This document provides an overview of JRuby, highlighting both advantages and disadvantages compared to Ruby implementations. Key points include: - JRuby runs Ruby code on the Java Virtual Machine (JVM), allowing access to Java libraries and tools while retaining Ruby syntax and semantics. - The memory footprint of JRuby applications is initially larger than CRuby due to object sizes, but memory usage over time can be smaller with JRuby's garbage collection. - Features like fork, continuations, and some extensions may be missing or disabled in JRuby. - JRuby provides multiple Ruby versions and allows running multiple Ruby applications in a single JVM process. - Performance benchmarks show JRuby can be competitive with

1. JRuby Jam
Charles Nutter & Nick Sieger
@headius @nicksieger

2. JRuby Overview
JRuby > Ruby + Java

4. What's Different?

5. The Bad

6. Memory Footprint

7. Memory Footprint
Base memory size is larger
(Footprint over time is smaller)

8. Memory Footprint
Objects are larger
(But instance var table is smaller)

9. Missing or Disabled
Features

10. Missing or Disabled
Features
No Kernel#fork

11. Missing or Disabled
Features
No continuations (callcc)
(except for specific forms)

12. Missing or Disabled
Features
ObjectSpace off by default
(-X+O to enable)

13. Missing or Disabled
Features
set_trace_func off by default
(--debug to enable)

14. C Extensions
Shipped in JRuby 1.6,
still considered experimental

15. The Good

16. Getting Started
Install a JVM
(depends on your OS)

17. Getting Started
rvm install jruby

19. Getting Started
Download from jruby.org

21. Ruby Itself

22. Ruby Itself
Ruby 1.8.7 and 1.9.2 in the box

24. Ruby Itself
Multi-VM support
(many apps in one process)

26. Ruby Itself
Solid across platforms

27. Ruby Itself
Solid across platforms
(Best Ruby on Windows?)

28. Ruby Itself
Solid across platforms
(Best Ruby on OpenVMS?)

29. Ruby Itself
Solid across platforms
(Best Ruby on zLinux?)

30. Java Virtual Machine
(JVM)

31. Java Virtual Machine
(JVM)
Java libraries like Swing
(or Scala, Groovy, Clojure, etc)

32. # Import Java packages
require 'java'
# Pull in some classes
java_import javax.swing.JFrame
java_import javax.swing.JButton
# create frame and button
frame = JFrame.new("Hello Swing")
button = JButton.new("Klick Me!")
button.add_action_listener do
button.text = "You klicked!"
end
# Add the button to the frame
frame.content_pane.add(button)
# Show frame
frame.default_close_operation =
JFrame::EXIT_ON_CLOSE
frame.pack
frame.visible = true

35. Java Virtual Machine
(JVM)
Tools like VisualVM

39. Java Virtual Machine
(JVM)
Concurrent threading

41. Java Virtual Machine
(JVM)
Best garbage collectors

42. Java Virtual Machine
(JVM)
Optimizing JIT compiler

43. Java Virtual Machine
(JVM)
New dynamic dispatch support
(invokedynamic)

44. Invokedynamic
What Java 7 Means for JRuby 1.7

45. Ruby = Method Calls
Lots and lots and lots and lots...

46. def foo
bar
end
def bar
baz foo bar baz
end
def baz
# ...
end

47. def foo
JRuby on Java 5/6
bar
end
def bar JRuby JRuby
baz foo call bar call baz
end logic logic
def baz
# ...
end
Kills many JVM optimizations

48. def foo
JRuby on Java 7
bar
X X
end
def bar JRuby JRuby
baz foo call bar call baz
end logic logic
def baz
# ...
end
Dynamic call logic built into JVM

49. def foo
JRuby on Java 7
bar
end
def bar
baz foo bar baz
end
def baz
# ...
end
Straight through dispatch path

50. def foo
JRuby on Java 7
bar
end
def bar
baz foo bar baz
end
def baz
# ...
end
Optimizations (like inlining) can happen!

51. Benchmarks!
You know you love them.

52. A “Better” fib bench
bench_fib_complex.rb 5 35

53. “Richards”
bench_richards.rb 1000000

54. Red/Black Tree
github.com/headius/redblack

55. Wait for it...
Benchmarks are benchmarks.
If you don’t like them, give us yours!

57. Deployment

58. Ruby servers WAR files Cloud
WEBrick GlassFish EY AppCloud
Trinidad Tomcat AppEngine
TorqueBox JBoss AWS EB
http://ey.io/webservers

59. torquebox.org/
$ torquebox deploy ~/src/sinatra/basic
$ torquebox run

60. Warbler
Rails in a .war file
INSTALL gem install warbler
github.com/jruby/warbler

61. $ cd ~/apps/recordstore

62. $ cd ~/apps/recordstore
$ warble executable war
rm -f recordstore.war
Creating recordstore.war

63. $ cd ~/apps/recordstore
$ warble executable war
rm -f recordstore.war
Creating recordstore.war
$ java -jar recordstore.war
<server starts on port 8080>

64. JRuby-Rack
Servlet => Rack conversion layer
Used by Warbler and Trinidad
github.com/jruby/jruby-rack

65. JRuby-Rack
JRuby-Rack Your
Servlet
servlet Rack Rails/Rack
container filter app

66. JRuby on AppCloud
EYSD, JRuby 1.6.x, Trinidad
docs.engineyard.com/appcloud-tech-stack.html

67. JRuby on AppCloud
Dashboard deploy
Add to Gemfile
gem 'trinidad'
Command-line deploy
$ gem install engineyard
$ cd ~/apps/recordstore
$ ey deploy

68. Tuning
Your application is special

69. JVM server compiler
Always run with --server

70. config.threadsafe!
1 runtime > pooled runtimes
Trinidad Warbler
trinidad --threadsafe config.webxml.jruby.max.runtimes = 1

71. Database pool
default is 5
threadsafe needs more connections
database.yml
production:
adapter: mysql
pool: 200

72. HTTP connection thread pool
# of open files limit
JVM max heap size (-Xmx___m)
JVM GC -XX:+UseConcMarkSweepGC -XX:+UseG1GC

73. Performance
JRuby vs. Passenger

74. Static Benchmark
EY AppCloud c1.medium
github.com/
nicksieger/redmine
MySQL
Passenger 3 JRuby 1.6.4
REE 2011.03 Trinidad 1.2.1

75. Request/reply scaling curve
90
80
jruby reply rate
70 passenger reply rate
Requests per second
60
50
40
30
20
10
0
10 20 30 40 50 60 70 80 90
Replies per second

76. Request/reply scaling curve
90
80
jruby reply rate
70 passenger reply rate
Requests per second
PS
60
50 OO did I mention
40 JRuby’s in
30 beta?
20
10
0
10 20 30 40 50 60 70 80 90
Replies per second

77. Passenger

78. JRuby

79. Catastrophic failure
Previous page
(no longer visible)

80. Passenger Memory

81. JRuby Memory

82. Performance
Takeaways

83. Speed-competitive
Will require warm-up
Faster with newer versions of Java

84. Memory efficient
at higher throughput
Threads lighter than processes

85. May need tuning
Guidelines and JVM tools
will help pinpoint configuration

86. JRuby T-Shirts!

87. Try JRuby on Engine Yard Cloud Today
500 compute hours for free
Full-featured production ready
environment
Start and stop your
environment as needed
No credit card required and
completely risk free

88. Engine Yard @ JavaOne!
Stop by our exhibition
booth
JRuby team office hours
Talks by JRuby team
Talk by Mike Piech and
Jacob Lehrbaum on the
value of PaaS

89. Q&A
We must have missed something