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Sep: 19; 2007

RailsConf Europe Wednesday morning wrap-up - JRuby

By: Robert Dempsey | Tags:

Thank God for a continuous flow of coffee and multiple cafe’s on every block. I love Berlin! Things are as hectic today as they have been everyday.

The second half of this morning brought a talk on JRuby from Ola Bini, one of the JRuby development team. Ola’s presentation had a lot of material, so allow me to summarize:

What’s wrong with Ruby today?

Green threading
Partial Unicode support
Speed (slow)
Memory management, specifically the garbage collector
C language extensions
Politics (you want me to switch to what?)
Legacy (Java is everywhere)

What is JRuby?

Java implementation of Ruby
At version 1.0.1
Based on Ruby 1.8.5
6 core developers, open source, close to 40 contributors
Commercial backing from Sun and ThoughtWorks

What can JRuby do?

All ?��Ǩ?�pure Ruby?��Ǩ�� code works (with some caveats)
Rake and rubyGems run well
Rails works almost perfectly

What can’t JRuby do?

Deterministic threading
Continuations
Some file system operations
Forking, and other POSIX ilk

So, how does JRuby solve the stated problems with Ruby?

Native threading
Scaling across processors and cores
Concurrent execution
Thread scheduling
No politics - just another Java library

What challenges does JRuby face?

Performance of unit tests
It’s not “free” to run both JRuby and MRI (Matz’s interpreter)
Start-up time (especially with Rails)
JRuby regular expressions have different performance characteristics
YAML isn’t stable yet
High memory consumption (but still less than Mongrel)
Good replacement for RMagick is needed
Lack of documentation

It was a great session with a lot of information. Hopefully Ola will have his slides posted to the RailsConf Europe site.

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4 Responses to “RailsConf Europe Wednesday morning wrap-up - JRuby”

On September 19th, 2007 at 2:08 pm Gavin Stark said:

Thanks for providing such good summaries of what is going on at RailsConf Europe.

What exactly is meant by ‘It?��Ǩ�Ѣs not ?��Ǩ?�free?��Ǩ�� to run both JRuby and MRI (Matz?��Ǩ�Ѣs interpreter)’ “free” in what way? Did the JRuby team give any feedback on the next set of milestones and goal dates?

On September 19th, 2007 at 2:38 pm Robert Dempsey said:

Gavin,

Although Ola didn’t expand on this I believe he meant that there is overhead in running both on the same box. As for milestones and goals, nothing specific was told to us.

On September 20th, 2007 at 5:41 am Ola Bini said:

I could probably have been a little more explicit about that. What I meant is that it’s not free to develop an application that runs on both MRI and JRuby. There is a cost in supporting both platforms, since there are a few places where you need to code specific code for MRI or JRuby. Hope that clears it up.

On September 20th, 2007 at 1:36 pm Robert Dempsey said:

Thanks for the clarification Ola, and great presentation too!