Making the case for Scala

At first glance, Scala seems like an odd choice for developing web applications. Scala is a JVM language created by Martin Odersky of EPFL seems like an academic's testbed for a 'grand unified language' combining functional programming and strict object-oriented design. Scala is clearly gaining in popularity, but the current TIOBE Software Index places Scala at #24 with a rank of only 0.459%, far behind the #1 language, Java, which has a a rank of 17.348%. So, if you want to be on a JVM, why not stay with the undisputed champion of the TIOBE ranking since June 2001?

The key reason is money. Developer time is money. Developer time is, to a remarkably good approximation, proportional to the number of lines of codes that need to be written. This holds over a wide range of languages. Rather than regurgitate an existing piece, I urge you to read Research: Programming Style and Productivity and Scala vs Java: Conciseness equals less bugs. Scala was found to reduce lines of code by 30-35%. This should lead to a commensurate increase in productivity.

The second reason is that functional programming looks like it is the future. Erlang proves that functional programming can lead to high reliability systems with massive concurrency. Computers are becoming highly concurrent, not faster.

The third reason is more prosaic. Liftweb gives many of the advantages of Ruby on Rails and it also provides type checking. Call me old fashioned, but I get warm fuzzy feelings knowing that a compiler is preventing wide classes of errors.

The last reason is still in the future. In 2002, Phil Bagwell wrote Fast Functional Lists, Hash-Lists, Deques and Variable Length Arrays. He introduced new data structures for functional programming. Bagwell is Swiss and is at EPFL, where Martin Odersky works. So EPFL is the center of Scala. I learned about these by watching Rich Hickey's QCon London 2010 talk, Persistent Data Structures and Managed References. The slides are available on Michael Galpin's blog entry Persistent Data Strictures. This excites me, because many of the ideas of state took me back to physics, especially statistical mechanics. The talk, and Clojure's approach to state just seems right. So why is this a reason to use Scala!? Why not cut to the chase and go right to Clojure? At this point, I don't know, that may be the right answer. But Scala is a bit of a chameleon, and it seems to me that the concepts of State and Identity, as well as the persistent data structures that make this efficient, will be implemented soon in Scala. Scala 2.8 is getting Bagwell's VLists.

Suddenly, this is becoming an interesting time to be a programmer, and the JVM seems to be the epicenter of these changes. The JVM is very robust - there has been a decade of work with theorem provers that demonstrate the robustness of the design. There has also been a decade to flush out the bugs. Now, Scala, Groovy and Clojure are leveraging the JVM, and the plethora of libraries on the JVM. Full speed ahead!

David Pollak's Web Framework Manifesto

The best part of blogs is that is makes it possible for people with clear ideas, not just fame or access to money, to be published. David Pollak certainly falls within the category of clear thinking people, and his Web Framework Manifesto, from November 2006, is a great technical summary of what we all should expect of a web framework. It is fascinating to see the breadth of frameworks that he has examined.

Security figures predominantly in this manifesto. He states:

There should exist an orthogonal security layer such that objects that are not accessible to a user should never be returned in a query for the user and fields on an object that are not accessible should not be visible. The security and access control rules should be algebraic and demonstrable during a security audit. This means that neither the view nor the controller should have to test for access control. Objects and requests should be sanitized before they get to the “controller.”

At first, this seems like Spring Security, but the algebraic caught my eye. I don't know what this means. A Google search found Beyond Separation of Duty: An Algebra for Specifying High-level Security Policies, but this seems quite theoretical at this point. In the IEEE Security & Privacy Journal, the article, A Metrics Framework to Drive Application Security Improvement, describes a more pragmatic, but still quantitative approach to security.

David then went on to create and act as benevolent dictator for life of the Liftweb framework, or just Lift. As a benevolent dictator, it is no surprise that the key ideas of the Web Framework Manifesto are all present in Lift.

Liftweb 1.1 and Google AppEngine

With only minor modifications, I have repeated Joe Kutner's installation of Liftweb on AppEngine. I'm running OS/X, so I started by using macports to install maven2. I saw that Java App-Engine was just updated to 1.3.1, so that was installed and I adjusted my APPENGINE_HOME and M2_HOME in .profile. The latest liftweb version is 1.1-M8, so I'll try that one.

Now that I know I have updated libraries, I generated a liftweb project with:

mvn archetype:generate -U -DarchetypeGroupId=net.liftweb

-DarchetypeArtifactId=lift-archetype-blank -DarchetypeVersion=1.1-M8

-DremoteRepositories=http://scala-tools.org/repo-releases

-DgroupId=com.folkertsfotografie. rlftest -DartifactId= rlftest

Rather than using -Dversion=1.0-SNAPSHOT, I entered a version of 1.1-M8 when prompted in maven. As usual, then next commands were cd rlftestl and a quick mvn jetty:run to see that http://localhost:8080/ was working. As an eclipse user, I added mvn eclipse:eclipse. So far, so good. The simple helloword application came up normally under the jetty installed with liftweb.

To integrate with AppEngine, I just added the boilerplate appengine-web.xml in my WEB-INF directory. The contents are:

<?xml version="1.0" encoding="utf-8"?>

<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">

<application>rlftest>

<version>3</version>

<system-properties>

<property name="in.gae.j" value="true" />

</system-properties>

<sessions-enabled>true</sessions-enabled>

<static-files>

<exclude path="/**" />

</static-files>

</appengine-web-app>

With that done, I built the war file with mvn package. To run that war file under AppEngine, just type

$APPENGINE_HOME/bin/dev_appserver.sh target/rlftest-1.1-M8.

That also worked, I could see http://localhost:8080/. Finally, I published this to appsite with $APPENGINE_HOME/bin/appcfg.sh update target/rlftest-1.1-M8.

With that done, I browsed my AppEngine control panel and tested that the hello world application. It worked without a hitch. Now, I can get back to learning liftweb and Scala. It isn't at all clear to me how liftweb and datastore will work together, but I'll just have to burn that bridge when I get to it. So thanks Joe, you have been a great help getting me started with Lift.

Google Analytics: integration with web apps.

Google Analytics is a powerful, free tool to gather information on events in the click streams of your website's visitors. I'm trying to develop a web application for photographers, starting with my wife's site, folkertsfotografie.com. I'm tracking progress on fotositeproject and the new webapp is running on GAE, Google App Engine. This is a rather Google-centric project. I'm using Picasa to hold image galleries. The RSS from Blogger, Picasa and flickr are being integrated using Google's Feed API via the jQuery library jGFeed. So when we wanted to add analytics, Google Analytics was on the top our our list.

I had hoped to develop with Grails, but it has proven to be too slow. This is a known issue, and both Google and SpringSource are working on speed ups. I switch to Gaelyk, a lighter Groovy framework for GAE, which is resulting in reasonable performance. I looked at GAE sites using other Java frameworks, and was surprised how much faster they are. However, GAE also has similar issues with Rails on jRuby, presumably for the same architectural reasons. GAE performance with Groovy is still an issue, but one that I trust will have a happy ending in the next few months. GAE does a lot of validating of included libraries on startup, which is probably a really good thing for security. I wonder if they can have some standard pre-verified jar files for groovy, jruby, grails, sitemesh and so on. When I want to use one of these jars, I agree to use the 'Google compatible version'. When I load my app, they check the MD5 hash to make sure that I am still using an unadulterated copy & they can just copy their jar image into my application's memory without the expensive validation. Can't we pay this price once when we load the app, not every time we start it up? There is still activity in the Grails community to develop GAE integration, so I can't believe that this issue will remain for long.

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Returning to my original topic: Google Analytics requires adding some code snippets to the bottom of each tracked 'page' or in the event handlers for tracked events. In a MVC design, the code snippets must resign in the views. However, the URLs are tied to controllers, so the keys for each URL need to be managed by the controller. I had assumed that a quick search would find others who had discussed this topic. Surprisingly, this is not the case. I have written a page that will read a Picasa RSS feed and then show the album in Galleriffic, a terrific jQuery image gallery. I want to have URLs like /gallery/show/sarah2009, so I don't want to place 'the key' in a file like /album/show.gsp, since the controller don't even expose that URL to the user. I certainly want to track patrick2009 with a different code that campingTripSpring2007, even if they both use the same view. So for each controller, I need a map of the view, the model, Google Analytics keys to use. This isn't quite model data, since the model should only have 'domain' data, which in this cased is information about the albums, media feeds, images, models and clients. It seems that only the controller is in a position to address this.

REST and application evolution

REST turns out to be the key to allowing software to be upgraded without breaking applications. The idea is pretty simple,you agree on the small number of REST verbs. You then have interfaces that are specified by URL and a version number (perhaps part of URL). You then allow clients to specify their version number in a request.

This is discussed in a couple of InfoQ talks. Alex Antonov gave Case Study: RESTful Web Services at Orbitz. He shows how Protocol Buffers allow for efficient (he claims 7 times faster than SOAP) and flexible message passing using HTTP. Protocol Buffers is an open source HTTP messaging protocol developed by Google. The exchanged data uses protobuf.

Steve Vinoski gives a great talk on RPC and its fundamental flaws. He was an expert in CORBA in the 90's and he has recently moved to REST and Erlang. He is quite convinced that functional programming is the future and that imperative languages, such as Java and C# are based upon a the wrong model of distributed programming.

These talks dovetail nicely with Kirk Wylie's earlier InfoQ talk, Restful approaches to financial systems.

Google Sites - easy project web sites

I'm working with my wife to develop a web site for her business, FolkertsFotografie. Currently, it is a Smug Mug site. She isn't a fan of selling images via shopping carts, so SmugMug is not a special advantage. I'm wanting to learn about Google AppEngine, so we set up a 'project' to make this happen.

This is where Google Sites fits in. I wanted to organize all of the brainstorming, designing and so forth. Google Sites makes it easy. See for yourself at Fotositeproject. There is easy integration with a host of Google tools, such as Google Docs, Calendar, Groups, Analytics and Webmaster Tools. Plus, I can rest knowing that I have offsite backup of everything and I do not have to worry about keeping the servers running 24/7.

Google Analytics & Webmaster Tools gives me as much monitoring data as my employer gets from IT. But unlike me, Google provides IT services for free.

Grails: By the numbers

Everybody likes to talk about highly productive environments, but numbers are notoriously hard to come by. This makes alterlab's ALTERthoughts Blog, entitled Grails vs. Rails especially interesting. Using Java J2EE as a base, both Ruby on Rails and Grails were found to be twice as productive. Grails beat Rails, but by a margin so slim it seems a dead heat.