example_service_proxy.rb

# frozen_string_literal: true

###
# This is an example of how to use Rack-Proxy in a Rails application.
#
# Setup:
# 1. rails new test_app
# 2. cd test_app
# 3. install Rack-Proxy in `Gemfile`
#    a. `gem 'rack-proxy', '~> 2.0'`
# 4. install gem: `bundle install`
# 5. copy this class into your app (e.g. `app/middleware/example_service_proxy.rb`)
#    and mount it from `config/initializers/proxy.rb`
# 6. run: `SERVICE_URL=http://guides.rubyonrails.org rails server`
# 7. open in browser: `http://localhost:3000/example_service`
#
###
ENV["SERVICE_URL"] ||= "http://guides.rubyonrails.org"

class ExampleServiceProxy < Rack::Proxy
  def perform_request(env)
    request = Rack::Request.new(env)

    # use rack proxy for anything hitting our host app at /example_service
    if %r{^/example_service}.match?(request.path)
      backend = URI(ENV["SERVICE_URL"])
      # most backends required host set properly, but rack-proxy doesn't set this for you automatically
      # even when a backend host is passed in via the options
      env["HTTP_HOST"] = backend.host

      # This is the only path that needs to be set currently on Rails 5 & greater
      env["PATH_INFO"] = ENV["SERVICE_PATH"] || "/configuring.html"

      # don't send your sites cookies to target service, unless it is a trusted internal service that can parse all your cookies
      env["HTTP_COOKIE"] = ""
      super
    else
      @app.call(env)
    end
  end
end

# Only wire into the middleware stack when running inside a booted Rails app, so
# this file is safe to require anywhere (doc/RBI tooling, a stray require) without
# crashing or silently installing a proxy.
if defined?(Rails) && Rails.respond_to?(:application) && Rails.application
  Rails.application.config.middleware.use ExampleServiceProxy, backend: ENV["SERVICE_URL"], streaming: false
end