rails 3.1 realtime update feature

Using ajax: rails 3.1 realtime update feature on newest questions tagged ajax – Stack Overflow

I’ve seen many sites that their messages feed is keep sliding down incessantly.
For example: the previous version of twitter and now the foursquare. How to do that?

Moreover, I also want to know how to implement meetup’s RSVP instant push in rails, they update it by seconds?

Thanks.

source: http://stackoverflow.com/questions/7687663/rails-3-1-realtime-update-feature
Using ajax: using-ajax