Is puma the ONLY multi-threaded rails 4 http server?

Question

I've gotten our stack converted to Rails 4 (yea!)

and I'm looking to take advantage of the thread-safe code.

Puma works in getting up, stopping it appears to be a different problem :(

Is Puma the only multi-threaded rails?

Thin -> EventMachine
Unicorn -> Forking
Puma -> multi-threaded

Mongrel -> don't care
Webbrick -> don't care

Answer 1

No. In alphabetical order:

• Iodine a HTTP / Websocket Server & EventMachine alternative (kqueue/epoll based)
• Net::HTTP::Server, despite the lack of advertising, supports multithreading
• Phusion Passenger has supported multithreading since v4 beta
• Rainbows! supports multiple concurrency models, including multithreading
• Reel is a Celluloid-backed "evented" server, which "also works great for multithreaded applications and provides traditional multithreaded blocking I/O support too"
• Thin has a threaded mode, which can be enabled by passing --threaded or by setting threaded: true in the appropriate configuration file (e.g. bundle exec thin start --threaded)
• WEBrick is on its own multithreaded, so it's not fair to eliminate it as an option; if you're using the Rails-embedded version, you'll need to monkey-patch Rails::Server to enable multi-threading
• Zbatery is based on Rainbows! and supports all concurrency models that Rainbows! supports

Note that currently MRI Ruby runs only one thread runs at a time due to its global interpreter lock (GIL). You'll only be truly able to exploit multithreading by using a different Ruby runtime such as JRuby or Rubinius, which provide access to native threads. If you decide to go with JRuby, there are several JVM-dependent servers worth exploring.