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Thu, 12 Aug 2004

This is an archived blog post. I've switched to using WordPress as my blogging software and have not migrated all my old posts. I believe strongly in not letting an old link die, so this page continues to work. Please do visit mikemason.ca/blog to read newer posts.

Continuous Integration is the practice of building your software many times a day, usually whenever a change is checked into source control, so the development team can find out quickly if they’ve broken something. A build will usually include unit tests, so we can catch broken logic as well as code that plain won’t compile. In the Java world, there are a couple of contenders for CI frameworks, CruiseControl and Anthill. I reckon CruiseControl is a far superior product, and here I want to outline why.

CruiseControl is probably the oldest framework for CI in Java, having been around for a few years now. It’s Open Source, hosted on SourceForge, and developed and supported by people including a bunch of ThoughtWorkers. I work for ThoughtWorks – it’s probably worth stating that clearly here. Anthill is a newer product, and comes in an Open Source GPL version and a “pro” for-money version. Here I’ll be discussing Anthill Pro, which we’re using on my current project.

The argument I hear most often for using Anthill instead of Cruise is because it’s easier to set up. Simply drop a War into a web container and configure using fancy GUI screens. Cruise requires that you build it from source, and configure it using an XML file, but it’s a well documented process and really gives you lots of power to control how Cruise runs. With Anthill, you’re stuck with a (buggy) GUI.

A CI framework runs builds for you, whenever the code in source control changes. CruiseControl includes a “build loop” that continually polls source control for changes, and launches a build when it detects a developer has checked something in. If changes occur during a build, Cruise will realise as soon as the current build is finished, and launch another build straight away. By contrast, Anthill includes a “build scheduler”, in which you can run your build, say, every 15 minutes. The immediate drawback is that it might be several minutes from a change going into source control until Anthill runs the build – in Agile software development faster feedback is better so the Cruise model wins. You might think scheduling a build more often will help, but Anthill tends to get its knickers in a twist when it has lots of stuff in the queue. Schedule a build once a minute and you’ll quickly end up with a long queue, since Anthill isn’t smart enough to realise a build is already scheduled. The trick is to schedule builds at about the same frequency as your build time, so a build will be scheduled soon after each build completes. Unfortunately, Anthill will only let you choose certain scheduling intervals, so if your build takes 20 minutes you’re forced to use a half-hour schedule.

Multiple project support is included in both Cruise and Anthill. In Cruise, each project runs in its own thread, detecting changes and running builds in parallel when projects change. This works great, as long as you don’t try to run too many projects on the same machine (or you’re willing to live with the occasional long build). With Anthill, scheduling multiple projects means they end up in the build queue together, with build threads taking items off the queue and running builds. Unfortunately, there isn’t any way to prevent the same project from being run twice at the same time. If a project is built by two threads, it’s almost certain that the two builds will interfere with each other and fail.

Constant feedback from your build box is required if developers are to act quickly and fix broken builds. Cruise includes various publishers to send email and create a simple, single page website including build status, what changes have been made since the last build, and what tests (if any) are failing. You can also get a system tray application that shows a little green light when the build is good, and goes red and plays a Homer “Doh!” if the build is broken. By contrast, the Anthill emailer doesn’t even reliably send “success” messages when a broken build gets fixed. The web site it generates shows only basic build status – to find out what’s broken we have to produce our own JUnit report page, which is several clicks away from the main page. Similarly the “what’s changed” information is in Anthill’s revisions log, buried 3 clicks deep.

Overall I’ve been disappointed by my experience with Anthill Pro. It looks good at first sight, but for use on anything other than a toy project it just doesn’t cut it. Our current installation has a memory leak, and requires regular restarts so it’ll continue to send status emails. The Anthill Pro developers are apparently “working on it”. I really think the effort spent trying to get Anthill to work would have been better spent building and configuring CruiseControl. The time invested is well worth it, and you get all the benefits of a proper Open Source product.

Posted 00:44, 12 Aug 2004.  

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