Sydney BarCamp 3 this Weekend!

BarCamp Sydney is two days long this year, and will span the whole of the coming weekend (5-6 April). I'll be there on Saturday. It's usually quite a fun event, lots of good sessions and you're quite free to move around and find something that interests you. Part of the BarCamp manifesto is that you should also contribute as well as listen - I'll probably give a JRuby talk and demo.

Hope to see you at BarCamp!

3 04 2008

“JRuby: Enterprise 2.0” Slides

Here's the slides from “JRuby: Enterprise 2.0″ from our recent talks at Sun Tech Day and the ACS Web Technologies SIG.

7 03 2008

“JRuby: Enterprise 2.0” Presentations

Josh Price and I will be co-presenting at the Melbourne Sun Tech Day and the Sydney ACS Web Technologies SIG. Here's the low down:

JRuby: Enterprise 2.0
There's a lot of buzz around JRuby in both the Java and Ruby communities, for good reason. This talk will give you a whirlwind introduction to JRuby. We'll show you why JRuby is regarded as such a powerful and dynamic development platform. We'll also suggest where to use JRuby in product development and the enterprise and how to leverage your existing Java investments.
There will be sample applications, live demos and not many slides.

Sun Tech Day Melbourne
4 March 2008, 2:30pm
More info on Sun site...

ACS Web Technologies SIG Sydney
5 March 2008, 6:15pm
More info on ACS site...

Hope to see you there!

23 02 2008

Practical JRuby on Rails (Web 2.0 Projects) by Ola Bini

The fine folk at Apress sent me a copy of Ola Bini's new book to review. The full title is "Practical JRuby on Rails Web 2.0 Projects - Bringing Ruby On Rails to the Java Platform". Overall, it was a good read, and extremely valuable to anyone who is developing in JRuby. JRuby information and documentation is scarce and most of the time, a Google trawl does not give you good results on a JRuby related query. Ola's is the first, and currently the only JRuby book available, and in my experience, the most valuable resource available to give you an all-round picture of JRuby capabilities and usage.

Audience
Despite comments on the cover, I would suggest that this book is not ideal for people new to Ruby / Rails. Ola jumps in the deep end quite quickly, and being a talented Ruby programmer, makes use of lots of shorthand, procs, code blocks etc which would likely be hard to follow for someone new to Ruby. Although there is a section at the back called "Ruby for Java programmers", I think this would not be sufficient for somebody new to Ruby to understand all the code examples.

To get the most value out of the book, it would be good to have at least a basic understanding of Ruby and Rails (eg, having read Agile Web Development with Rails or messed around with Ruby/Rails a bit) and a basic understanding of Java syntax, deployment and Java EE.

What's Covered?
The book is project based, so as to give context and useful examples of JRuby functionality. There are 4 projects:

  • The Store (Shoplet) - a standard Rails app running under JRuby using Active Record JDBC.
  • Content management system - general Java integration and using Java libraries for content rendering.
  • Administration System - using EJBs, JMX and discussion of JRuby deployment options.
  • Library System - JRuby as the "glue that never sets". Using Java Web service frameworks and JMS from JRuby.

The Good

  • Teaches you how to do all those tricky bits which are half-Java and half-Ruby and can't be easily found online, such as converting between Ruby and Java types, including JAR files, implementing Java interfaces, etc
  • Clever and concise Ruby code - I picked up some Ruby tricks reading Ola's code.
  • Complex code snippets are generally well explained in text.
  • Useful tips on when to use Java libraries and when to use Ruby ones.
  • Generally good and interesting example projects which justified the use of JRuby and the techniques shown in the book.
  • Helpful discussion of JDBC and database connectivity options for JRuby.
  • Nice overview of the many JRuby deployment options.
  • Helpful "sidebars" about Java Enterprise Edition technologies.
  • Covers the strong areas of JRuby well - web applications and system integration.
  • Appendices provide useful reference information.
  • Nice section at the end on how you can get involved in JRuby.

The Less Good

  • Example views often contain table layouts, inline styles and other layout information that would be better done in separate CSS files.
  • Variable names in code could be more descriptive. This would make example code easier to follow.
  • Occasional odd spelling like "sur_name" and use of deprecated Rails features, such as "start_form_tag" (to be fair though, Rails API does change very quickly).
  • The title suggests that the book is about Web 2.0. There is a little token AJAX, and I suppose a content management system is a bit Web 2.0, but overall, buy the book if you want to know about JRuby, not Web 2.0.
  • Although REST is only mentioned briefly in a little sidebar, and not a focus of the book, I found the description of REST and CRUD a bit misleading, especially when considering PUT vs POST.
  • The discussion of JRuby deployment provides a good overview, but more in depth discussion of major options (eg, GoldSpike), and production configurations would be great.

Conclusion
As the best and only JRuby reference, I'd highly recommend you buy a copy if you are working in, or planning to work in JRuby. The book will help you to write JRuby applications which make good use of Ruby, Rails, Java libraries and Java Enterprise Edition features.

16 12 2007

JRuby on Rails with GoldSpike – Scaling for more users

The default configuration for running JRuby on Rails using GoldSpike only allows 4 instances of the JRuby runtime. This means that if there are more than 4 simultaneous requests from clients, the web server will respond with a server overloaded error. The easiest way to see what's going on is to take a look at the 'createObjectPool' method of RailsServlet.

With a dedicated production server with 1gig of memory, it is possible to allow a lot more JRuby runtimes, and hence allow for more simultaneous users. A little load testing on a fairly small app suggested that 20 instances of JRuby runtime would fit comfortably under the 1gig ceiling and not overload the processor.

An easy way to change the max number of runtimes is to edit 'web.xml' in a JRuby application's WEB-INF directory. Parameter is set as follows:

  <context-param>
    <param-name>jruby.pool.maxActive</param-name>
    <param-value>20</param-value>
  </context-param>

It is also worth checking with the web server configuration to ensure that the web server allows more threads than the number of JRuby runtimes specified in 'web.xml'.

26 09 2007

JRuby, Rails and Statics

Say you wanted to store some information across different calls to your JRuby/Rails application on the server side. You could use a database, or memcached. However, what if you just want to do something very simple like a basic cache, and you don't have a database for your application? Memcached seems like overkill, and would complicate your deployment considerably. So, what about just using statics?

Well, you can't do it in Ruby, as the Rails integration servlet spawns multiple instances of the JRuby interpreter.

Ruby code in a page view:

<h1>Ruby global number</h1>
<% $i ||= 0 %>
<% $i += 1 %>
<%= $i %>

<h1>Ruby obj id</h1>
<% $o ||= Object.new %>
<%= $o.object_id %>

Results between multiple refreshes of the page:

Ruby global number
1 
Ruby obj id
244 

Ruby global number
1 
Ruby obj id
256 

Ruby global number
2 
Ruby obj id
244 

Ruby global number
2 
Ruby obj id
256 

Our requests seem to be switching between two instances of the Ruby interpreter.

However, we *can* do it in Java. My clever, Java-literate colleagues explained that Java application servers and servlet containers use a single instance of the JVM, but have a class loader for each application. The class loader stores class information and static values. This means that within one application, the static values will be maintained between requests, but a different application on the same server will have its own set of unrelated static values (similar to AppDomains in .NET).

If we add a call to a static method in Java that increments an integer and returns it, our view looks like this:

<h1>Ruby global number</h1>
<% $i ||= 0 %>
<% $i += 1 %>
<%= $i %>

<h1>Ruby obj id</h1>
<% $o ||= Object.new %>
<%= $o.object_id %>

<h1>Java incrementing static integer</h1>
<%= TestClass.incrementAndReturnNumber() %>

Our results now look a lot more useful. The Java static integer is getting incremented each call to the view:

Ruby global number
1 
Ruby obj id
244 
Java number
1 

Ruby global number
1 
Ruby obj id
256 
Java number
2 

Ruby global number
2 
Ruby obj id
244 
Java number
3 

Ruby global number
2 
Ruby obj id
256 
Java number
4 

From this little experiment, Java statics seem like a possible way to go for storing temporary data on the server side (eg, a cache implemented as a singleton) for JRuby / Rails. Another option may be to use the ServletContext from the JRuby Rails integration servlet - probably an area worth investigating.

9 09 2007

BarCamp Sydney this Saturday

It is BarCamp in Sydney this Saturday. I haven't been to one of these unconference style events before, but I've heard good things about it from my colleagues. I'm quite excited to go along and see what it is like.

If you're in Sydney and interested in stopping by, details are as follows:

When: Sat 25th August 2007 from about 9am
Where: University of Technology, Sydney (Jones St entrance)
More details...

One of the novel aspects of BarCamp is that all participants are encouraged to present or start a discussion around something that interests them. For my part, depending on what people are interested in, I was thinking of one of the following:

  • new stuff in the .net space (C# 3.0, .NET 3.5, LINQ, WPF, WCF, etc) and showing some demos
  • giving a bit of a Ruby/JRuby introduction with help from Ola's JavaBin slides
  • or, if people are keen, a discussion around JRuby vs C# 3 vs Java vs ?? and their stacks for different situations and problems
    • By the way, the conference is free, and it is not too late to sign up 🙂
      Hope to see you there!

22 08 2007

JRuby Setup

Recently got a JRuby/Rails system with Java integration up and running. Unfortunately, it took quite a few hours, as most of the docs and code you find through Google are out of date.

If you use JRuby 0.9.2 from Codehaus, you will get an error similar to this when you try to access a rails application:

[2007-02-26 17:54:59] INFO WEBrick::HTTPServer start: pid=22540508 port=3000
<ArgumentError: Anonymous modules have no name to be referenced by>
["c:/jruby-0.9.2/lib/ruby/gems/1.8/gems/activesupport-1.4.1/lib/
active_support/dependencies.rb:402:in `to_constant_name'...

If you're stuck in this rut, fear not! Nick Sieger has written very helpful instructions which outline how to get and set up the latest development snapshot. Please note that in addition to the instructions, you need to set your JRUBY_HOME environment variable. Under Windows, do something like this:

set JRUBY_HOME=c:\jruby

If you'd prefer not to use the snapshot, you can get the source code through subversion from:

http://svn.codehaus.org/jruby/trunk/jruby

but at the time of this post, you need to run svn checkout or update with "--ignore-externals" to avoid the following error:

Error: URL 'svn://rubyforge.org/var/svn/bfts/bfts/trunk' doesn't exist

Many thanks to Nick Sieger and the JRuby user mailing list for their help.

26 02 2007