Re-introduction to JRuby as presented to the Boulder Ruby group on October 30, 2012.

1. Nick Sieger
@nicksieger

3. (RE-)
INTRO

4. Ruby on
the JVM

5. Best of Ruby
and Java...
Together!

6. http://www.flickr.com/photos/texascooking/5864122096/

7. COMPAT
IBILITY

8. runs nearly all pure ruby code
runs 92% of rubyspec suite
runs ~30% of 1.9 test suite
(even more with 1.8 mode)

9. http://jruby.org/download
rvm install jruby
INSTALL gem install jruby-lint
$ jrlint

10. drawbacks

11. startup time
memory footprint
native code
no Kernel#fork

12. PERFOR
MANCE

13. GC.pauses =
“no thanks”

14. class Simple
attr_accessor :next
end
top = Simple.new
puts Benchmark.measure {
outer = 10
total = 100000
per = 100
outer.times do
total.times do
per.times { Simple.new }
s = Simple.new
top.next = s
top = s
end
end
}

15. Ruby 1.9.3 JRuby
8000
6000
4000
2000
0
GC count

16. Ruby 1.9.3 JRuby
10000
1000
100
10
1
GC count

17. 15
Ruby 1.9.3 JRuby
12
9
6
3
0
GC time %

18. Time per GC versus heap usage
300ms
Ruby 2.0.0 JRuby
225ms
150ms
75ms
0ms
188KB/29MB 27MB/127MB 199MB/238MB
Heap usage (MRI/JRuby)

19. REAL
THREADS

20. Ruby 1.9 Ruby 1.9
unthreaded threaded
JRuby JRuby
unthreaded threaded

21. sidekiq.org
What if 1 Sidekiq process could
do the work of 20 Resque or
DelayedJob processes?

22. COMPILER

23. Ruby application code
JVM bytecode Key
Native code
Ruby Ruby
Ruby code
code code
Ruby Ruby
JRuby JRuby JRuby
code code
Ruby
JVM JVM JRuby JVM JRuby
code
Full interpretation JRuby compiler HotSpot compiler
Time

24. BENCH
MARKS

25. Red-Black Tree
5
4
ruby 1.9.3p286
jruby 1.7.0 java 1.6.0_29
3
jruby 1.7.0 java 1.7.0_09
jruby 1.7.0 java 1.7.0_09-b05 +indy
2
1
0

26. Times Faster than Ruby 1.9.3
5
JRuby/Java 6 JRuby/Java 7+indy
4.226 4.32
3.75
3.66
3.44
2.5 2.658
1.914 1.806
1.25 1.538 1.565
1.346
0
base64 richards neural mandelbrot redblack

27. Java 7

28. Get JDK 7
(OSX too!)
java.oracle.com

29. INVOKE
DYNAMIC

30. experthuman.com/
programming-with-
nothing
Tom Stuart
@tomstuart

31. # lambda
-> x {
}

32. # call
p[x]

33. FIZZ
BUZZ

34. (1..100).each do |n|
if (n % 15).zero?
puts 'FizzBuzz'
elsif (n % 3).zero?
puts 'Fizz'
elsif (n % 5).zero?
puts 'Buzz'
else
puts n.to_s
end
end

35. fizzbuzz = -> k { -> f { -> f { -> x { f[-> y { x[x][y] }] }[-> x {
f[-> y { x[x][y] }] }] }[-> f { -> l { -> x { -> g { -> b { b }[-> p {
p[-> x { -> y { x } } ] }[l]][x][-> y { g[f[-> l { -> p { p[-> x { ->
y { y } } ] }[-> p { p[-> x { -> y { y } } ] }[l]] }[l]][x][g]][-> l {
-> p { p[-> x { -> y { x } } ] }[-> p { p[-> x { -> y { y } } ] }[l]]
}[l]][y] }] } } } }][k][-> x { -> y { -> f { f[x][y] } } }[-> x { -> y
{ x } }][-> x { -> y { x } }]][-> l { -> x { -> l { -> x { -> x { -> y
{ -> f { f[x][y] } } }[-> x { -> y { y } }][-> x { -> y { -> f {
f[x][y] } } }[x][l]] } }[l][f[x]] } }] } }[-> f { -> x { f[-> y {
x[x][y] }] }[-> x { f[-> y { x[x][y] }] }] }[-> f { -> m { -> n { -> b
{ b }[-> m { -> n { -> n { n[-> x { -> x { -> y { y } } }][-> x { -> y
{ x } }] }[-> m { -> n { n[-> n { -> f { -> x { n[-> g { -> h {
h[g[f]] } }][-> y { x }][-> y { y }] } } }][m] } }[m][n]] }
}[m][n]][-> x { -> l { -> x { -> x { -> y { -> f { f[x][y] } } }[-> x
{ -> y { y } }][-> x { -> y { -> f { f[x][y] } } }[x][l]] } }[f[-> n {
-> p { -> x { p[n[p][x]] } } }[m]][n]][m][x] }][-> x { -> y { -> f {
f[x][y] } } }[-> x { -> y { x } }][-> x { -> y { x } }]] } } }][-> p {
-> x { p[x] } }][-> p { -> x {p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[
p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[
p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[p[
p[p[p[p[p[p[p[p[p[p[x]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]} }]][-> n { -> b {
b }[-> n { n[-> x { -> x { -> y { y } } }][-> x { -> y { x } }] }[-> f
{ -> x { f[-> y { x[x][y] }] }[-> x { f[-> y { x[x][y] }] }] }[-> f {
-> m { -> n { -> b { b }[-> m { -> n { -> n { n[-> x { -> x { -> y { y
} } }][-> x { -> y { x } }] }[-> m { -> n { n[-> n { -> f { -> x {
n[-> g { -> h { h[g[f]] } }][-> y { x }][-> y { y }] } } }][m] }

36. METHOD
HANDLES

37. INVOKEDYNAMIC
[bootstrapMethod]
bootstrapMethod():
Call Site
CallSite (once)
target
Method
Handle

38. package java.lang.invoke;
public abstract class MethodHandle {
public final native Object invoke(Object... args)
throws Throwable;
}

39. LAMBDA
p[x]

40. methodHandle.invoke(x);

41. java.lang.invoke.
MethodHandles
arrayElementGetter arrayElementSetter
spreadInvoker exactInvoker invoker
explicitCastArguments permuteArguments
constant identity insertArguments
dropArguments dropArguments
filterArguments filterReturnValue
foldArguments guardWithTest
catchException throwException

42. String literal
Constant lookup
Other literals
Instance variables
Method invocation
Math operations

43. IT’S A JVM
WORLD

44. DRIVE JAVA
FROM RUBY

45. require 'java'
require 'rubygems'
require 'flying_saucer'
java_import org.xhtmlrenderer.pdf.ITextRenderer
document = <<-HTML
<html><body><h1>Hello Flying Saucer!</h1></body></html>
HTML
File.open("doc.pdf", "wb") do |out|
renderer = ITextRenderer.new
renderer.set_document_from_string document
renderer.layout
renderer.create_pdf out.to_outputstream
end
system("open doc.pdf")
jruby -S gem install flying_saucer to try this example.

46. $ jruby saucer.rb

47. DECORATE
JAVA OBJECTS
WITH JRUBY

48. module java::util::Iterator
include Enumerable
def each
while has_next
yield self.next
end
end
end

49. DRIVE RUBY
FROM JAVA
(org.jruby.embed)

50. import org.jruby.embed.ScriptingContainer;
public class EmbedJRuby {
public static void main(String[] args) {
ScriptingContainer container = new ScriptingContainer();
container.runScriptlet("puts 'Hello from Ruby'");
}
}
(defn -main
"Call JRuby!"
[& args]
(doto (org.jruby.embed.ScriptingContainer.)
(.runScriptlet "puts 'Hello from Ruby!'")))

51. JRuby +
Clojure

52. ;; examples.clj
(def hmap (hash-map "foo" "FOO"
"bar" "BAR"
"baz" "BAZ"))
(println hmap)
(println (get hmap "bar"))
(println (contains? hmap "foo"))

53. # ruby
Java::clojure.main.main(["./examples.clj"])

54. github.com/
daveray/
familiar

55. Familiar.with do
# clojure.core functions here
# ‘-’ replaced with ‘_’
# e.g. hash-map => hash_map
end

56. Familiar.with do
r = ref(nil)
begin
ref_set r, 'foo'
rescue
puts "no transaction! #{$!}"
end
dosync do
ref_set r, 'foo'
end
p deref(r)
end

57. j.mp/
clojure-
from-jruby

58. FUTURE

60. {,bugs,wiki,ci}
jruby.org

61. github.com/
jruby

62. Thanks!