A transparent streaming proxy to be used as rack middleware.

  • Streams the response from the downstream server to minimize memory usage
  • Handles chunked encoding if used
  • Proxies GET/PUT/POST/DELETE, XHR, and cookies

Now updated to be compatible with Rails 3 and 4, and fixes major concurrency issues that were present in 1.0.

Use Rack::StreamingProxy when you need to have the response streamed back to the client, for example when handling large file requests that could be proxied directly but need to be authenticated against the rest of your middleware stack.

Note that this will not work well with EventMachine. EM buffers the entire rack response before sending it to the client. When testing, try Unicorn or Passenger rather than the EM-based Thin (See discussion).

A simple streamer app has been included for testing and development.


To use inside a Rails app, add a config/initializers/streaming_proxy.rb initialization file, and place in it:

require 'rack/streaming_proxy'

YourRailsApp::Application.configure do
  config.streaming_proxy.logger             = Rails.logger                          # stdout by default
  config.streaming_proxy.log_verbosity      = Rails.env.production? ? :low : :high  # :low or :high, :low by default
  config.streaming_proxy.num_retries_on_5xx = 5                                     # 0 by default
  config.streaming_proxy.raise_on_5xx       = true                                  # false by default

  # Will be inserted at the end of the middleware stack by default.
  config.middleware.use Rack::StreamingProxy::Proxy do |request|

    # Inside the request block, return the full URI to redirect the request to,
    # or nil/false if the request should continue on down the middleware stack.
    if request.path.start_with?('/search')

To use as a Rack app:

require 'rack/streaming_proxy'

use Rack::StreamingProxy::Proxy do |request|
  if request.path.start_with?('/proxy')
    # You probably want to get rid of the '/proxy' in the path, when requesting from the destination.
    proxy_path = request.path.sub %r{^/proxy}, ''


Add this line to your application's Gemfile:

gem 'rack-streaming-proxy'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-streaming-proxy


  • Ruby = 1.9.3
  • rack >= 1.4
  • servolux ~> 0.10

These requirements (other than Ruby) will be automatically installed via Bundler.

This gem has not been tested with versions lower than those indicated.

This gem works with Ubuntu 10.04. It has not been tested with later versions of Ubuntu or other Linuxes, but it should work just fine. It has not been tested with OS X but should work as well. However, I doubt it will work on any version of Windows, as it does process-based stuff. You are most welcome to try it and report back.


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Implement your changes, and make sure to add tests!
  4. Commit your changes (git commit -am 'Add some feature')
  5. Push to the branch (git push origin my-new-feature)
  6. Create new Pull Request

Thanks To