What's the difference between Rack and Passenger?

Question

I'm trying to deploy a Sinatra app to Dreamhost and it says the following:

Since DH supports Passenger, which in turn supports Rack-based ruby applications, DH does indeed support Sinatra.

I'm having difficulty parsing that statement - what's the difference between Rack and Passenger (and why is Sinatra "Rack-based")?

Psychosomatics

Answer 1

Rack is a standardized API for web servers to talk to middleware and web frameworks in Ruby. Phusion Passenger is an Apache module that implements the Rack API. Sinatra is a web framework that is built on top of the Rack API, so because Dreamhost supports Phusion Passenger, that means that it supports Rack, and thus Sinatra.

Modulus