Hudson, At Your Continuous Integration Service

I love Hudson. I have previously been a CruiseControl fan, but no longer. Hudson just works and has some excellent integration features with Maven2 and Subversion.

Generally, Hudson does this kind of stuff you would expect from a CI engine:

1. Easy installation: Just java -jar hudson.war, or deploy it in a servlet container. No additional install, no database.
2. Easy configuration: Hudson can be configured entirely from its friendly web GUI with extensive on-the-fly error checks and inline help. There's no need to tweak XML manually anymore, although if you'd like to do so, you can do that, too.
3. Change set support: Hudson can generate a list of changes made into the build from CVS/Subversion. This is also done in a fairly efficient fashion, to reduce the load of the repository.
   
4. RSS/E-mail Integration: Monitor build results by RSS or e-mail to get real-time notifications on failures.
5. JUnit/TestNG test reporting: JUnit test reports can be tabulated, summarized, and displayed with history information, such as when it started breaking, etc. History trend is plotted into a graph.
6. Distributed builds: Hudson can distribute build/test loads to multiple computers. This lets you get the most out of those idle workstations sitting beneath developers' desks.
7. Plugin Support: Hudson can be extended via 3rd party plugins. You can write plugins to make Hudson support tools/processes that your team uses.

Then the cool stuff kicks in!

Since each build has a persistent workspace, we can go back in time to see that workspace to trace what happened. This means Hudson can do after-the-fact tagging and has permanent links to all builds, including "latest build"/"latest successful build", so that they can be easily linked from elsewhere.

I really like the matrix style jobs that you can create. For a matrix build, you can specify the JDK version as one axis and a slave Hudson (distributed builds) as another axis. Add to that a third axis of arbitrary property/values pairs that your build understands and can act on (e.g. think, maven -PmyProfile or -Dapp.runSystemTests=true or -Ddatabase.flavor=mysql). This is powerful stuff right out of the box to support multiple compilers, OSes, etc., without having to create a new job for each configuration.

For maven 2 projects, Hudson will autodiscover the <modules> in a multiproject build and list them as sub-jobs in Hudson, complete with their own status and viewable workspaces. Links to project artifacts are linked to from the build status pages.

The plugins are also starting to become plentiful. There are plugins for JIRA and Trac integration, code violations charting, publishing builds to Google calendar!, and many more. The one with the most potential I think is the Jabber plugin. Not only can it send IM notifications to an individual or a group, but the newest (cvs head) version comes with a bot that you can interact with to schedule builds, get project statuses, and monitor the build queue.

As always, sometimes small things mean a lot. An example I appreciate in Hudson is seeing the build in progress scrolling by via the browser. For CruiseControl, you would have to login to the build box and "tail -f" to get the same real-time information.

I'm not a groovy fan yet, but I was blown away when I found a built in groovy console right there in the web UI! You can use for trouble-shooting and diagnostics of your builds or plugins.

All in all, I am really, really impressed with Hudson as a product, and with the support and development going on around it. There is a new version released literally every week. It makes me, for the first time, want to contribute to an OSS project. This is good stuff. Check it out.