Doing more with less; very continuous integration 02 Sep 2009
miscellaneous software development hudson

Once upon a time I was lucky enough to take an “Intro to C++” class taught by none other than Bjarne Stroustrop himself, while I learned a lot of things about what makes C++ good and sucky at the same time, he also taught a very important lesson: great engineers are lazy. It’s fairly easy to enumerate functionality in tens of hundreds of lines of poorly organized, inefficient code, but (according to Bjarne) it’s the great engineers that are capable of distilling that functionality into it’s most succinct form. I’ve since taken this notion of being “ultimately lazy” into my professional career, making it the root answer for a lot of my design decisions and choices: “Why bother writing unit tests?” I’m too lazy to fire up the whole application and click mouse buttons, and I can only do that so fast; “Why do you only work with Vim in GNU/screen?” I can’t be bothered to set up a new slew of terminals when I switch machines, and so on down the line.

Earlier this week I found another bit of manual work that I shouldn’t be doing and should be lazy about: building. The local build is something that’s common to every single software developer regardless of language, Slide being a Python shop, we have a bit more subtle of a “build”, that is to say, developers implicitly run a “build” when they hit a page in Apache or a test/script. I found myself constantly switching between two terminal windows, one with my editor (Vim) and one for running tests and other scripts.

Being an avid Hudson user, I decided I’d give the File system SCM a try. Very quickly I was able to set up Hudson to poll my working directory and watch for files to change every minute, and then run a “build” with some tests to go with it. Now I can simply sit in Vim all day and write code, only context-switching to commit changes.

Setting up Hudson for local continuous integration is quite simple, by visiting you can download hudson.war which is a fully self contained runnable version of Hudson, you can start it up locally with java -jar hudson.war. Once it’s started, visit http://localhost:8080 and you’ve find yourself smack-dab in the middle of a fresh installation of Hudson.

First things first, you’ll need the File System SCM plugin from the Hudson Update Center (left side bar, “Manage Hudson” > “Manage Plugins” > “Available” tab)

Installing the plugin

After installing the plugin, you’ll need to restart Hudson, then you can create your job, configuring the File System SCM to poll your working directory:

Configuring FS SCM

Of course, add the necessary build steps to build/test your software as well, and you should be set for some good local continuous integration. Once the job is saved, the job will poll your working directory for files to be modified and then copy things over to the job’s workspace for execution.

After the job is building, you can hook up the RSS feed (http://localhost:8080/rssLatest) to Growl or some other form of desktop notifier so you don’t even have to move your eyes to know whether your local build succeeded or not (I use the “hudsonnotify” script for Linux/libnotify below).

By automating this part of my local workflow with Hudson I can take advantage of a few things:

  • I no longer need to context switch to run my tests
  • I can make use of Hudson’s nice UI for visually inspecting test results as they change over time
  • I have near-instant feedback on the validity of the changes I’m making

The only real downside I can think of is no longer having any excuse for checking in code that “breaks the build”, but in the end that’s probably a good thing.

Instead of relying on commits, you can get near-instant feedback on your changes before you even get things going far enough to check them in, tightening the feedback loop on your changes even further, very-very continuous integration. Your mileage may vary of course, but I recommend giving it a try.