Clone TinyURL with 40 lines of Ruby code on Google AppEngine for Java
May 15th, 2009 by sausheong
Amidst the wretched events that happened at work recently, I forgot about an interesting development in running apps on a cloud. Google AppEngine finally released Java support on the AppEngine platform. For those uninitiated, AppEngine is Google’s cloud computing platform that allows developers to serve up applications on Google’s infrastructure. When it was first released in April 2008, the only language supported was Python. Python is a great language but doesn’t appeal to my inner Rubyist so it didn’t catch my attention. Until now that is.
While Java is no longer my language of choice nowadays, Ruby actually runs pretty well under JRuby with Java. And with the addition of the Java support for AppEngine, it became a lot more interesting. A few weeks back I wrote Snip, a TinyURL clone, in about 40 lines of Ruby code, and deployed it on Heroku. It seems like a good idea to take Snip out for a spin on the Google AppEngine for Java (GAE/J).
The first thing you need to do is to create an application on the GAE/J. Start by going to this URL - http://appengine.google.com/start and log in using a Google account. After logging in, create a new application following the instructions given on the screen. When you’re done you should have an application id. In this case, it is ’saush-snip’. We will be needing this application id in our configuration later. You will also need to enable Java for your GAE/J. At this point in time, GAE/J is still in beta and Google is only limiting the first 10,000 developers from enabling Java for GAE/J. Unfortunately if you don’t get Java enabled for your account, you won’t be able to try this out until it is fully released and available to all.
Once you have signed up and gotten an email approval for your GAE/J account, the first thing to do is to install JRuby, if you haven’t done so yet. Even if you have installed it previously you might want to install at least 1.3.0RC1 since some fixes were added into this release to make it run better under GAE/J. Run this:
$ git clone git://github.com/jruby/jruby.git
This will clone a copy of JRuby into your computer. Then go into the jruby folder that was just created and run this:
$ sudo ant && sudo ant jar-complete
This will install JRuby and create the jruby-complete.jar library that you will need in a while. Take note of this path to JRuby, you’ll need it in the subsequent commands. Assume that you just installed JRuby in ~/jruby, do a quick check to see if the install is ok:
$ ~/jruby/bin/jruby -v
If you installed version 1.3.0RC1 you should see something like this:
jruby 1.3.0RC1 (ruby 1.8.6p287) (2009-05-11 6586) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_07) [x86_64-java]
After installing JRuby, you’ll need to install all gems needed for this application. Remember that even if you have installed gems for your normal Ruby installation you’ll need to install it all over again for JRuby. For Snip, you need Sinatra and HAML, but you’ll also need Rake and Warbler, the JRuby war file packager.
$ ~/jruby/bin/jruby -S gem install rake sinatra haml warbler
Now that the basic JRuby and related gems are done, let’s look at the Snip code itself. One thing that is pretty obvious upfront when dealing with AppEngine is that it doesn’t have a relational database for persistence. Instead of a familiar RDBMS, we get a JDO interface or a DataStore API. How do we use it? As it turns out, we don’t need to do anything major. Ola Bini wrote a small wrapper around DataStore, called Bumble, to allow us to write data models just like we did with DataMapper. Well, almost.
Using Bumble is very much similar to DataMapper and ActiveRecord, so I didn’t have to change my code much. This is the DataMapper version of the Url model:
DataMapper.setup(:default, ENV['DATABASE_URL'] || 'mysql://root:root@localhost/snip') class Url include DataMapper::Resource property :id, Serial property :original, String, :length => 255 property :created_at, DateTime def snipped() self.id.to_s(36) end end
And this is the Bumble version of the Url model:
class Url include Bumble ds :original def snipped() self.key.to_s end end
I didn’t add in the time stamp for the Bumble version because I don’t really use it but as you can see there are quite a bit of similarities. I didn’t need to put in my own running serial id because it’s managed by the AppEngine. Also, instead of using the object id, I used the object’s key, which again is managed by the AppEngine. A key is a unique identifier of an entity across all apps belonging to the user. The key is created automatically by Bumble through the low-level DataStore Java APIs. Besides this, using the Url class is slightly different also. Instead of
@url = Url.first(:original => uri.to_s)
We use:
@url = Url.find(:original => uri.to_s)
Finally because we don’t use the id anymore and use the key instead, we don’t need to do the base 36 conversion so we let the AppEngine handle everything. Instead of:
get '/:snipped' do redirect Url[params[:snipped].to_i(36)].original end
We use:
get '/:snipped' do redirect Url.get(params[:snipped]).original end
This is the full source code:
%w(rubygems sinatra bumble uri).each { |lib| require lib}
get '/' do haml :index end
post '/' do
uri = URI::parse(params[:original])
raise "Invalid URL" unless uri.kind_of? URI::HTTP or uri.kind_of? URI::HTTPS
@url = Url.find(:original => uri.to_s)
@url = Url.create(:original => uri.to_s) if @url.nil?
haml :index
end
get '/:snipped' do redirect Url.get(params[:snipped]).original end
error do haml :index end
use_in_file_templates!
class Url
include Bumble
ds :original
def snipped() self.key.to_s end
end
__END__
@@ layout
!!! 1.1
%html
%head
%title Snip! on Google AppEngine
%link{:rel => 'stylesheet', :href => 'http://www.w3.org/StyleSheets/Core/Modernist', :type => 'text/css'}
= yield
@@ index
%h1.title Snip! on Google AppEngine
- unless @url.nil?
%code= @url.original
snipped to
%a{:href => env['HTTP_REFERER'] + @url.snipped}
= env['HTTP_REFERER'] + @url.snipped
#err.warning= env['sinatra.error']
%form{:method => 'post', :action => '/'}
Snip this:
%input{:type => 'text', :name => 'original', :size => '50'}
%input{:type => 'submit', :value => 'snip!'}
%small copyright ©
%a{:href => 'http://blog.saush.com'}
Chang Sau Sheong
%br
%a{:href => 'http://github.com/sausheong/snip-appengine'}
Full source code
The code is ready but here comes the packaging. GAE/J is a Java servlet environment, which means our app needs to be packaged into a war (Java Web ARchive). Fortunately instead of building up the war by hand we can use Warbler, the JRuby war packager. Before running Warbler, we need to have a couple of things. Firstly we need to build the warble configuration file:
$ mkdir config $ ~/jruby/bin/jruby -S warble config
We create a directory called config and get Warbler to copy a default configuration file to it. Replace the contents with this minimal setup. If you want to explore more, read warble.rb itself.
Warbler::Config.new do |config|
config.dirs = %w(lib public views)
config.includes = FileList["appengine-web.xml", "snip.rb", "config.ru", "bumble.rb"]
config.gems = ['sinatra', 'haml']
config.gem_dependencies = true
config.war_name = "saush-snip"
config.webxml.booter = :rack
config.webxml.jruby.init.serial = true
config.java_libs.reject! { |lib| lib =~ /jruby-complete/ }
end
Note that we don’t really need the public and view directories in Snip because everything is in a single file. The 2 other configuration files we will need are appengine-web.xml and config.ru. We also need to include the snip.rb and bumble.rb into the war file for deployment. To get bumble.rb, go to Ola Bini’s Bumble GitHub repository and get the file that is in the sub-folder (not the main one). The last line tells us not to include the jruby-complete.jar library in the lib folder when we run Warbler. I’ll explain this in a minute. Also note the war file is the application id of the application we created in the GAE admin console earlier on (saush-snip).
Next, create a lib folder. Go to the GAE/J download site and download the GAE/J Java library. It should be called something like appengine-api-1.0-sdk-1.2.0.jar. Copy that into the lib folder you’ve just created. We will also need the Java libraries in the lib folder. Normally for a JRuby deployment, Warbler will package it in, but Google has a 1,000 file limit which Ola Bini kindly pointed out. He also provided a script to split the JRuby library into 2 files. You can find the script here and when you run it, it should split jruby-complete.jar into 2 files named jruby-core-1.3.0RC1.jar and jruby-stdlib-1.3.0RC1.jar. You will also need JRuby-Rack but it’s included in Warbler and as you will see later, Warbler will copy it into the war when you run it. JRuby-Rack is an adapter for the Java servlet environment that allows Sinatra (or any Rack-based application) to run.
The next piece is appengine-web.xml. I used Ola Bini’s version as the base:
<appengine -web-app xmlns="http://appengine.google.com/ns/1.0">
<application>saush-snip</application>
<version>1</version>
<static -files />
<resource -files />
<sessions -enabled>false</sessions>
<system -properties>
<property name="jruby.management.enabled" value="false" />
<property name="os.arch" value="" />
<property name="jruby.compile.mode" value="JIT"/> <!-- JIT|FORCE|OFF -->
<property name="jruby.compile.fastest" value="true"/>
<property name="jruby.compile.frameless" value="true"/>
<property name="jruby.compile.positionless" value="true"/>
<property name="jruby.compile.threadless" value="false"/>
<property name="jruby.compile.fastops" value="false"/>
<property name="jruby.compile.fastcase" value="false"/>
<property name="jruby.compile.chainsize" value="500"/>
<property name="jruby.compile.lazyHandles" value="false"/>
<property name="jruby.compile.peephole" value="true"/>
<property name="jruby.rack.logging" value="stdout"/>
</system>
</appengine>
The list row in the property line sets logging to STDOUT, which is very useful for debugging. If you don’t set this, you might not be able to see any console output. Again, we need to set the application id that we got earlier on (saush-snip).
Finally we need a config.ru Rackup file to start the whole thing:
%w(rubygems sinatra snip).each { |lib| require lib}
root_dir = File.dirname(__FILE__)
set :environment, :production
set :root, root_dir
set :app_file, File.join(root_dir, 'snip.rb')
disable :run
run Sinatra::Application
You can of course also find all these things in the Snip-AppEngine repository at git://github.com/sausheong/snip-appengine.git. However it is so much more fun to do it step by step right?
Now that we have all the pieces let’s package our files for deployment. First we need to generate the exploded war file:
$ ~/jruby/bin/jruby -S warble
You should see output like this:
mkdir -p tmp/war/WEB-INF/gems/specifications cp /Users/saush/jruby/lib/ruby/gems/1.8/specifications/sinatra-0.9.1.1.gemspec tmp/war/WEB-INF/gems/specifications/sinatra-0.9.1.1.gemspec mkdir -p tmp/war/WEB-INF/gems/gems JRuby limited openssl loaded. gem install jruby-openssl for full support. http://wiki.jruby.org/wiki/JRuby_Builtin_OpenSSL cp /Users/saush/jruby/lib/ruby/gems/1.8/specifications/rack-0.9.1.gemspec tmp/war/WEB-INF/gems/specifications/rack-0.9.1.gemspec cp /Users/saush/jruby/lib/ruby/gems/1.8/specifications/haml-2.0.9.gemspec tmp/war/WEB-INF/gems/specifications/haml-2.0.9.gemspec mkdir -p tmp/war/WEB-INF/lib mkdir -p tmp/war/WEB-INF/public mkdir -p tmp/war/WEB-INF/views cp lib/appengine-api-1.0-sdk-1.2.0.jar tmp/war/WEB-INF/lib/appengine-api-1.0-sdk-1.2.0.jar cp lib/jruby-core-1.3.0RC1.jar tmp/war/WEB-INF/lib/jruby-core-1.3.0RC1.jar cp lib/jruby-stdlib-1.3.0RC1.jar tmp/war/WEB-INF/lib/jruby-stdlib-1.3.0RC1.jar cp appengine-web.xml tmp/war/WEB-INF/appengine-web.xml cp snip.rb tmp/war/WEB-INF/snip.rb cp config.ru tmp/war/WEB-INF/config.ru cp bumble.rb tmp/war/WEB-INF/bumble.rb cp /Users/saush/.gem/jruby/1.8/gems/warbler-0.9.13/lib/jruby-rack-0.9.4.jar tmp/war/WEB-INF/lib/jruby-rack-0.9.4.jar cp /Users/saush/.gem/jruby/1.8/gems/warbler-0.9.13/lib/jruby-rack-0.9.4.jar tmp/war/WEB-INF/lib/jruby-rack-0.9.4.jar mkdir -p tmp/war/WEB-INF jar cf saush-snip.war -C tmp/war .
You will also get a saush-snip.war file and a bunch of files under the tmp folder, which is really just the war file exploded. We won’t need the war file (saush-snip.war) itself for deployment, only the tmp directory. Before doing the deployment, we need to make a minor adjustment to the tmp/war/WEB-INF/gems/gems/sinatra-0.9.1.1/lib/sinatra.rb file. Somehow the line ‘use_in_file_templates!’ gives an error when deploying to the GAE/J so comment it out.
That’s it! We are ready for the deployment. To deploy run this command:
$ ~/appengine-java-sdk-1.2.0/bin/appcfg.sh --email= --passin update tmp/war/
You should see output like this:
Reading application configuration data... 2009-05-15 19:51:38.916::INFO: Logging to STDERR via org.mortbay.log.StdErrLog Beginning server interaction for saush-snip... Password for : 0% Creating staging directory 5% Scanning for jsp files. 20% Scanning files on local disk. 25% Scanned 250 files. 28% Initiating update. 31% Cloning 340 application files. 33% Cloned 100 files. 34% Cloned 200 files. 35% Cloned 300 files. 40% Uploading 0 files. 90% Deploying new version. 95% Will check again in 1 seconds 98% Will check again in 2 seconds 99% Closing update: new version is ready to start serving. 99% Uploading index definitions. Update complete. Success. Cleaning up temporary files...
Now go to http://saush-snip.appspot.com and you should be able to see the new deployment of Snip on the Google AppEngine for Java.
A few other tutorials on the Internet also describe how to deploy Sinatra or Rails-based apps on GAE/J, amongst which Samuel Goebert’s tutorial and Ola Bini’s stand out the most.
A few thoughts on comparing Heroku and GAE/J since I’ve deployed on both of them now. Heroku is definitely the easier platform to deploy, with a just few simple steps compared to the hoops I had to jump for GAE/J. Heroku also has the arguably more familiar persistence mechanism as it uses the familiar RDBMS (postgresql) compared to Google’s DataStore implementation, which today only has Ola Bini’s Bumble implementation compared to the established ActiveRecord, DataMpper and Sequel ORMs. In addition, Google’s implementation has many limitations, some harder to understand than others, which forces applications to suit this platform rather than having the platform really service the application.
On the other hand, Google’s set of tools in its console is really impressive, with graphs of usage, data and log viewers. Google AppEngine also has memcached, url fetcher, integration with Google accounts, sending out mails and hosts of other helper services. Also, Google’s brand name does add some weight when you throw in more mission critical projects though Heroku, backed by Amazon’s EC2 services is no push-over. As for costs, until large deployments emerge it is hard to say which is the better deal, also it really depends highly on usage patterns.
So are they evenly balanced out? Not for me at least. For now I would still favor Heroku over GAE/J because Heroku is more friendly to Ruby developers. But who knows? It’s exciting times for Rubyists.
Packt Author Award 2009 - Vote for my book!
May 5th, 2009 by sausheong
It’s a year to the month since I published my first book - Ruby on Rails Web Mashup Projects. I didn’t even realise it — time really does fly. Just got a mail from my publisher announcing that they’re having an award for the best author of the year. If you’re one of my readers, or if you enjoyed reading this blog please consider voting for my book.
Here’s the link - http://authors.packtpub.com/content/packt-author-award-2009. Just click on Vote Now! and select Ruby on Rails Web Mashup Projects in the list of books to vote for. Thanks!
Third party user authentication with Ruby in a just few lines of code
April 25th, 2009 by sausheong
Some time ago (8 years to be exact) when I was still chest-deep in Java and working in elipva, I wrote Tapestry, a centralized user management system and also an article in Javaworld describing it. That particular project is long gone (it got merged into elipva’s Zephyr product and disappeared as a standalone system) but the problems I wrote about are really quite universal.
To summarize, the main problem that Tapestry tried to solve was that software applications that serve more than 1 user at a time usually require its users to sign in. To do that, most of the time, we create a user management module. Within this user management module we need to provide these 2 major services:
- Authentication — you are really who you say you are
- Access control — you have permission to do what you want to do with something
As you can imagine, authentication is usually simpler than access control. Tapestry’s approach was to externalize these services into a configurable standalone system that provides both services. While I never really completed Tapestry, there are many third-party providers of these services in the market now. In this blog post I will talk about authentication and explain some ways to easily integrate your Ruby application with these third-party authentication providers.
But before that, some background. In the open era, 2 different open technologies have surfaced to solve the the issues of authentication and access control separately. OpenID is a popular digital identity used for authentication, originally developed for LiveJournal in 2005. It’s supported by many large companies including Yahoo, Google, PayPal, IBM, Microsoft and so on. As of Nov 2008, there are over 500 million OpenIDs on the Internet and about 27,000 sites have integrated it. OAuth is a newer protocol used for access control, first drafted in 2007. It allows a user to grant access to information on one site (provider) to another site (consumer) without sharing his identity. OAuth is strongly supported by Google and Yahoo, and is used also in Twitter.
At the same time, many larger organizations started to tout their proprietary own authentication and access control mechanism. Microsoft started its Passport service in 1999 and received much criticism along the way (later it changed its name to Windows Live ID). Soon after, in September 2001, the Liberty Alliance was started by Sun Microsystems, Oracle, Novell and so on (which many considered a counter to Passport) to do federated identity management. As mentioned, Google is one of the initial and strong supporter of OAuth but it also offers an older AuthSub web authentication and ClientLogin client authentication APIs while being an OpenID provider (it calls its OpenID service Federated Login). Yahoo started supporting OAuth officially in 2008, in addition to its older BBAuth APIs and is also an OpenID provider. Facebook joined the race in 2008 with Facebook Connect, which does authentication as well as share Facebook information. MySpace also came in with their platform in 2008, originally called Data Availability, which quickly became MySpaceID. In April 2009, Twitter started offering ‘Sign In with Twitter‘, which true to its name, allow users to sign in with their Twitter accounts. In addition to that Twitter uses HTTP basic authentication to protect its resources, and also recently announced support for OAuth.
As you can see there’re really lots of players in the market. RPXNow, which I blogged about previously, took advantage of these offerings and came up with a unified and simplified set of APIs to allow authentication with Yahoo, Google, Windows Live ID, Facebook, AOL, MySpace and various OpenID providers.
Looking from another perspective, there are 2 types of third party authentication APIs:
- Web authentication for web applications
- Client authentication for desktop or mobile client applications
The main difference between these 2 types of authentication is that web authentication can redirect the user to provider’s site for him to enter his username and password, then returns to the calling web application, usually with a success or failure token. Client authentication (usually) cannot do this, and would require the application to capture the username and password, which is sent by the client application to the provider. Obviously from a security point of view, web authentication is more secure and re-assuring to users since the user never needs to pass the username and password to the application at all.
Let’s jump into some code now. I will give 2 examples of both web authentication and client authentication each. You can find all the code here at git://github.com/sausheong/auth.gi
Let’s start with RPX because that’s the easiest. Using RPX is probably the easiest way to do third party web authentication with a large number of different providers. You can either use its provided interfaces (either embedded or pop-up Javascript) or you can call its simple API to authenticate your web application. Here’s a simple Sinatra example.
There are just 2 files. rpx_auth.html is in the public folder:
<form method="POST" action="https://chirp-saush.rpxnow.com/openid/start?token_url=http://localhost:4567/login"> <input type="hidden" name="openid_identifier" value="yahoo.com" /> <input type="image" src='https://a248.e.akamai.net/sec.yimg.com/i/yahoo.gif' /> </form>
This is the input form. Notice that it is entirely in HTML (it’s just a simple form submit with one post parameter). The actual work is done by auth.rb in the root folder:
%w(rubygems sinatra rest_client json).each { |lib| require lib}
get '/login' do
'You are logged in!' if authenticate(params[:token])
end
def authenticate(token)
response = JSON.parse(RestClient.post 'https://rpxnow.com/api/v2/auth_info', :token => token, 'apiKey' => <rpx API KEY>, :format => 'json', :extended => 'true')
return true if response['stat'] == 'ok'
return false
end
You will need to register an application in RPXNow. In this example, I’m reusing Chirp-Chirp’s application in RPXNow, which is why you see the post action is to the server chirp-saush.rpxnow.com. The token is the URL that RPX will redirect to after it authenticates the user. The pleasant surprise here is that it allows you to redirect to localhost, which eases the development effort. In this example also, I’m using Yahoo as the OpenID provider. RPXNow provides a host of other popular providers — in Chirp Chirp I actually used Yahoo, Google and Windows Live ID though it provides a lot more others. I used an image button to submit but that’s to prettify the page.
Notice that RPX redirects to the localhost with the URL ‘/login’. I created a get method for this, which in turn passes the returned token to the authenticate method. Inside this method, I used Adam Wiggin’s (of Heroku fame) really convenient rest-client library to send a post request with the token and the API key provided when you register for an application. I indicated that I want to receive the response in JSON. The response is parsed for the status and can also be parsed for data. For simplicity I didn’t return the Yahoo user information (but it’s a really small subset of data only) though I could potentially parse the JSON data for it.
And that’s it! You now have web application authentication by a third party provider, courtesy of RPX.
What if you don’t want to have a middleman like RPX to do web authentication? In this example, I was using RPX Basic, which is free because I’m using an rpxnow.com domain. If I want my own domain for authentication, I need to pay for commercial account with RPX (which is really their business model). An alternative is to use OpenID directly instead, which is very popular and doesn’t add too much complexity.
This is the input form for OpenID authentication, openid_auth.html:
<form method="get" action='/login'> OpenID identifier: <input type="text" class="openid" name="openid_identifier" size='50'/> <input type="submit" value="Verify" /><br /> </form>
The input requires the user to enter an OpenID identifier. If you’re not sure what an OpenID identifier is like you can check it out here. Most likely you’d already have one. Just like in the RPX case, the user is redirected to the OpenID provider, where he is requested to log in to that provider. After logging in, he will be returned to the calling application.
This is the Sinatra app that does this work, in a file called openid_auth.rb:
%w(rubygems sinatra openid openid/store/filesystem).each { |lib| require lib}
REALM = 'http://localhost:4567'
RETURN_TO = "#{REALM}/complete"
get '/login' do
checkid_request = openid_consumer.begin(params[:openid_identifier])
redirect checkid_request.redirect_url(REALM, RETURN_TO) if checkid_request.send_redirect?(REALM, RETURN_TO)
checkid_request.html_markup(REALM, RETURN_TO)
end
get '/complete' do
response = openid_consumer.complete(params, RETURN_TO)
return 'You are logged in!' if response.status == OpenID::Consumer::SUCCESS
'Could not log on with your OpenID'
end
def openid_consumer
@consumer = OpenID::Consumer.new(session, OpenID::Store::Filesystem.new('auth/store')) if @consumer.nil?
return @consumer
end
Note that it is not that much longer than the RPX code. I used the ruby-openid gem from JanRain, which is probably the defacto OpenID Ruby library. The steps are only a bit more complicated:
- The input form asks the user to enter an OpenID identifier and sends it to the ‘/login’ get block (it could easily be a post block)
- The ‘/login’ block first gets a consumer object. To create the consumer object, you need to pass in the session where you will store the request information (this is usually provided by the web framework) as well as a store. The store is the place where we keep associations, the shared secrets between the relying party (your application) and an OpenID provider as well as nonces, cryptographic one-time alphanumeric strings used to prevent replay attacks. In the example above, I created the store in the file system.
- Once we have the consumer, we initiate the start of the authentication process by calling its begin method with the identifier, which returns a CheckIDRequest object. This object contains the state necessary to generate the actual OpenID request
- Next we ask the CheckIDRequest object if we should send the HTTP request as a redirect or if we should produce a html post form for the user
- Then we either redirect the user to the OpenID provider or create a HTML form that does the same thing. Here we provide a return_to path for the OpenID provider to return the user to our application with a bunch of other data
- Once the user authenticates himself, he will be sent back to our application, and I used another get block ‘/complete’ to process the returned data
- We don’t need to go through the returned parameters one by one, we can re-use the same consumer object we created earlier and use the complete method to process those parameters
- The complete method returns a response object, which we can check for status
The process actually looks more complicated than it really is. The ruby-openid library simplifies the processing a great deal. In the example above, I only wanted to check if the user is valid or not, if I wanted to get more data on the user, there are a bunch of other things we can do.
We’ve just covered the web authentication. Let’s move on to client authentication, which doesn’t involve a browser. Google provides ClientLogin, which is an authentication API specifically desktop or mobile clients. Using it is actually simpler than web authentication. For this example and the next, I will use Shoes, the excellent Ruby GUI toolkit by why the lucky stiff. To run the code, you need to download and install Shoes, then follow the instructions on how to execute Shoes applications. I won’t go through how to create a Shoes application here though, that’s for another day. Here’s the complete code for using Google’s ClientLogin API, in a file called goog-auth-client.rb:
Shoes.setup do
gem 'rest-client'
gem 'net-ssh'
end
%w(rest_client openssl.so openssl/bn openssl/cipher openssl/digest openssl/ssl openssl/x509 net/ssh).each { |lib| require lib}
class GoogleAuthClient < Shoes
url '/', :login
url '/list', :list
def login
stack do
title "Please login", :margin => 4
para "Log in using your Google credentials!"
flow :margin_left => 4 do para "Email"; @me = edit_line; end
flow :margin_left => 4 do para "Password"; @password = edit_line :secret => true; end
button "login" do $me = @me.text; authenticate(@me.text,@password.text) ? visit('/list') : alert("Wrong email or password"); end
end
end
def list
title "You are logged in!"
end
def authenticate(email,password)
response = RestClient.post 'https://www.google.com/accounts/ClientLogin', 'accountType' => 'HOSTED_OR_GOOGLE', 'Email' => email, 'Passwd' => password, :service => 'xapi', :source => 'Goog-Auth-1.0'
return true if response.code == 200
return false
end
end
Shoes.app :width => 400, :height => 200, :title => 'Google Authenticator'
You might notice that I actually included a large number of libraries. This is because there is a problem in the current Shoes build, which didn’t include the OpenSSL libraries so we’ll need to add them in manually. The method to focus on is really the authenticate method. I used the rest_client library again to send a post request to the ClientLogin URL. the parameter ’service’ indicates which Google service you want to access. In our case, we just want to authenticate a Google user, so we can use the generic service name ‘xapi’. The ’source’ parameter is a short string that identifies our application, this is for logging purposes only.
An alternative to ClientLogin and just as easy is Twitter’s basic authentication service. The code is also exactly the same. Here’s the code, in a file named twit-auth_client.rb.
class AuthClient < Shoes
url '/', :login
url '/list', :list
def login
stack do
title "Please login", :margin => 4
para "Log in using your Twitter credentials!"
flow :margin_left => 4 do para "Username"; @me = edit_line; end
flow :margin_left => 4 do para "Password"; @password = edit_line :secret => true; end
button "login" do authenticate(@me.text,@password.text) ? visit('/list') : alert("Wrong user or password"); end
end
end
def list
title "You are logged in!"
end
def authenticate(user,password)
open("http://twitter.com/account/verify_credentials.xml", :http_basic_authentication=>[user, password]) rescue return false
return true
end
end
Shoes.app :width => 400, :height => 200, :title => 'Blab!'
Let’s jump into the authenticate method again. I used OpenURI to send a get request to the verify credentials API. Twitter uses basic authentication to protect its resources, so we need to pass in the user and password information as well (notice that OpenURI allows you to use basic authentication). I could parse the returned results, but what happens here is that if the user and password information is invalid, it will throw an error anyway, so I just do a rescue and return false. If all is well, I can just return true.
You might notice that the code that allows me to use both Google and Twitter as a the third-party authentication provider is just a single line! Don’t you just love Ruby?
Clone TinyURL in 40 lines of Ruby code
April 13th, 2009 by sausheong
Update: I deployed the same code to the Google AppEngine for Java and described how I did it here - http://blog.saush.com/2009/05/clone-tinyurl-with-40-lines-of-ruby-code-on-google-appengine-for-java/
I’m officially hooked. After writing 2 blog posts on cloning popular web applications on the Internet, I was raring to take on another one. TinyURL looked like the easiest so that’s the one I did. In fact it’s so easy there’s at least 100+ such applications in the market already. I called my TinyURL clone, Snip (http://snip.heroku.com).
I wrote Snip with Sinatra then deployed it up to Heroku so this is also a good excuse also to describe Heroku, a truly amazing service for the Ruby programming community. The total number of lines in Snip is actually 43, in a single file named snip.rb. including the view template and layout. To check it out go to git://github.com/sausheong/snip.git.
A quick word about TinyURL and its army of clones. TinyURL is the first of its kind (started in January 2002) providing a very simple but useful service of replacing a full URL with a much shorter one. Going to the shortened URL will redirect the user to the actual full URL. Its usage really exploded with the rising popularity of Twitter, which required its users to send messages in only 140 or less words, really making URL shortening a necessity. In March 2009, the service with second largest market share (13%) bit.ly, raised $2 million as funding and TechCrunch had a field day, even estimated that TinyURL with 75% of market share worth up to $46 million! Unfortunately till date, TinyURL’s actual business model and the question of it and its ilk can make money is still unanswered.
Source : TechCrunch
Enough on the business and money. Let’s look at the code and start with the first line. Most of the time we write require files in multiple lines, but actually we can use an array and iteratively require each of the library. I only used Sinatra and DataMapper libraries here though Sinatra itself includes HAML, which is the template markup language I used in Snip.
I will not go in depth on using Sinatra. If you’re interested, please go to the Sinatra documentation or my previous post. I will assume you roughly know how Sinatra works and jump right in (anyway there is so little code you’d probably understand it easily).
%w(rubygems sinatra dm-core dm-timestamps uri).each { |lib| require lib}
get '/' do haml :index end
post '/' do
uri = URI::parse(params[:original])
raise "Invalid URL" unless uri.kind_of? URI::HTTP or uri.kind_of? URI::HTTPS
@url = Url.first(:original => uri.to_s)
@url = Url.create(:original => uri.to_s) if @url.nil?
haml :index
end
get '/:snipped' do redirect Url[params[:snipped].to_i(36)].original end
error do haml :index end
use_in_file_templates!
DataMapper.setup(:default, ENV['DATABASE_URL'] || 'mysql://root:root@localhost/snip')
class Url
include DataMapper::Resource
property :id, Serial
property :original, String, :length => 255
property :created_at, DateTime
def snipped() self.id.to_s(36) end
end
__END__
@@ layout
!!! 1.1
%html
%head
%title Snip!
%link{:rel => 'stylesheet', :href => 'http://www.w3.org/StyleSheets/Core/Modernist', :type => 'text/css'}
= yield
@@ index
%h1.title Snip!
- unless @url.nil?
%code= @url.original
snipped to
%a{:href => env['HTTP_REFERER'] + @url.snipped}
= env['HTTP_REFERER'] + @url.snipped
#err.warning= env['sinatra.error']
%form{:method => 'post', :action => '/'}
Snip this:
%input{:type => 'text', :name => 'original', :size => '50'}
%input{:type => 'submit', :value => 'snip!'}
I have only 2 get blocks. The ‘/’ get block primarily just shows the main page, while the ‘/:snipped’ get block takes in the snipped code fetches the original URL, then redirects the user to it. I also have a post block. The ‘/’ post block (notice that using get will not reach the post block, which neatly demonstrates the pure simplicity of Sinatra) first makes sure that the URL is valid (by running it through the URI parse method). Then it either creates a new URL or fetches the existing one, if it was shortened beforehand.
A note on alphanumeric code used to represent a URL. I store each URL in the database as a row and the code is really just the row ID in the database table. However I cannot use the row ID directly because as the number of URLs grows, the number of characters representing the code grows quickly as well. For example, as I hit 1 million URLs, I would have 7 characters (all numbers) in the code. This is not so efficient. To reduce the number of characters used for representing the row ID, I use a base 36 numbering system (a-z, 0-9). This means 1 million records in the database would only require 4 characters (1,000,000 base 10 is ‘lfls’ base 36). And the 200 million records that TinyURL claims to store, will use only 6 characters instead of 9. I have no idea how TinyURL actually generates their code, but looking into their current number of characters in the code (6) I would say this is not a far off guess. (Reverse engineering their 6 character code this way though, results in showing that TinyURL have > 700 million records).
Doing base 36 conversion seems daunting but in reality most programming languages would have some sort of support for non-decimal numbering system conversion. Ruby’s implementation is particularly simple. A Ruby Fixnum (i.e. all whole numbers) has a method called to_s. This method is probably familiar with all Ruby programmers as it converts any object to a String representation. What is likely less well-known is that Fixnum’s implementation takes in a parameter, which is the radix for the base numbering system used. For example:
>>1234.to_s(2)
=> "10011010010"
>> 1234.to_s(36)
=> "ya"
Conversely, String’s to_i implementation does the reverse, which is to take a String and convert it into a Fixnum representation of that String, given the radix:
>> "hello world".to_i(36)
=> 29234652
For templating, I used HAML, the delightful albeit more programmer-centric templating system. Most templating systems strike a compromise between HTML and a programming language. This is evident in the popular systems like JSP, ASP, PHP and even ERB (ERB is the templating system used by default in Rails). However HAML abandons HTML altogether and goes for a purely programming approach, very much like Seaside (Seaside is a Smalltalk web application framework). Skipping comparisons on the difference approaches in templating, one advantage HAML has is that it allows programmers to code the interface in a more natural way, which just suits me fine in this case.
I used a Sinatra trick that allows me to embed the template within the same source code itself. While normally I would need to create 2 additional template files (1 for the layout and another for the index), I added in the code for the templates in the same source file but after the __END__ keyword.
To prettify the interface, I used one of the ready-made W3C core stylesheets, which provide me with a standard and well defined set of styles without going through the headache of creating one myself.
And we’re done! A full URL shortening service in a 40 lines of code file. To start it up just do this:
$ ruby snip.rbThen go to http://localhost:4567.
The next step is to deploy it to Heroku. I can’t say enough about this service, which is heaven-sent for the Ruby web application programming community. Just register an account here at http://heroku.com. In fact the main page more or less explains the steps you need to do to deploy the app! However, there are a couple more steps for Sinatra. Here is the complete list of steps:
1. Create a config.ru file
This is the Rack configuration file, which is actually just another Ruby script. All you need to have in this file is this:
require 'sinatra' require 'snip' run Sinatra.application
This tells Rack to include the Sinatra and Snip libraries, then run the Sinatra application.
2. Install the Heroku gem
$ sudo gem install herokuHeroku provides us with a set of useful tools packaged in a gem, very much like Capistrano.
3. Initialize an empty Git repository in the snip folder
$ cd snip
snip $ git init
Initialized empty Git repository in .git/
snip $ git add .
snip $ git commit -m 'initial import'
Created initial commit 5581d23: initial import
2 files changed, 52 insertions(+), 0 deletions(-)
create mode 100644 config.ru
create mode 100644 snip.rbThis just creates and initializes an empty git repository on your computer.
4. Create the Heroku application
sinp $ heroku create snip
Created http://snip.heroku.com/ | git@heroku.com:snip.git
Git remote heroku addedYou will be prompted for your username and password the first time you run a heroku command. Subsequently this will be saved in ~/.heroku/credentials and you won’t be prompted. It will also upload your public key to allow you to push and pull code.
5. Push your code to Heroku
snip $ git push heroku master
Counting objects: 4, done.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 999 bytes, done.
Total 4 (delta 0), reused 0 (delta 0)
-----> Heroku receiving push
-----> Rack app detected
Compiled slug size is 004K
-----> Launching....... done
App deployed to Heroku
To git@heroku.com:snip.git
* [new branch] master -> masterNotice that this pushes your code and loads your application into deployment.
6. Log in to the Heroku console and create the database
snip $ heroku console
Ruby console for snip.heroku.com
>> DataMapper.auto_migrate!
=> [Url]Heroku allows you access to a console similar to irb but with the environment of your deployment loaded up, like script/console in Ruby on Rails. To create the database, I just run DataMapper.auto_migrate! and it will create the database accordingly.
This is it! Now go to your application on Heroku and you should be able to see this:
One of the main sticking points in doing Ruby web application development is finding a place to host the application. Most people either do web host sharing or slice hosting but it is either underpowered or costly (or both) and requires mucking around with servers (which many application programmers like myself do so only reluctantly). Heroku is an amazing service that heralds a new way deploying Ruby web applications that saves the day for many Ruby programmers.
A final word on the URL shortening service. For a more full-fledged service, I would probably register a much shorter domain name (something like what is.gd has) and also add more features that provide statistics to each redirected URL and so on.
Why it is difficult to accept the realities of a downturn
April 7th, 2009 by sausheong
I bought a 17″ Sony Flatron monitor for $535 in 1999, one of my prized possessions that accompanied me during the few years which I hopped from rented room to rented room. It weighed almost 20kg and was a tremendous monster to lug around, maybe 20% of the total weight of my other stuff put together. I retired it (still working) when I got my Samsung 19″ LCD monitor ($220) about 2 years ago and my wife persuaded me to sell it off. However, I baulked when I was offered $50 by the karung guni man, after all, it was still working. So I refused to sell it.
The next time I mentioned it to a karung guni man, he wouldn’t even want to take it and wanted to charge me $5 to take it off my hands. Naturally I didn’t pay.
All these brought me to the couple of conversations I had with Winston and with Simon. Conversations that somehow drifted to talking about our lifestyles in the current state of the economy. Perhaps this was on my mind during our lunchtime chatter, since we talked about completely different things to begin with. Winston talked about how he struggled through his startup days to achieve where he is today. Simon and I talked about how people upgraded their lifestyles over the few good years before the current crisis, and having done so found it extremely hard to accept that they need to lower their expectations now. Stories of people who lost their jobs and cannot accept that their new jobs now pay 20% - 25% lower than their previous one. People who just bought their 42″ LCD TVs, high-end electronic gadgets, cars and even apartments, depended entirely on their salaries to pay for the installments and lost their jobs. People with shiny promising lives ahead of them during the prosperous times but now facing bleak, burgeoning loans and unable to come to terms with the new realities of a recession.
Which led me to think — what makes it so difficult for us to accept the realities of an economic downturn?
My guess is a combination of these three hypotheses:
Endowment effect
This simply means that people place a higher value on objects they own than objects that they do not. An experiment conducted in Duke University by Ziv Carmon and Dan Ariely showed how surprisingly irrational yet humanly plausible this is.
Duke University has a small basketball stadium which doesn’t have enough seats for all its fans so it designed an elaborate lottery system to allocate tickets instead. The experiment involved fans who has won tickets to an NCAA Final Four basketball tournament and fans who had not, 93 respondents in all. Each respondent was asked, one day prior to the match, to indicate their selling or buying price for a ticket to the match. The buying price question asked for the highest price he or she would pay for the ticket and the selling price question asked for the lowest price he or she would agree to sell. In addition, the would-be buyers would be asked to think of other items or experiences that would be equivalent in value to the tickets. The test was to find out how much the buyer value the experience as compared to an equivalent experience and how much the seller value losing that experience. In other words, it was an experiment to determine the existence of the endowment effect.
When the experiment ended, the 10% trimmed mean selling price was about $2,400 while the 10% trimmed mean buying price was about $170. That’s a difference by a factor of 14! Rationally speaking, the would-be buyer and the would-be seller should think of the experience in the same way since they were randomly picked fans. The only difference was that some of the respondents won a lottery for the ticket and others didn’t. It’s pretty hard to explain the differences between the selling price and the buying price but at the same time it is strangely familiar and human.
This is why it’s particularly bitter for us in this downturn — we have already owned our new lifestyle, and it has gained particularly high value. If we have not owned that brand new Honda Civic it wouldn’t have mattered so much, but now that we have it, losing it is much more painful, even though we had lived happily in the past without it.
Loss aversion
This again should be familiar to most of us. It refers to the tendency for people to prefer avoiding losses than to acquiring gains of similar value. For example, it is more painful to lose $1000 than it is pleasurable to gain $1000. Given a choice people would prefer the chance not to lose $1000 than the chance that they might gain $1000. In a 1981 paper by Amos Tversky and Daniel Kahneman, researchers described an experiment conducted at the University of Stanford and the University of British Columbia where 2 groups of students (152 and 155 respectively) were asked to answer this brief questionnaire in a classroom setting:
Imagine that the US is preparing for the outbreak of an unusual Asian disease, which is expected to kill 60 people. Two alternative programs to combat the disease have been proposed. Assume that the exact scientific estimate of the consequences of the programs are as follows:
If Program A is adopted, 200 people will be saved.
If Program B is adopted, there is a 1/3 probability that 600 people will be saved and 2/3 probability that no on will be saved.
Which of the two programs would you favor?
As it turns out 72% of the respondents chose Program A and 28% chose Program B. However, when the questions were phrased like this:
If Program C is adopted 400 people will die.
If Program D is adopted, there is a 1/3 probability that nobody will die and 2/3 probability that 600 people will die.
Which of the two programs would you favor?
the reverse happens i.e. 78% of the respondents chose Program D and 22% chose Program C! As you can see Program A and C are essentially the same, as with Program B and D. The difference was how the questions were worded. Whereas Program A describes people being saved (a gain) while Program C describes people dying (a loss). Intuitively it seems right, but it is still pretty startling that mere words could affect us this way.
Cognitive dissonance
Cognitive dissonance is one of the most influential and extensively studied theories in social psychology. It is the uncomfortable feeling when we have two contradictory ideas at the same time. The theory is that in such situations we would be driven to change or justify our attitude or behavior. For example, if you believe that you are a careful driver and an accident happens, you would normally either blame it on the other driver or some external factor that doesn’t contradict with your self-belief that you’re a careful driver.
In this economic downturn, the self-belief that we are worth this much (in terms of salary or other compensation) contradicts with the reality that we have been offered a job that is paying less. The cognitive dissonance then drives us to angrily reject the offer as being unreasonable, the employer is trying to take advantage of the downturn or some other justification that doesn’t take away that self-belief.
So?
So what can we learn from this? Loss aversion tells us that looking at it in a different perspective makes things less painful for us. It’s not losing a job, it’s galvanizing us to try out the other stuff we’ve always been too busy with. What we learn from the endowment effect is that losing our stuff is painful. That will not go away. However we can make things less painful not only by spending only we can afford, but also spending a few levels less than what we can afford in order to buffer for this pain. I can afford that Honda Civic if I have my job and current salary, but shouldn’t I buy a cheaper car such that I can afford it even if I lose 50% of my salary? Finally, cognitive dissonance is part of human nature but what we can’t change, we should adapt. Recognizing that our self-worth is not measured in terms of our salaries but other things our families and friends, that salaries and jobs, like most things in the world goes through cycles should give us better sanity in dealing with a rapidly changing economic crisis.
Having knowledge of what makes is hurt so much in this downturn doesn’t really help us get back our jobs or salaries. But knowing that it is human to feel this way, and that everyone is feeling the same way probably helps us face it better.
I still have that 17″ Sony Flatron monitor lying somewhere. One of these days I will need to overcome the endowment effect and dump it.