I believe Mongrel2 (http://mongrel2.org http://mongrel2.org) is close to what you're talking about. It uses zeromq (http://www.zeromq.org http://www.zeromq.org)

I believe Mongrel2 (http://mongrel2.org http://mongrel2.org) is close to what you're talking about. It uses zeromq (http://www.zeromq.org http://www.zeromq.org) to talk to a backend application and the backend application talks back to the web server using the same protocol. Not exactly nodes pulling messages off a queue, but closer to something like that?