Does each ip request to a ruby on rails application on a server spawn a new ruby process?

When I view the output of the top command on ubuntu, I notice sometimes there is 6 ruby processes. When are each of these processes spawned?

I cannot imagine that it’s every time someone loads the rails application from a different ip address, otherwise I would assume there would be more ruby processes spawned.

In whatever is managing your Rails app, there's probably a setting for number of workers. These can be dynamic, or not, depending. Multiple workers running your Rails app is pretty standard, actually, to respond to multiple requests. This is something you see all the time with apache, nginx, lighty, fastcgi and other things as well.