Ruby & Duby on Google App Engine: A Comparison of JRuby and Duby for Building Apps

Ruby & Duby on
Google App Engine
John Woodell
Ryan Brown
Nov 17, 2009

2

Wednesday, November 18, 2009

Google App Engine
3


What is Google App Engine?
• A cloud-computing platform
• Run your web apps on Google’s infrastructure
• We provide the container and services (PaaS)
– Hardware, connectivity
– Operating system
– JVM
– Servlet container
– Software services

4


Key Features
• No need to install or maintain your own stack
• We do the scaling for you
• Use Google’s scalable services via standard APIs
• Charge only for actual usage
– Always free to get started
• Built-in application management console

5


App Engine Architecture
Incoming Requests

Load App Engine App Engine App Engine
Balancer Front End Front End Front End

AppServer AppServer AppServer

Other Google
AppServer Infrastructure

API Layer - Bigtable

- Google Accounts

- Memcache
App App App
- Image manipulation

6


Traditional Ruby App Server Strategy
• Load everything into memory, servers can sit idle
• The “big box” database strategy, will eventually hit a wall
• Ruby and C extensions, portability issues, fewer APIs
• Allocate and administer machines, manage load balancers

7


JRuby on App Engine Strategy
• Load only what you need for each new instance
• Distributed persistence layer... simple and scalable
• JRuby and Java, catch exceptions and use first-class APIs
• Only worry about your application code in the container

8


WhiteHouse.gov/openforquestions

9


Quotas and Billing
Resource Provided Free Additional Cost
CPU 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

10


JRuby on App Engine
11


Easy to Install

sudo gem install google-appengine

Everything you need installs as gems

12


Support for JRuby
• Can outperforms MRI in many cases
• Gem extensions written in Java (no more segfaults)
• A wealth of integration options available
• Already works on App Engine with supported APIs

13


Support for Sinatra Microframework
• No learning curve... a simple and elegant DSL
• Some data-driven apps don’t require MVC or ActionView
• No need to extract the components we can’t use
• New application instances can spin up quickly

14


Support for Rails3
• More modular, load only what you need for each request
• Intelligent gem management and deployment tools
• First-class integrations with “other” ORMs like DataMapper
• Better routing and Rack integration
• Better Javascript integration and options
• Rails conventions!

15


Support for DataMapper
• Data mapped in your model, auto-migrations or no migrations
• Text fields treated like associations, lazy-load by default
• Create concise queries without using method_missing
• Supports validations and legacy AR finders
• Already works with dm-appengine wrapper

16


Support for Servlet 2.5 Spec
• Everything you need in in the container
• JRuby-Rack dispatches to Rack
while providing access to servlet features
• Access to Google App Engine APIs for Java
via Ruby APIs that are feature compatible
• Our tools allow you to develop in the container
with the ability to integrate Java servlets

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

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Dev AppServer
• Customized Jetty server
• 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

19


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)

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Administration
• Admin Console
– Invite others to be developers
– Browse your datastore & manage indexes
– View access data & error logs
– Analyze traffic
– View the status of scheduled tasks
– Test new versions of your app

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Demo

run lambda { |env| [200, {}, 'Hello'] }

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Current Issues with JRuby on App Engine
• Several seconds to “spin-up” a new JRuby instance
• Some gems still need their extensions ported to Java
• Not an officially supported platform

23


Introducing

Duby


Duby has Ruby-inspired Syntax

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

puts fib 10


// Generated from examples/Test.duby

public class Test extends java.lang.Object {

public static void main(String[] argv) {
System.out.println(Test.fib(10));
}

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

}


Duby’s not Ruby
• Statically typed
• No Duby runtime
• Uses Java’s type system

27


A Simple Duby App
import javax.servlet.http.HttpServlet
import com.google.appengine.ext.duby.db.Model

class Post < Model
def initialize; end

property title, String
property body, Text
end

class DubyApp < HttpServlet
def_edb(list, 'com/ribrdb/list.dhtml')

def doGet(request, response)
@posts = Post.all.run
response.getWriter.write(list)
end

def doPost(request, response)
post = Post.new
post.title = request.getParameter('title')
post.body = Text.new(request.getParameter('body'))
post.save
doGet(request, response)
end
end

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A Simple Duby App

class Post < Model
def initialize; end

property body, Text
end Types
class DubyApp < HttpServlet inferred from parent
class
end

post = Post.new
post.save
end
end

29


A Simple Duby App

class Post < Model
def initialize; end

property body, Text
end
Plugins
class DubyApp < HttpServlet

end

post = Post.new
post.save
end
end

30


Duby Supports Plugins
Only form of metaprogramming (for now)

require 'erb'

Duby::AST.defmacro('def_edb') do |duby, fcall, p|
name = fcall.args_node.get(0).name
path = fcall.args_node.get(1).value
erb = ERB::Compiler.new(nil)
...
src = erb.compile(IO.read(path))
duby.eval(src, p, “(edb)”)
end


Duby Can Use erb Templates
<title>Posts</title>
<body>
<h1>All Posts:</h1>
<% for post in @posts %>
<h2><%= post.title %></h2>
<p><%= post.body.getValue %></p>
<% end %>
<hr>
<h1>New Post:</h1>
<form method=post>
Title: <input type=text name=title><br>
Body: <textarea name=body></textarea><br>
<input type=submit>
</form>
</body>


More to Come
• Open classes
• Mix ins
• Blocks
• More

33


Resources
• Ryan Brown, ribrdb@google.com
John Woodell, woodie@google.com
• Google App Engine for JRuby
– http://code.google.com/p/appengine-jruby/
• Google Group
– http://groups.google.com/group/appengine-jruby
• Blog: JRuby on App Engine Blog
– http://jruby-appengine.blogspot.com/

34


Ruby & Duby on Google App Engine: A Comparison of JRuby and Duby for Building Apps

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