Ruby on Rails: how to extract part of web-app?

I have a big application and I need to extract part of this application to separate small application. I'm going to develop big application, but I want to small app to be up to date.

What should I use for this p开发者_开发百科urpose?

P.S. I use Ruby on Rails 3

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There are two approaches you could consider.

• Rails Engines
• Rack Middleware

The new router in Rails 3 offers some very powerful facilities for routing to rack applications embedded with the application