Monday, July 30, 2007

Hudson Unleashed...

It has been more than a month now since I started using hudson and I thought I'd give an update on the progress and on what I've found...

Let me say to kick things off that Hudson has handled everything I've thrown at it. There are now upwards of 50 projects being built by Hudson and hudson shows no sign of falling over or being thrashed too much. Furthermore, the front end is still as responsive and quick as ever.

It has a particularly active development community with the primary developer being active in the forums and also active in terms of working on the project. A new version is released about twice a week.

Hudson supports dependent builds iow, a build can be kicked off by the completion of another build. So what I've done is setup each one of our projects in Hudson. Hudson monitors the repo for changes to those projects and then builds them. If there are dependent projects, those projects are also built. Because of this I can make the polling interval and "wait time" very short. Developers know within a minute or two whether a checkin broke the build (compile errors). Sometimes unfortunately there is a false positive because of ordering issues, but that is acceptable.

Furthermore, because of this facility I can always have an EAR ready to be deployed. I get to re-use the result from one build in another build. The primary mechanism I used to do this was for the build to copy the generated jar to some shared location on the drive. It would be better to use a tool such as ivy to publish the jar because then I can leverage hudson ability to distribute builds to other machines (v. nice).

I've since discovered however, that if I publish the jar with hudson, then I can use hudson to distribute the jars. This is because hudson publishes the jar to a static url and I can get the jar via the static url. It's great - a lot lighter than putting ivy in.

Furthermore something very funky, is that you can fingerprint jars. If you tell hudson to fingerprint jars then it can tell you which builds used those jars. You need to fingerprint the jar both in the source project and in the dependent project for this to work. The key issue here is that you do not have to rename the jar every time. So if there is a build error with a downsteam build and you suspect it's caused by an upstream project, you can tell exactly which upstream build number the downstream build is using.

Hudson is just done well, and often it is in the small things that this comes through. One other example of this is hudson's ability to run arbitrary batch/shell commands. The command that you specify is not simply dumped to the console and run, but rather the command is dumped to a batch file and then that batch file is run. Very nice little consideration because with one sweep you allow multiple commands to be run! Very useful. I was able to create a hudson task to restart jboss for instance.

It's a great application, and if you haven't got a Continuous Integration server running in your environment, do yourself a favour and set it up, if you do, and it's not hudson, do yourself a favour, and set it up!

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