Rack is Ruby’s answer to Python’s WSGI.
A year and half later, Rails replaced the guts of
script/server with a call out to Rack.
Days later, Phusion Passenger™ essentially became mod_rack, though you can still call it mod_rails if you like.
Yesterday, a new micro-framework named Metal has been introduced which allows one to intercept requests, whether it be for performance reasons or simply to call out to another framework. Sinatra has already been demonstrated, Merb can’t be far behind.
I love it when a plan comes together