HTTP caching

Rails >= 3 comes with HTTP caching abilities out of the box. This uses the Cache-Control and ETag headers to control how long a client or intermediary (such as a CDN) can cache a page.

In a controller action, use expires_in to set the length of caching for that action:

def show
  @user = User.find params[:id]
  expires_in 30.minutes, :public => true
end

Use expires_now to force immediate expiration of a cached resource on any visiting client or intermediary:

def show
  @users = User.find params[:id]
  expires_now if params[:id] == 1
end