Wrapping each Hudson distribution in its own RubyGem

Charles Lowell

January 06, 2011

Update: As of version 1.396, this is applicable to the Jenkins project. 1.395 will be the last version of the hudson-war gem

As you may or may not know, we here at The FrontSide have been working since late last year to create a proper ruby environment for extending hudson. This is no mean feat because it implies not only the ability to use nothing but ruby code to implement hudson plugins, but just as importantly, the ability to use nothing but ruby tools to develop them. That means no javac, no jar files, no war files, and for the love of all that is holy: absolutely, positively, no maven. In short, the only folks you'll need to know to get in the door with Hudson are your pals Ruby, Rake and Bundler.

Of course, all those jars and wars and perhaps some class generation will be there behind the scenes. After all, we'll still need to compile java stubs that depend on core Hudson classes. We'll still need to package your plugin along with its ruby code and dependencies in a jar file, and we'll still need to take care of all the blah, blah, MANIFEST, blah, META-INF, WEB-INF, blah, blah, blah...

The War

If we're going to do the compilation against Hudson core from within ruby and Rake instead of maven, then we're going to need a reliable way to get at the core hudson classes so that we can use them in our compilation classpath. Not only that, but as part of the development process, you're going to want to test your plugins against a fully functioning hudson server. Luckily, both of these are contained in the full hudson distribution that you download as a single war file. Wouldn't it be nice if you had a simple way to get at a specific version of one of those wars and then get at all those java goodies contained therein?

The Gem

To my thinking, this sounds like a job for: RubyGems! That's why we're introducing the new hudson-war gem, which does nothing except wrap a single hudson distribution so that it can be managed coherently just like any other ruby component. Want the latest warfile?

gem install hudson-war

Or perhaps you need hudson 1.386? That's fine, hudson-war versions are the same as the hudson distributions they wrap.

gem install hudson-war --version 1.386

It's not just a war file either. In keeping with the best traditions of OOP data comes bundled with behavior. The gem comes with a ruby API and a CLI baked in to help us do all the nifty things we might want to do with a war file. For starters, you might want to know where it is.

legolas:~ cowboyd$ hudson.war location

If you want to unpack it to a particular location then

legolas:~ cowboyd$ hudson.war unpack tmp
jar xvf /Users/cowboyd/.rvm/gems/ruby-1.8.7-p174/gems/hudson-war-1.386/lib/hudson/hudson.war -C tmp/

You can run a test server with it

legolas:~ cowboyd$ hudson.war server --daemon
Forking into background to run as a daemon.
Use --logfile to redirect output to a file
legolas:~ cowboyd$ hudson.war server --kill

Beyond the basics, let's say you want to do something interesting like compile some java code against the hudson core. You're gonna need a classpath, and you can get it with:

legolas:~ cowboyd$ hudson.war classpath

You can even compile java code with it directly. Here we compile a trivial class that has a dependency on hudson.

legolas:~ cowboyd$ cat > ImportsHudson.java
import hudson.model.Hudson;
public class ImportsHudson {
  public static void main(String args[]) {
    System.out.printf("The Hudson Model object's class is %s\n", Hudson.class.getName());
legolas:~ cowboyd$ hudson.war javac ImportsHudson.java
legolas:~ cowboyd$ java -cp .:`hudson.war classpath` ImportsHudson
The Hudson Model object's class is hudson.model.Hudson

It's like RVM for hudson. Wrangling java has never been so fun!

The War Gemmer

Befitting a continuous integration project, the Hudson team releases a new version at least every two weeks, and sometimes even sooner. It can be a bitch to keep up with, so I've set up a wargemmer hudson task to periodically poll the update center to see if there is a new release. If there is, it'll gem it right up and push it to rubygems. No fuss no muss.

Let the war begin!

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