Yarn is a multi-threaded webserver written in Ruby 1.9 by Jesper Kjeldgaard. It handles concurrent requests by means of a set of workers and a job queue for incomming requests.
gem install yarn
To use Yarn with Rack applications:
rackup -s Yarn <rackup file (config.ru)>
To use Yarn for serving static and ruby (*.rb) files:
yarn [options] where [options] are: --host, -h <s>: Hostname or IP address of the server (default: 127.0.0.1) --port, -p <i>: Port number to listen on for incomming requests (default: 3000) --workers, -w <s>: Number of worker threads (default: 32)