The State of JRuby

It's been sort of quiet on the JRuby front for a few weeks, so I thought I'd give a heads up on what things we're working on at the moment. At the moment, we're planning to release 0.9.9 sometime next week. At that point, several things we're working on right now should be fixed.

• There is a problem with deterministic threading in JRuby, which results in timeout errors sometimes escaping out of their rescue nodes. This is very serious for long running applications and Charles is hard at work providing better Thread semantics for us. The problem is that it's very hard to match MRI's green thread functionality with real native threads.
• Thomas is hard at work with one of his gigantic refactorings. This time the goal is to remove most of ThreadContext and make many parts of the call chain and block invocation chains easier to work with.
• Marcin have been working for some weeks now on a port of the hash implementation in MRI, and a corresponding rewrite of RubyHash. At the same time, he's hard at work rewriting RubyString to allow COW (copy-on-write) semantics. This could potentially improve performance and also make JRuby less memory intense.
• Earlier this week, we identified and fixed two very serious memory leaks. The second of these caused large leakage in all Rails applications using Cgi::Session for session data (which is almost all JRuby on Rails applications, except those running in Rails-integration). At the moment we don't see any leaking for Rails applications, so the situation looks good. (Both of these leaks were found with the help of Java monitoring tools, like JConsole, jmap and jhat. Very useful things.)
• I have been doing some serious YAML fixes these last days, with the result that our YAML situation is better than ever. It even handles recursive objects correctly. (Which is a pain in Java. In C it's easy, though.)

Overall, we're working very hard on the last, quirky compatibility issues right now; we have a few different, large Rails applications that we use to identify strange issues. And also, more and more people are trying their applications on JRuby, which means we get better (and more) bug reports. This is really great.

After 0.9.9 has been released, we're planning on finishing up remaining important bugs. I'm also very keen about getting more databases running really well with Rails. We will try to get Continous Integration set up for these too.