Application Servers

Itsi – high-performance web and application server

Itsi is a high-performance web and application server with first-class support for Ruby applications. It is a Rack-compliant server that can also operate as a reverse proxy, API gateway, gRPC server, and static file server.

The software combines a Rust-powered server core with an expressive Ruby configuration API and DSL.

This is free and open source software.

Key Features

  • Runs Rack-compatible Ruby applications and middleware.
  • Serves static files with caching, range requests, automatic indexes, and fallback routing.
  • Operates as a reverse proxy with load balancing, failover, and automatic retries.
  • Provides HTTP/1.1, HTTP/2, WebSocket, and gRPC support.
  • Offers a gRPC and REST compatibility layer for JSON clients.
  • Supports gzip, Brotli, Zstandard, deflate, and streaming compression.
  • Automates TLS certificate provisioning with Let’s Encrypt.
  • Provides JWT, API key, and HTTP Basic authentication.
  • Includes rate limiting, IP access controls, and intrusion protection.
  • Supports zero-downtime configuration reloads and phased restarts.
  • Runs multiple workers to take advantage of multicore systems.
  • Offers non-blocking concurrency through Ruby’s Fiber Scheduler.
  • Provides structured logging, request logging, and status reporting.
  • Uses a Ruby configuration API and domain-specific language.

Website: github.com/wouterken/itsi
Support:
Developer: Wouter Coppieters
License: GNU Lesser General Public License v3.0

Itsi is written in Rust and Ruby. Learn Rust with our recommended free books and free tutorials. Learn Ruby with our recommended free books and free tutorials.


Related Software

Ruby Application Servers
PumaConcurrent web server for Ruby and Rack
Phusion PassengerWeb server and application server for Ruby, Python and Node.js
unicornHTTP server for Rack applications
Rainbows!HTTP server for sleepy Rack applications based on Unicorn
yahnsSleepy, multi-threaded, non-blocking application server for Ruby

Read our verdict in the software roundup.


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