Is there a gem for threadpooling anyone can recommend?
From my experience forking/process pooling is much more effective than thereadpooling in Ruby (assuming you do not need much in terms of thread communication). Some time ago I created a gem called process_pool, which is a very basic process pool with a file based job queue (you can check it out here: http://github.com/psyho/process_pool).
I would try https://github.com/ruby-concurrency/concurrent-ruby/ .
It's basically a port of the java.util.concurrent abstractions (including threadpools) to ruby -- except if you install it under Jruby, it'll use the java.util.concurrent stuff. So you can write code that'll work and do the same thing semantically (not neccesarily the same performance) under any ruby platform.
It also offers Futures, a higher level abstraction which may be more convenient to use than thread pools.