April 21, 2017

...Learn TDD with Codemanship

20 Dev Metrics - 4. Feature Usage

The next few metrics in my 20 Dev Metrics Twitter series are going to help us understanding which parts of our code present the greatest risk for failure.

One metric that I'm always amazed to learn teams aren't collecting is Feature Usage. For a variety of reasons, it's useful to know which features of your software are used all the time and which features are used rarely (if ever).

When it comes to the quality of our code, feature usage is important because it guides our efforts towards things that matter more. It's one component of risk of failure that we need to know in order to effectively gauge how reliable any line of code (or method, or module, or component/service) needs to be. (We'll look at other components soon.)

Keeping logs of which features are being used is relatively straightforward; for a web application, your web server's logs might reveal that information (if the action being performed is revealed in the URL somehow). If you can't get them for free like that, though, adding usage logging needs some thought.

What you definitely don't want to do is add logging code willy-nilly all across your code. That way lies madness. Look for ways to encapsulate usage logging in a single part of the code. For example, for a desktop application, using the Command pattern offers an opportunity to start with a Command base class or template class that logs an action, then invokes the helper method that does the actual work. Logs can be stored in memory during the user's session and occasionally sent as a small batch to a shared data store if performance is a problem.

For a web application or web service, the Front Controller pattern can be used to implement logging before any work is done. (e.g., for an ASP.NET application, a custom logging HttpModule.) Whatever the architecture, there's usually a way.

And feature usage is good to know for other reasons, of course. Marketing and product management would be interested, for a start. We're all guessing at what will have value. As soon as we deliver working software that people are using, it's time to test our theories.

Posted 6 days, 10 hours ago on April 21, 2017