JRuby Serial Interview 1

Posted by Nick Sieger Sat, 06 Jan 2007 18:21:56 GMT

In cooperation with Pat Eyler, we present this conversation as a parallel thread to his recent string of Rubinius “serial” (ongoing) interviews. We aim to bring short, frequent, looks at the two alternate Ruby implementations’ developments, and have the conversations intersect from time to time.

A lot has happened since the last JRuby interview with Pat -- Java was open-sourced, you’ve been to Javapolis, pushed out another release, and a slew of new contributions have poured in. How have your plans and goals for JRuby changed (if at all) since then?

Charles Nutter: For me the biggest items are the following, in order:

  • We need to announce full Rails support as soon as possible
  • We need to resolve the remaining runtime performance bottlenecks
  • We need to keep working on the compiler

All these of these have been the hot topics on the JRuby mailing lists lately. I’ve launched into a newly-refactored compiler that’s showing great performance gains. Many of us have discussed how to speed method dispatch and finally push interpreted-mode performance up to or beyond Ruby’s speed. And we’ve started to test and track Rails 1.2, while continuing to resolve remaining issues running Rails 1.1.6.

Now there’s a lot of work to do, but we’ve seen steady, continuous growth among JRuby contributors. Just in the past week we’ve had a number of new names on the mailing lists, we’ve added a new committer (Nick Sieger), and we’ve seen patches pouring in for more and more bugs. Things are going great.

Ola Bini: I was very happy about the last release. It fulfilled the goals I had set for it, which was to get OpenSSL and complete Java-backed YAML into it. Besides that, we also got seriously many bugs fixed in just a few months. Since I have a tendency to plan mostly for the next release, what I want to see in 0.9.3 is support for Sandbox, all those strange block scope bugs that surface in Rails gone, our load times improved (by refactoring the LoadService code), and finalizers finally working.

The Sandbox stuff is mostly done, and I also hacked a Generator that is so much faster than MRI that we come out faster, all in all, in a test case with generators.

Thomas Enebo: Largely, I think three goals are important: 1. Support Rails well enough where people do not need to ask us if it is ready for prime time; 2. Round out java integration support to do what most people expect it to do; 3. Make the runtime ‘fast’ enough. These three goals existed before JavaPolis, so I do not feel much has changed goal-wise.

How much closer have you come to achieving them? What is your perception of delta in growth in the JRuby community and acceptance of JRuby as a viable alternative to MRI?

Ola Bini: What I like about the last few months - since RubyConf - is that it really feels like JRuby and the other implementations will actually be viable alternatives and that there is something really useful going on. With Java open source, one of the major roadblocks for adoption in certain circumstances has all but disappeared. The contributions we have gotten is mostly visible in how many bug reports we get. That is really great, because that makes it that much easier to fix things. So I would say that the future looks brighter than ever.

Thomas Enebo: If you look at the amount of time between releases then you get a better idea of how much development has sped up. The time between 0.9.1 and 0.9.2 was a little under two months. This is the shortest development cycle to date and it seemed like we got so much done. Sun hiring us obviously had something to do with this, but also our community involvement is at an all time high. We get so many emails, bug reports, patches, tests, ideas, and enthusiasm coming in from the JRuby community. The community impact on JRuby is huge.

I think acceptance of JRuby as a Ruby interpreter is certain. Compatibility keeps improving, we keep getting faster, and we also offer integration with Java. If you look at the trend of how often JRuby is mentioned in blogs or the volume of email on our mailing lists, then I think you can get a picture as to whether people are willing to accept JRuby as a Ruby runtime.

Charles Nutter: Rails is probably the most visible measure of success for JRuby right now, and I’d say we’re able to run something like 75% of Rails 1.1.6 code and test cases. We’ve been using Rails’ own test suite as a yardstick for compatibility, with the idea that if we can run all the Rails test cases, we can say we support it. And that 75% is better than it might sound, since it’s the most heavily-used functions.

Now this might change, but we’re really hoping to claim full Rails support some time in February. We’re not sure if that will mean 90% of 1.1.6 test cases or 100% of 1.2 test cases, but we’re weighing options now. Finally having Rails support behind us will let us change focus toward outward to other applications and inward to improving JRuby internals and performance.

We’re also seeing daily gains in the performance area, with more to come. Since this past summer, we’ve managed to eliminate all the major performance bottlenecks seen when profiling. The only remaining area is the interpreter itself. My work on the compiler will eventually resolve that, and our work to improve the performance of method lookup and dispatch will help both interpreted and compiled execution. Everything’s moving very fast now. It’s going to be a great Spring for JRuby.

Probably the most intriguing change of the past month is the support from Aslak Hellesøy, creator of RSpec. Aslak has helped us get JRuby running RSpec extremely well, and we’re looking forward to the RSpec team using JRuby as part of their regression testing. I hope more Ruby app developers will take this same path, since their users are going be running JRuby more and more. Compatibility and regression testing for those apps should include JRuby just like it includes different Ruby versions and host operating systems.

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