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Daniel Doubrovkine

aka dB., @awscloud, former CTO @artsy, +@vestris, NYC

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tl;dr – the source is here

Here’s how I mount a Grape API on Rack and also serve static pages. Most useful for building a service with documentation.

Setup bundler with the required gems. I am using the next version of Grape (frontier branch and the next version of rack-contrib which contains _Rack::TryStatic _that we’re going to want to use).

source "https://rubygems.org"

gem "rack", "1.3.5"
gem "rack-contrib", :git => "https://github.com/rack/rack-contrib.git", :require => "rack/contrib"
gem "grape", :git => "https://github.com/ruby-grape/grape.git", :branch => "frontier"

Static content goes to a new public folder, for example public/index.html.

Our application will need to boot with all these gems, we’ll do it Rails-style by starting with a config/boot.rb file. It brings in Bundler.

require 'rubygems'
require 'bundler/setup'

Let’s define our Acme Grape API that will have a system resource that answers ping requests with “pong”. _This goes into _api/api.rb.

module Acme
  class API < Grape::API
    version 'v1', :using => :header, :vendor => 'acme', :format => :json
    resource :system do
      desc "Returns pong."
      get :ping do

The application requires Bundler, all the gems in Gemfile and our API. Let’s define it in config/application.rb.

require File.expand_path('../boot', __FILE__)

Bundler.require :default, ENV['RACK_ENV']

require File.expand_path('../../api/api', __FILE__)

Note the odd File.expand_path construct, borrowed from Rails, - it translates a relative path to the current file into an absolute path, there’re allowing us to run the application from any directory – useful for hosting where you never know who boots the application.

Continuing to borrow from Rails, we will want different environments (development, production, etc.), so it’s a good idea to keep things organized. Setup the environment in _config/environment.rb _and then load the application.

ENV['RACK_ENV'] ||= :test

require File.expand_path('../application', __FILE__)

Finally, we need to “rackup” this whole thing in config.ru. We will use Rack::TryStatic to serve static pages when available and pass through to the Acme API otherwise.

require File.expand_path('../config/environment', __FILE__)

use Rack::TryStatic,
  :root => File.expand_path('../public', __FILE__),
  :urls => %w[/], :try => ['.html', 'index.html', '/index.html']

run Acme::API

Run the application with bundle exec rackup.

Full source on Github.