// the find
defunkt/unicorn
Unofficial Unicorn Mirror.
unicorn is a Rack HTTP server for Ruby apps that only handles fast, low-latency clients and relies on a reverse proxy (nginx) for anything else. It's aimed at Rails/Rack deployments that want OS-level process management and load balancing rather than an in-process solution like Puma.
Forking worker model with kernel-based load balancing means slow or crashed workers don't block others, and there's no in-process concurrency to reason about. Zero-downtime binary upgrades and USR1 log reopening are genuinely useful ops features that a lot of newer servers still lack. The C extension for HTTP parsing (ragel-generated) is fast and battle-tested from over a decade of production use.
No threading support at all, so it's a poor fit for I/O-bound apps unless you run a large number of processes, which costs memory. Requires a C compiler and Ruby dev headers to install, and the docs assume you already know why you'd choose this over Puma. The README itself calls the project actively harmful to the Ruby ecosystem and discourages new usage, which is a strange sell for anyone evaluating it today, and the project is effectively in maintenance mode with mailing-list-only support.