Session breaks when use subdomains with dalli store in rails3

I tried to use :domain => :all in session_store.rb and config.action_controller.session = {:domain => '.mydomain.com'} but anyway session breaks when i visit mydomain.com after w开发者_如何学Goww.mydmain.com.

Any suggestions?

SubdomainFu.configure do |config|
  config.tld_size = 2
  config.preferred_mirror = 'www'
end

Try with these configurable options. I hope it helps you.