Rainbows! is an HTTP server for sleepy Rack applications. It is based on Unicorn, but designed to handle applications that expect long request/response times and/or slow clients. For Rack applications not heavily bound by slow external network dependencies, consider Unicorn instead as it simpler and easier to debug.

Rainbows is mainly designed for the odd things Unicorn sucks at:

• Web Sockets (via Sunshowers)
  
• 3rd-party APIs (to services outside your control/LAN)
  
• OpenID consumers (to providers outside your control/LAN)
  
• Reverse proxy implementations with editing/censoring (to upstreams outside your control/LAN)
  
• Comet
  
• BOSH (with slow clients)
  
• HTTP server push
  
• Long polling
  
• Reverse AJAX
  
• real-time upload processing (via upr)
  Rainbows can also be used to service slow clients directly even with fast applications. 
  
  

 You may also install it via RubyGems on RubyGems.org

gem install rainbows

for Rack applications

In APP_ROOT, run:

rainbows

PS: For more information about tunning you can read here