How often has someone come up to you and asked you what build of your software is currently deployed in a specific environment?
How many times have you come across a .jar or .dll file and wondered what version it is? Especially when using Open Source Software?
The most frightening one for me is when I’ve looked at a cluster of production servers and noticed that the .war file for the application deployed on it is a different size on one of the nodes. Which one was the correct one to deploy? Luckily this happened to me a long time ago, but I know that people out there are still having this problem today.
The solution is what I call “Self Identifying Software”. Every build of your software needs to have something that tells you what version it is and how to get back to the source code that created it. Having a build label or release number visible in your application is a good start, but it does not make your software Self Identifying. Product companies have been doing this for ever. The problem is that for that number to be useful (particularly when you’re trying to access the source code to reproduce and fix a bug) you then need to refer to a build system or release notes to find out where the source code came from (if you’re lucky). It often also does not apply to development builds. To be truly Self Identifying you need to make sure that every build (including builds developers create on their workstations) also includes enough information from the SCM system so that anyone who has access to the source code can go right back to the exact source code that produced that binary. For example, if you use Subversion as your SCM then this will be a URL and a revision number.
This is not exactly a new concept, it’s something I (and others) have been doing for a number of years now. The reason I’ve decided to write about it now though is that recently I was showing a new guy around one of the projects I’m working on at the moment, and when I showed him how to determine which version of the app was deployed he was delighted.