: PUT the updated application config to the API. Unit spins up new workers, waits for in-flight requests to finish on old workers, then shuts them down.

Q: Does Unit support HTTP/2? A: Yes. HTTP/2 is supported on TLS listeners. HTTP/3 (QUIC) support is in development.

Q: What operating systems are supported? A: Unit runs on Linux, FreeBSD, and macOS. Official packages are available for major Linux distributions. Docker images are also provided.

Sources

• https://github.com/nginx/unit
• https://unit.nginx.org/