1. JRuby
State of the Art!
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2. The JRuby Guys Tom Enebo and Charles Oliver Nutter
tom_enebo and headius on Twitter
4-6 years as JRuby devs
2.5 years at Sun Microsystems
12+ years as Java devs
Working from home (Minneapolis area)

3. Basic Facts JRuby 1.2.0 or JRuby 1.3.0RC1 Ruby 1.8.6 or 1.9.1 compat
--1.9 flag to use 1.9 mode
Rubygems, Rake, Rspec preinstalled
Simple install
Download bin tarball
Unpack
Put bin/ dir in PATH

4. Why Ruby on JVM Best memory management Dynamic optimizations
Reliable native threads
Vast numbers of libraries
Interop with Java, Scala, Rhino (JS), Jython, …
Ubiquitous
Why not?

5. JRuby and the JVM AST (interpreter) App code Java calls JRuby Runtime
Parser
Ruby stdlib
Compiler
Core classes
(String, etc)
Precompiled
code
.class loading
Bytecode
Java calls

6. Performance JRuby compiles Ruby to JVM bytecode
JVM compiles bytecode to native
Native code is optimized, inlined
Fastest production-ready implementation

7. The Magic of Hotspot Vector v = new Vector(3); // Thread-safe list
....
reset(v); // Called many times
void reset(Vector v) {
for (int i = 0; i < v.size(); i++) {
v.set(i) = 0; }

8. Hotspot: Method inlining
Inline
void reset(Vector v) {
fast_guard(v) {
for (int I = 0; I < lock { arr.length }; i++) {
lock { arr[i] = 0; } }

9. Hotspot: Simple Optz Unroll Loop void reset(Vector v) {
fast_guard(v) {
lock { arr[0] = 0; }
lock { arr[1] = 0; }
lock { arr[2] = 0; } }

10. Hotspot: Lock Coarsening
Coarsen Locks
void reset(Vector v) {
fast_guard(v) {
lock {
arr[0] = 0;
arr[1] = 0;
arr[2] = 0; }

11. Hotspot: ArrayCopyStub
Contiguous Array replaced by Array Copy Stub
void reset(Vector v) {
fast_guard(v) {
lock {
arrayCopyStub(v, [0,0,0]) }

12. Future JVM Work “invokedynamic”
New features in Java 7 for dynamic languages
Fast dynamic calls...as fast as Java
JRuby support by June
Multi-language VM “Da Vinci Machine”
Optimized tail calls
Continuations
Fixnums, value types
Faster, faster, always faster!

13. Threading Only production-ready impl with real threads
Ruby threads 1:1 native threads
Scale across cores, no forks necessary
One JRuby server process for an entire site

14. Simple Rails App Simple 1 controller, 1 model, 1 view app
Send 1000 reqs with concurrency 10 (ab)
GlassFish v2

15. Better Deployment The GlassFish gem gem install glassfish
Run 'glassfish' in app dir
Fast HTTP serving + load balancing
One process per application
Apache, nginx: just use mod_proxy

16. Ruby 1.9 Support Probably 80-90% complete
IO, Enumerable, some encoding stuff missing
IRB works, RubyGems works
Lack of Rubyspecs for 1.9
Number one way you could help

17. FFI Foreign Function Interface Call C functions directly from Ruby
Portable, unlike extensions
Most extensions just wrap a library
Started in Rubinius
JRuby added support in 1.1.4
JRuby team: Ruby FFI gem
gem install ffi

18. require 'ffi'
module POSIX
extend FFI::Library
# not usually necessary since libc is always linked
ffi_lib 'c'
attach_function :getuid, :getuid, [], :uint
attach_function :getpid, :getpid, [], :uint
end
puts "Process #{POSIX.getpid}, user #{POSIX.getuid}"

19. Who Uses JRuby?

20. Making the connection Sun's Project Kenai
A web platform of best-of-breed integrated collaborative “services”
Source code management
Subversion, Git, Mercurial
Issue/bug tracking
Jira, Bugzilla
Discussions (mailing lists & forums)
Wiki, feeds and aggregators
Content management & publishing
Building the Web,
Using the Web
Sun's Project Kenai

21. Sun's Kenai on JRuby Rails picked: Quick Development
Rapid Changes based on Customer feedback
Sun does more than just Java (the language)
JRuby picked:
Fits Sun software stack better (Java, Glassfish)
Wanted to demonstrate how JRuby can scale

22. Game Designers Gravitor (http://tinyurl.com/gravitor) A “real” game!
JRuby for game logic
Java for graphics library
Packaged as Mac, Windows app
King Pong
Ruby wrapping JMonkeyEngine

23. Mission-Critical Apps
Oslo's Gardermoen Airport
Refueling service
JRuby wrapping SWT, touchscreen libraries
Completed user acceptance, in production soon

24. ThoughtWorks Mingle on JRuby
Agile Project Management and Team Collaboration Tool
Reasons for JRuby on Rails:
No Cross Platform SVN library for Ruby
Bundling of installation (installer)
Security (encrypting source code)
Memory profile
Avoiding process proliferation

25. Oracle Mix on JRuby Idea collaboration tool for customers/employees
JRuby on Rails:
Agile: 5 developers 6 weeks for all development
Concise: LOC: 2887, Test LOC: 3691
Needed to integrate in Oracles environment
Java, Oracle DB
Same group is now writing second application with JRuby on Rails

26. Trisano Open Source Infectious Disease Reporting System
Battling Swine Flu as we speak
JRuby on Rails reasons:
Ease of deployment
Every enterprise on the planet runs Java
Development team has a Java heritage
Roadmap for the project is extensive and they wanted the fall back language to be Java rather than C.

27. JRuby on Google App Engine
GAE deploys WAR files
Warbler + jruby-rack
DataMapper wrapper for BigTable
Automatic up/down scaling
JRuby includes fixes for GAE
Updates for related projects coming soon
Talk tomorrow at 11:45AM

28. JRuby on GAE Hackathon!
Fun Fun Fun!

29. Open Q/A Ask anything, we'll answer or demo
No question is too dumb/simple/obvious
Catch us later if we run out of time