JRuby is undoubtedly the most mature of the alternative Ruby implementations. Supporting Ruby 1.8.7 and 1.9.1 (mostly!) and JIT compilation, JRuby is already in use in mission critical Ruby apps and runs scarily fast on the JVM. In this interview with JRuby core member, Charles Nutter, we dig deep into what makes JRuby tick.

The current JRuby team members are all passionate hackers with intimate knowledge of Ruby, Java, and of course JRuby. That said, none of us were on the team at the project’s original inception. I assume the JRuby pioneers thought JRuby would be a good idea—I know I did, when I first heard about it. For a lot of folks though, it’s somewhat less obvious. Why is writing JRuby on top of the JVM a good idea, they ask. Are we nuts, evil geniuses, or is using the JVM just a solid pragmatic decision?

There are two main types of scalability: vertical and horizontal. Vertical scalability consists of potentiating the hardware specs of a given server. This is typically done by increasing the number (and to a minor extent, speed) of the processors, adding more RAM, and so on. Commodity hardware tends to impose a strong limit on the resources that can be augmented. There is only so much that can be stuffed into your typical x64_86 Dell server, even replacing the entire machine with the top of the line model (having the same architecture).

There is major news in Rubyland today. MacRuby’s team just released their fist beta of version 0.5 (an experimental, still incomplete version of Ruby), which brings JIT, removal of the dreaded GIL (Global Interpreter Lock), native threads, GCD (Grand Central Dispatch) for multicore computing, and a whole new set of features found in the release announcement to the table.