Your JavaOne 2009 Ruby Guide

Here's a list of talks about Ruby or that mention/relate to Ruby at CommunityOne and JavaOne 2009. Some of these are about other languages, since I just did a dumb search for any mention of "ruby".

Add your suggestions in comments to help narrow down which talks people should go see.

CommunityOne:

S304128	Developing on the OpenSolaris™Operating System	David Miner, Sun Microsystems; Nicholas Solter, Sun Microsystems	Monday June 01 10:50 AM - 11:40 AM	Esplanade 305
S307894	Sun GlassFish™ Portfolio: Where Sun's Application Platform Is Going	Eduardo Pelegri-Llopart, Sun Microsystems, Inc.	Monday June 01 10:50 AM - 11:40 AM	Hall E 135
S304001	Pragmatic Identity 2.0: Invoking Identity Services with a Simplified REST/ROA Architecture	Pat Patterson, Sun Microsystems, Inc.; Daniel Raskin, Sun Microsystems, Inc.; Ron Ten-Hove, Sun Microsystems, Inc.	Monday June 01 11:50 AM - 12:40 PM	Gateway 102-103
S304141	Programming Languages and the Cloud	Ted Leung, Sun Microsystems, Inc.	Monday June 01 11:50 AM - 12:40 PM	Gateway 104
S304267	Beyond Impossible: How JRuby Has Evolved the Java™ Platform	Charles Nutter, Sun Microsystems, Inc.	Monday June 01 1:40 PM - 2:30 PM	Hall E 134
S304040	Social-Enable Your Web Apps with OpenSocial	Dave Johnson, IBM	Monday June 01 4:00 PM - 4:50 PM	Esplanade 300
S311290	JRuby Rails Workshop	Arun Gupta, Sun Microsystems, Inc.; Jacob Kessler, Sun Microsystems; Vivek Pandey, Sun Microsystems, Inc.; Nick Sieger, Sun Microsystems, Inc	Tuesday June 02 9:00 AM - 5:00 PM	Breakout Room 7
S311294	Cloud Computing and Storage in Practice	Tim Bray, Sun Microsystems, Inc.; Chris Kutler, Sun Microsystems, Inc.	Wednesday June 03 1:30 PM - 5:00 PM	Breakout Room 2

JavaOne:

PAN-5348	Script Bowl 2009: A Scripting Languages Shootout	Panel Session	Roberto Chinnici, Sun Microsystems, Inc.; Thomas Enebo, Sun Microsystems, Inc. ; Rich Hickey, Clojure;Guillaume Laforge, SpringSource; Raghavan Srinivas, Self; Dick Wall , Google; Frank Wierzbicki, Sun Microsystems, Inc.	Tuesday June 02 10:50 AM - 11:50 AM	Gateway 104
TS-4164	Clojure: Dynamic Functional Programming for the JVM™ Machine	Technical Session	Rich Hickey, Clojure	Tuesday June 02 12:10 PM - 1:10 PM	Hall E 133
TS-4487	The Feel of Scala	Technical Session	Bill Venners, Artima, Inc.	Tuesday June 02 3:20 PM - 4:20 PM	Gateway 104
TS-5015	Welcome to Ruby	Technical Session	Yehuda Katz, Engine Yard	Tuesday June 02 4:40 PM - 5:40 PM	Gateway 104
TS-5216	Toward a Renaissance VM	Technical Session	Brian Goetz, Sun Microsystems, Inc.; John Rose, Sun Microsystems	Tuesday June 02 6:00 PM - 7:00 PM	Hall E 133
BOF-4434	Hacking JRuby	BOF	Ola Bini, ThoughtWorks	Tuesday June 02 8:30 PM - 9:20 PM	Gateway 104
BOF-5058	JRuby Experiences in the Real World	BOF	Logan Barnett, Happy Camper Studios; David Koontz, JumpBox	Tuesday June 02 9:30 PM - 10:20 PM	Gateway 104
TS-5413	JRuby on Rails in Production: Lessons Learned from Operating a Live, Real-World Site	Technical Session	Nick Sieger, Sun Microsystems, Inc	Wednesday June 03 11:05 AM - 12:05 PM	Gateway 104
TS-4921	Dynamic Languages Powered by GlassFish™ Application Server v3	Technical Session	Jacob Kessler, Sun Microsystems; Vivek Pandey, Sun Microsystems, Inc.	Wednesday June 03 11:05 AM - 12:05 PM	Hall E 133
TS-4955	Comparing Groovy and JRuby	Technical Session	Neal Ford, ThoughtWorks Inc.	Wednesday June 03 2:50 PM - 3:50 PM	Gateway 104
BOF-4682	Performance Comparisons of Dynamic Languages on the Java™ Virtual Machine	BOF	Michael Galpin, eBay	Wednesday June 03 6:45 PM - 7:35 PM	Esplanade 300
TS-5385	Alternative Languages on the JVM™ Machine	Technical Session	Cliff Click, Azul Systems	Thursday June 04 9:30 AM - 10:30 AM	Gateway 104
TS-4012	Pragmatic Identity 2.0: Simple, Open, Identity Services Using REST	Technical Session	Pat Patterson, Sun Microsystems, Inc.; Ron Ten-Hove, Sun Microsystems, Inc.	Thursday June 04 10:50 AM - 11:50 AM	Esplanade 307-310
TS-4961	"Design Patterns" for Dynamic Languages on the JVM™ Machine	Technical Session	Neal Ford, ThoughtWorks Inc.	Thursday June 04 10:50 AM - 11:50 AM	Gateway 104
TS-5354	Exploiting Concurrency with Dynamic Languages	Technical Session	Tobias Ivarsson, Neo Technology	Thursday June 04 1:30 PM - 2:30 PM	Gateway 104
TS-5033	Scripting Java™ Technology with JRuby	Technical Session	Thomas Enebo, Sun Microsystems, Inc. ; Charles Nutter, Sun Microsystems, Inc.	Thursday June 04 2:50 PM - 3:50 PM	Gateway 104
TS-3955	Monkeybars: Tools-Enabled Swing Development with JRuby	Technical Session	Logan Barnett, Happy Camper Studios; David Koontz, JumpBox	Friday June 05 12:10 PM - 1:10 PM	Esplanade 302

BiteScript 0.0.2 Scripting Examples

I just released BiteScript 0.0.2, which mainly fixes some issues defining packages and non-public classes.

BiteScript is basically just a simple DSL for generating JVM bytecode. I use it in Duby and now in the "ruby2java" compiler we'll be using to turn Ruby classes into Java classes.

I've blogged about BiteScript here before, but I realized today I never posted any simple "hello world" examples. So here's a few of them, all using the command-line "scripting" mode.

First, the simplest version:

main do
  ldc "Hello, world!"
  aprintln
  returnvoid
end

Obviously this is using a predefined "aprintln" macro, since there's no "aprintln" opcode on the JVM. Here's a longer version that shows how a macro would be defined, and accepts one argument

import java.lang.System
import java.io.PrintStream

macro :aprintln do
  getstatic System, :out, PrintStream
  swap
  invokevirtual PrintStream, println, [Object]
end

macro :aprint do
  getstatic System, :out, PrintStream
  swap
  invokevirtual PrintStream, print, [Object]
end

main do
  ldc "Hello, "
  aprint
  aload 0
  aaload 0
  aprintln
  returnvoid
end

And of course this is just Ruby code, so you can just use Ruby to alter the generation of code:

main do
  5.times do
    ldc "Wow!"
    aprintln
  end
  returnvoid
end

These "BiteScripts" can all be either run with the "bite" command or compiled with the "bitec" command:

$ bite examples/using_ruby.bs 
Wow!
Wow!
Wow!
Wow!
Wow!

$ bitec examples/using_ruby.bs 

$ javap -c examples/using_ruby
Compiled from "examples.using_ruby.bs"
public class examples.using_ruby extends java.lang.Object{
public static void main(java.lang.String[]);
  Code:
   0: ldc #9; //String Wow!
   2: getstatic #15; //Field java/lang/System.out:Ljava/io/PrintStream;
   5: swap
   6: invokevirtual #21; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   9: ldc #9; //String Wow!
   11: getstatic #15; //Field java/lang/System.out:Ljava/io/PrintStream;
   14: swap
   15: invokevirtual #21; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   18: ldc #9; //String Wow!
   20: getstatic #15; //Field java/lang/System.out:Ljava/io/PrintStream;
   23: swap
   24: invokevirtual #21; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   27: ldc #9; //String Wow!
   29: getstatic #15; //Field java/lang/System.out:Ljava/io/PrintStream;
   32: swap
   33: invokevirtual #21; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   36: ldc #9; //String Wow!
   38: getstatic #15; //Field java/lang/System.out:Ljava/io/PrintStream;
   41: swap
   42: invokevirtual #21; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V
   45: return

}

This last example shows the resulting JVM bytecode as well.

Future plans for BiteScript include making it have better error detection (right now it just falls back on the JVM bytecode verifier, which is not the most descriptive thing in the world) and improving the API to more easily handle all the various combinations of class, field, and method modifiers. I'd also like to make it detect if you're doing bad things to the stack to save you the hassle of interpreting verification errors that may not happen until runtime.

Anyway, give it a try and feel free to contribute; the code is all Ruby, wrapping the ASM bytecode library, so anyone that knows Ruby can tweak it. The project page and wiki are hosted at Kenai.com: http://kenai.com/projects/jvmscript

And if you're not up on the JVM or JVM bytecodes, the JVM Specification is an easy-to-read complete reference for code targeting the JVM, and here is my favorite JVM opcode quickref.

Help JRuby by Fixing RubySpecs

A number of you have asked how you can help JRuby development. Well there's actually an easy way: fix RubySpec failures.

You may have noticed we periodically update our RubySpec "stable" revision number, and usually have to file a few bugs. This isn't because we don't want to fix those issues...on the contrary, we would love to fix them. We just don't have enough manpower, and there's usually harder issues we need to tackle first.

But most of the failures are easy to fix, and a lot of JRuby newcomers have gotten their feet wet fixing them. So here's a short guide on how to run the specs and fix them quickly.

1. Get a JRuby working copy and build it

This is as simple as 'git clone git://github.com/jruby/jruby.git', then 'cd jruby' and 'ant'. You'll need Apache Ant 1.7 and Java 5/1.5 or higher (grab "Java SE Development Kit" from the Java SE downloads page.

2. Run the CI spec run

We have a clean spec run that should be clean for you before you start. Just run "ant spec-short" and it will pull the mspec and rubyspec repositories, roll them to the stable versions, and run all known good specs. Now you're ready to investigate specific failures.

3. Run specific spec files with bugs reported

You can look in Jira under the "RubySpec" category, or look under spec/tags/ruby for "tag" files listing failing specs and Jira bug numbers. Once you find something you'd like to investigate, run that spec file using "bin/jruby spec/mspec/bin/mspec <path/to/spec/file>". For example to set the Range#initialize failures I just reported, run "bin/jruby spec/mspec/bin/mspec spec/ruby/core/range/initialize_spec.rb".

Now you can proceed to fixing it.

4. Identify where the problem is.

Most of the core classes are pretty easy to locate. Any classes in the "core" specs will have a Java class named Ruby, like RubyArray, RubyRange, and so on. They're generally located in src/org/jruby. If you know any Java, these files are pretty easy to follow, and we're standing by on IRC or on the mailing list to hold your hand at the start.

5. Create a patch and submit it to the bug

Once you have a working fix, you can go ahead create a patch, either with "git diff > somefile.patch" or by committing it to your local repository and using "git format-patch -1" to create a formatted patch for the topmost commit. Some git-fu may be necessary, so I usually just use "git diff".

That's all there is to it! You'll be a JRuby contributor in no time!

fork and exec on the JVM? JRuby to the Rescue!

Today David R. MacIver pinged me in #scala and asked "headius: Presumably you guys have spent quite a lot of time trying to make things like system("vim") work correctly in JRuby and failing? i.e. I'm probably wasting my time to attempt similar?"

My first answer was "yes", since there's no direct way to exec a program like vim (which wants a real terminal) and have it work on the JVM. The JVM's process launching gives the newly-spawned processes the child side of piped streams, which you then have to manually pump (which is what we do in JRuby's system, backtick, and exec methods). Under these circumstances, vim may start up, but it's certainly not functional.

But then I got to thinking...if you were doing this in C, you'd fork+exec and all would be happy. But we can't fork+exec on the JVM..OR CAN WE?

As you should know by now, JRuby ships with FFI, a library that allows you to bind any arbitrary C function in Ruby code. So getting fork+exec to work was a simple matter of writing a little Ruby code:

require 'ffi'

module Exec
 extend FFI::Library

 attach_function :my_exec, :execl, [:string, :string, :varargs], :int
 attach_function :fork, [], :int
end

vim1 = '/usr/bin/vim'
vim2 = 'vim'
if Exec.fork == 0
 Exec.my_exec vim1, vim2, :pointer, nil
end

Process.waitall

Running that with JRuby (I tried master, David tried 1.3.0RC1, and 1.2.0 works too) brings up a full-screen vim session, just like you'd expect, and it all just works. No other JVM language can do this so quickly and easily.

We'll probably try to generalize this into an optional library JRubyists can load (require 'jruby/real_exec' or similar) and perhaps add fork and exec to jna-posix so that the other JVM languages can have sweet, sweet process launching too.

JRuby rocks.

Update: The biggest problem with using fork+exec in this way is that you can't guarantee *nothing* happens between the fork call and the exec call. If, for example, the JVM decides to GC or move memory around, you can have a fatal crash at the JVM process level. Because of that, I don't recommend using fork + exec via FFI in JRuby, even though it's pretty cool.

However, since this post I've learned of the "posix_spawn" function available on most Unix variants. It's basically fork + exec in a single function, plus most of the typical security and IO tweaks you might do after forking and before execing. It's definitely my recommended alternative to fork+exec for JRuby, and to make that easier I've bundled it up as the "spoon" gem (gem install spoon) which provides spawn and spawnp to JRuby users directly. Here's an example session using Spoon to launch JRuby as a daemon. If you just need fork+exec on the JVM, posix_spawn or the Spoon gem are the best way to do it.

JRuby Nailgun Support in 1.3.0

I've merged changes into master (to be 1.3 soon) that should make Nailgun easier to use. And 1.3 will be the first release to include all NG stuff in the binary dist.

• jruby --ng-server starts up a server. You can manage it however you like
• jruby --ng uses the Nailgun client instead of launching a new JVM for the command you run. You'll just need to run make in tool/nailgun to build the ng executable (already built for you on Windows).

Future improvements will include having --ng start up the server for you if you haven't started it, passing signals through (don't expect signals to work at all right now), better management of threads and commands, and so on. But it's a good start, and people can try to play with it and report issues more easily now.

Heres a sample session:

~/projects/jruby ➔ cd tool/nailgun/ ; make ; cd -
Building ng client.  To build a Windows binary, type 'make ng.exe'
gcc -Wall -pedantic -s -O3 -o ng src/c/ng.c
ld warning: option -s is obsolete and being ignored
/Users/headius/projects/jruby

~/projects/jruby ➔ jruby --ng-server
NGServer started on all interfaces, port 2113.
^Z
[1]+  Stopped                 jruby --ng-server

~/projects/jruby ➔ bg
[1]+ jruby --ng-server &

~/projects/jruby ➔ jruby --ng -e "puts 1"
1

~/projects/jruby ➔ time jruby -e "puts 1"
1

real    0m0.609s
user    0m0.482s
sys    0m0.119s

~/projects/jruby ➔ time jruby --ng -e "puts 1"
1

real    0m0.073s
user    0m0.010s
sys    0m0.018s

Update: For those not familiar, "NailGun is a client, protocol, and server for running Java programs from the command line without incurring the JVM startup overhead. Programs run in the server (implemented in java), triggered by the client (written in C), which handles all I/O."

Update 2: It's been brought to my attention that we no longer ship a pre-configured Makefile for the ng client, so your build command line should actually look like:

~/projects/jruby ➔ cd tool/nailgun/ ; ./configure ; make ; cd -

Alternatively, you can run "ant build-ng" in the JRuby root, which will do largely the same thing for you using Ant.