Serving multiple Rails applications through one ruby interpreter instance

Question

Given that each Ruby-On-Rails application needs at least about 40MBs of memory, I was wondering if there is a way of running multiple rails-application instances (different ones) over one interpreter of Ruby so that all shared libraries (rmagick etc) are shared between different application instances, saving space.

If that would be possible, then, I could be running 5-6 rails applications in a single 256RAM virtual server.

Is that possible?

Answer 1

I don't think this is possible without substantially changing the current code base.

But all is not lost.

If these websites are fairly low traffic and you have a fast vps you should take in mind that mod passenger drops the instances from memory if they're inactive for a while. So in theory you could run an unlimited amount of applications as long as you only have a few active at the same time. The price is a slower response on the first request that loads the instance.

Answer 2

Another option would be to load all the shared libraries, then fork off as many child processes as you have apps (use Process.fork ) and run a different app in each child.

Pages of memory which are only read and not written will be shared between the parent and child processes.