Oscon 2010

Ruby on Mirah on App Engine
Run your apps on Google Servers,
with access to first-class Java APIs
John Woodell
Charles Nutter
July 22, 2010

2

Saturday, July 24, 2010

Google App Engine
3


Key Features
• No need to install or maintain your own stack
• Use Google scalable services via standard APIs
• Built-in application management console
• Pay-as-you-go, with free quota to get started

4


Key Limitations
• No native code
• No threads or sockets
• No writing to the filesystem
• No more than 30 seconds per request

5


Dev AppServer
• Local implementation of services
– LRU memcache
– Disk-backed datastore
– HttpClient-backed URLFetch
• Emulates the production environment
– Sandbox restrictions may be inconsistent,
so run tests on production servers as well

6


Deployment
• Your app lives at
– <app_id>.appspot.com, or
– Custom domain with Google Apps
• Deploying uploads
– Static files
– Resource files
– Other metadata (datastore indexes, cron jobs)
• Admin Console
– dashboards
– manage multiple versions
– view logs

7


Quotas and Billing
Resource Provided Free Additional Cost
CPU time 6.5 hours/day $0.10/hour

Bandwidth In 1GByte/day $0.10/GByte

Bandwidth Out 1GByte/day $0.12/GByte

Stored Data 1 GB $0.005/GB-day

Emails sent 2000/day to users $0.0001/email
50000/day to admins

8


App Engine Product Roadmap
• SSL for third-party domains
• Background servers capable of running for longer than 30s
• Ability to reserve instances to reduce application loading overhead
• Ability to select different availability vs. latency options for Datastore
• Support for mapping operations across datasets
• Datastore dump and restore facility
• Raise request/response size limits for some APIs
• Improved monitoring and alerting of application serving
• Support for Browser Push (Comet) communication
• Built-in support for OAuth & OpenID

9


JRuby on App Engine
10


Benefits of JRuby
• Outperforms MRI in many cases... 2x to 10x
• Gem extensions written in Java (no more segfaults)
• A wealth of integration options and first-class Java APIs
• Spin-up new instances quickly using Mirah/Java servlets

11


App Engine JRuby Milestones
• 2009-04-08 @olabini publishes blog post on YARBL
• 2009-04-09 @nicksieger publishes warbler demo
• 2009-05-06 RailsConf (sinatra & merb)
• 2009-11-02 0.0.5 bundler, precompilation & Duby preview
• 2009-11-20 RubyConf (Rails 3.0.pre & Duby App)
• 2009-12-27 @urekat publishes Rails 2.3.5 patches
• 2010-01-11 @codingforrent published rails/dm gem
• 2010-01-21 0.0.8 Rails 2.3.5 Primer for DM & TinyDS
• 2010-01-26 0.0.9 Mechanize and Hpricot demos
• 2010-02-27 0.0.10 ActionMailer, ImageService, jruby-openssl
• 2010-04-08 @azazeal blog post on taxster.gr (OpenID)
• 2010-06-09 0.0.14 JRuby 1.5.1 & app.yaml preview
12


Current Issues with JRuby on App Engine
• Several seconds to “spin-up” a new JRuby instance
• Some gems may need their extensions ported to Java
• Not officially supported , but you have all that you need

+
13


Install it Now

sudo gem install google-appengine

Everything you need installs as gems

14


App Engine Gems
• Development Gems
– appengine-sdk
– appengine-tools . . . dev_appserver.rb & appcfg.rb
• Runtime Gems
– appengine-rack . . . . jruby-jars & jruby-rack
– appengine-apis
• Related Gems
– dm-appengine
– rails_appengine
– rails_dm_datastore
– rails_tiny_ds

15


App Engine JRuby APIs
• AppEngine::Users
• AppEngine::Datastore
• AppEngine::Memcache
• AppEngine::Mail
• AppEngine::URLFetch
• AppEngine::Images
• AppEngine::Logger
• AppEngine::XMPP
• AppEngine::Labs::TaskQueue
• AppEngine::OAuth
• AppEngine::Blobstore

16


Mirah
Charles Nutter

17


Me
• Charles Oliver Nutter
• JRuby co-lead
• Ex-Java EE developer
• @headius
• headius@headius.com
• blog.headius.com

My Day Job

• JRuby and JRuby-related extensions
• JVM-based utilities and libraries (for JRuby?)
• Bytecode generation
• Mobile and embedded interests
• Narrow, “system”-level scope


My Problem

• I love Ruby
• I write Java all day for JRuby
• How can I write Ruby all day?


What If This...
public class Foo {
private int a;

public Foo(int a) {
this.a = a;
}

public void show() {
System.out.println(a);
}
}


...Could Be This
class Foo
def initialize(a)
@a = a
end

def show
puts @a
end
end


Mirah
class Foo
def initialize(a:int)
@a = a
end

def show
puts @a
end
end


Mirah

• A nicer way to write Java
• Ruby syntax with modiﬁcations
• Feels like Ruby
• Compiles to Java/JVM
• No runtime library


Features From Ruby
• Optional arguments ✓
• Internal iteration ✓
• Closures ✓
• Literals ✓
• String interpolation ✓
• Mixins, “open” classes (soon)

Ruby

puts “Hello, world!”


Mirah

puts “Hello, world!”


Ruby
public static __file__(Lruby/__dash_e__;Lorg/jruby/runtime/ThreadContext;Lorg/jruby/
runtime/builtin/IRubyObject;[Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/
Block;)Lorg/jruby/runtime/builtin/IRubyObject;
@Lorg/jruby/anno/JRubyMethod;(name="__file__", frame=true, required=0, optional=0,
rest=-2)
L0
LINENUMBER 1 L0
ALOAD 1
ICONST_0
INVOKESTATIC ruby/__dash_e__.setPosition (Lorg/jruby/runtime/ThreadContext;I)V
ALOAD 0
INVOKEVIRTUAL ruby/__dash_e__.getCallSite0 ()Lorg/jruby/runtime/CallSite;
ALOAD 1
ALOAD 2
ALOAD 2
ALOAD 0
ALOAD 1
GETFIELD org/jruby/runtime/ThreadContext.runtime : Lorg/jruby/Ruby;
INVOKEVIRTUAL ruby/__dash_e__.getString0 (Lorg/jruby/Ruby;)Lorg/jruby/RubyString;
INVOKEVIRTUAL org/jruby/runtime/CallSite.call (Lorg/jruby/runtime/ThreadContext;Lorg/
jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/
runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
ARETURN


Mirah

public static void main(java.lang.String[]);
Code:
0:
getstatic
#12; //Field java/lang/System.out:Ljava/
io/PrintStream;
3:
ldc
#14; //String Hello, world!
5:
invokevirtual
#20; //Method java/io/
PrintStream.println:(Ljava/lang/String;)V
8:
return


Mirah

// Generated from DashE
public class DashE extends java.lang.Object {
public static void main(java.lang.String[] argv) {
java.io.PrintStream temp$1 = java.lang.System.out;
temp$1.println("Hello, world!");
}
}


Ruby
def fib(a)
if a < 2
a
else
fib(a - 1) + fib(a - 2)
end
end


Mirah
def fib(a:int)
if a < 2
a
else
fib(a - 1) + fib(a - 2)
end
end


Ruby
public static method__0$RUBY$fib(Lruby/__dash_e__;Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/
IRubyObject;Lorg/jruby/runtime/Block;)Lorg/jruby/runtime/builtin/IRubyObject;
@Lorg/jruby/anno/JRubyMethod;(name="fib", frame=true, required=1, optional=0, rest=-1)
ALOAD 3
ASTORE 9
L0
LINENUMBER 1 L0
ALOAD 1
ICONST_0
INVOKESTATIC ruby/__dash_e__.setPosition (Lorg/jruby/runtime/ThreadContext;I)V
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 9
LDC 2
INVOKEVIRTUAL org/jruby/runtime/CallSite.call (Lorg/jruby/runtime/ThreadContext;Lorg/jruby/runtime/builtin/IRubyObject;Lorg/jruby/runtime/builtin/
IRubyObject;J)Lorg/jruby/runtime/builtin/IRubyObject;
INVOKEINTERFACE org/jruby/runtime/builtin/IRubyObject.isTrue ()Z
IFEQ L1
ALOAD 9
GOTO L2
L1
FRAME FULL [ruby/__dash_e__ org/jruby/runtime/ThreadContext org/jruby/runtime/builtin/IRubyObject org/jruby/runtime/builtin/IRubyObject org/jruby/runtime/Block
T T T T org/jruby/runtime/builtin/IRubyObject] []
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 2
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 9
LDC 1
IRubyObject;Lorg/jruby/runtime/builtin/IRubyObject;)Lorg/jruby/runtime/builtin/IRubyObject;
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 2
ALOAD 0
ALOAD 1
ALOAD 2
ALOAD 9
LDC 2
L2
FRAME SAME1 org/jruby/runtime/builtin/IRubyObject
ARETURN


Mirah
public static int fib(int);
Code:
0:
iload_0
1:
iconst_2
2:
if_icmplt
9
5:
iconst_0
6:
goto
10
9:
iconst_1
10:
ifeq
17
13:
iload_0
14:
goto
30
17:
iload_0
18:
iconst_1
19:
isub
20:
invokestatic
#10; //Method fib:(I)I
23:
iload_0
24:
iconst_2
25:
isub
26:
invokestatic
#10; //Method fib:(I)I
29:
iadd
30:
ireturn


Mirah
}
public static int fib(int a) {
return (a < 2) ? (a) : ((DashE.fib((a - 1)) +
DashE.fib((a - 2))));
}
}


Ruby

def foo(a = 1, b = 2)
puts a + b
end


Mirah

def foo(a:int = 1, b:int = 2)
puts a + b
end


Mirah
public static java.io.PrintStream foo(int a, int b) {
java.io.PrintStream temp$1 =
java.lang.System.out;
temp$1.println((a + b));
return temp$1;
}
public static java.io.PrintStream foo() {
return foo(1);
}
public static java.io.PrintStream foo(int a) {
return foo(a, 2);
}


Ruby

a = [5,4,3,2,1]
a.each do |x|
puts x
end


Mirah

a = [5,4,3,2,1]
a.each do |x|
puts x
end


Mirah
java.util.List a =
java.util.Collections.unmodifiableList(
java.util.Arrays.asList(1, 2, 3, 4, 5));
java.util.Iterator __xform_tmp_1 = a.iterator();
label1:
while (__xform_tmp_1.hasNext()) {
java.lang.Object x = __xform_tmp_1.next();
label2:
{
temp$3.println(x);
}
}
}
}


Ruby

t = Thread.new do
puts “in thread”
end


Mirah

t = Thread.new do
puts “in thread”
end


Mirah
DashE.__xform_tmp_1 $binding = new DashE.__xform_tmp_1();
$binding.x = "in thread";
java.lang.Thread t = new java.lang.Thread(new DashE.__xform_tmp_2($binding));
}
public static class __xform_tmp_1 extends java.lang.Object {
java.lang.String x;
}
public static class __xform_tmp_2 extends java.lang.Object implements
java.lang.Runnable {
private DashE.__xform_tmp_1 binding;
public __xform_tmp_2(DashE.__xform_tmp_1 binding) {
this.binding = binding;
}
public void run() {
DashE.__xform_tmp_1 $binding = this.binding;
temp$1.println($binding.x);
}
}
}


It’s Not Ruby

• Using Java’s libraries and type system
• No “eval”
• No runtime-mutable classes
• Ruby libraries will not work


But It Feels Like Ruby!

• Clean, lightweight syntax
• Iteration, closures
• Far less “ceremony” than Java
• Performance equivalent to Java


mirah.org


Rails & Mirah Demos
John Woodell

50


Benefits of Mirah on App Engine
• New instances always spin-up in about a second
• Dubious framework uses familiar Rails conventions
• Code in Java or Ruby when Mirah lacks features you require
• The generated Java source can be inspected at any time

53


Mirah apps should look familiar to Rubyists


Mirah apps can use ERb templates


The generated Java source can be inspected


The ERb is transformed into method calls


Your model definition is very concise


Code is generated based on properties you define


All the basic methods you need are generated


Resources
• Blog
– http://jruby-appengine.blogspot.com
• Code Site
– http://code.google.com/p/appengine-jruby

• Examples Apps
– http://rails-primer.appspot.com
– http://dubious-demo.appspot.com

• Mirah Projects
– http://github.com/headius/mirah
– http://github.com/mirah/dubious

61


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