A Reverse Proxy for Rack

This is a simple reverse proxy for Rack that pretty heavily rips off Rack Forwarder. It is not meant for production systems (although it may work), as the webserver fronting your app is generally much better at this sort of thing.

Installation

The gem is available on rubygems. Assuming you have a recent version of Rubygems you should just be able to install it via:

gem install rack-reverse-proxy

For your Gemfile use:

gem "rack-reverse-proxy", require: "rack/reverse_proxy"

Usage

Rack::ReverseProxy should ideally be the very first middleware in your stack. In a typical use case it is being used to proxy an entirely different website through your application, so it's unlikely that you will want any other middleware to modify the requests or responses. The examples below reflect this.

Generic Rack app example

require 'rack/reverse_proxy'

use Rack::ReverseProxy do
  # Set :preserve_host to true globally (default is true already)
  reverse_proxy_options preserve_host: true

  # Forward the path /test* to http://example.com/test*
  reverse_proxy '/test', 'http://example.com/'

  # Forward the path /foo/* to http://example.com/bar/*
  reverse_proxy /^\/foo(\/.*)$/, 'http://example.com/bar$1', username: 'name', password: 'basic_auth_secret'
end

app = proc do |env|
  [ 200, {'Content-Type' => 'text/plain'}, ["b"] ]
end
run app

Ruby on Rails app example

This example use config.middleware.insert(0 to ensure that Rack::ReverseProxy is first in the stack. It is possible that other code in your app (usually in application.rb, development.rb, or production.rb) will take over this position in the stack. To ensure that this is not the case, view the stack by running rails middleware. You should see Rack::ReverseProxy at the top. Note that the middleware stack will likely differ slightly in each environment. All that said, it's a pretty safe bet to put the below code into application.rb.

# config/application.rb
config.middleware.insert(0, Rack::ReverseProxy) do
  reverse_proxy_options preserve_host: true
  reverse_proxy '/wiki', 'http://wiki.example.com/'
end

Rules

As seen in the Rack example above, reverse_proxy can be invoked multiple times with different rules, which will be commulatively added.

Rules can be a regex or a string. If a regex is used, you can use the subcaptures in your forwarding url by denoting them with a $.

Right now if more than one rule matches any given route, it throws an exception for an ambiguous match. This will probably change later. If no match is found, the call is forwarded to your application.

Options

reverse_proxy_options sets global options for all reverse proxies. Available options are:

• :preserve_host Set to false to omit Host headers
• :username username for basic auth
• :password password for basic auth
• :matching is a global only option, if set to :first the first matched url will be requested (no ambigous error). Default: :all.
• :timeout seconds to timout the requests
• :force_ssl redirects to ssl version, if not already using it (requires :replace_response_host). Default: false.
• :verify_mode the OpenSSL::SSL verify mode passed to Net::HTTP. Default: OpenSSL::SSL::VERIFY_PEER.
• :x_forwarded_headers sets up proper X-Forwarded-* headers. Default: true.
• :stripped_headers Array of headers that should be stripped before forwarding reqeust. Default: nil. e.g. stripped_headers: ["Accept-Encoding", "Foo-Bar"]

If reverse_proxy_options is invoked multiple times, the invocations will have a commulative effect, only overwritting the values which they specify. Example of how this could be useful:

config.middleware.insert(0, Rack::ReverseProxy) do
  reverse_proxy_options preserve_host: false
  if Rails.env.production? or Rails.env.staging?
    reverse_proxy_options force_ssl: true, replace_response_host: true
  end
  reverse_proxy /^\/blog(\/?.*)$/, 'http://blog.example.com/blog$1'
end

Note on Patches/Pull Requests

• Fork the project.
• Make your feature addition or bug fix.
• Add tests for it. This is important so I don't break it in a future version unintentionally.
• Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
• Send me a pull request. Bonus points for topic branches.

Contributors

• Jon Swope, creator
• Oleksii Fedorov, maintainer