Rack Delegate

Rack level reverse proxy. Route requests to services with pure Ruby if that's your boat. The boat won't be pretty fast, but you can deploy it on your Heroku's, and what-not-fancy-cloud-services, without a bit of complications.

The proxy can sit after the request authentication, or before it, depending on the services you have to route requests to. You can rewrite requests URLs, and even the whole Net::HTTP::Reqest to be sent out.

Installation

Put this in the application Gemfile:

gem 'rack-delegate'

rack-delegate requires Ruby 2.0 and above.

Usage

To use rack-delegate, you first need to configure a delegator proxy. You can do that with Rack::Delegate.configure. Note that Rack::Delegate.configure, actually creates a middleware, which we can insert in an arbitrary stack later on.

Macro::ApiGateway = Rack::Delegate.configure do
  # Strips the leading /api out of the outgoing requests.
  rewrite { path.gsub!(%r{\A/api}, '') }

  # Don't proxy requests without them matching on the condition in the block.
  constraints { |request| Version.new('v1').matches?(request) }

  # With the rewrite on, requests you /api/users will go to
  # http://users-service.intern/users.
  from %r{\A/api/users},    to: 'http://users-service.intern'

  # Requests go to http://payments-service.intern/payments.
  from %r{\A/api/payments}, to: 'http://payments-service.intern'
end

module Macro
  class Appplication
    middleware.use ApiGateway
  end
end

Yes, you can insert multiple Rack::Delegate middleware instances in your stack. Say, one for requests that don't require authentication and one for requests that do.

(Given that the request authentication is a middleware itself.)

Macro::UnauthenticatedGateway = Rack::Delegate.configure do
  rewrite { path.gsub!(%r{\A/api}, '') }

  from %r{\A/registration}, to: 'http://registration-service.intern'
end

Macro::AuthenticatedGateway = Rack::Delegate.configure do
  rewrite { path.gsub!(%r{\A/api}, '') }

  from %r{\A/api/users},    to: 'http://users-service.intern'
  from %r{\A/api/payments}, to: 'http://payments-service.intern'
end

module Macro
  class Appplication
    middleware.insert_before "Auth", UnauthenticatedGateway
    middleware.insert_after "Auth", AuthenticatedGateway
  end
end

Why

A question well asked, dear sir! Going micro-services early may bite you. Going micro-services for the sake of it may bite you. Going micro-services, because you can't manage that shitty app, well... may result in shitty services as well.

Anyway, if you wanna go that route, you can do it quickly with Ruby and prototype. And if you do, you may as well need a better API gateway than this one. OpenResty may be useful for you.