May 19, 2017

...Learn TDD with Codemanship

20 Dev Metrics - 18. External Dependencies

18th in my series 20 Dev Metrics is External Dependencies.

If our code relies too much on other people's APIs, we can end up wasting a lot of time fixing things that are broken when the contracts change. (Anyone who's written code that consumes the Facebook API will probably know exactly what I mean.)

In an ideal world, APIs would remain backwards-compatible. But in the real world, where 3rd-party developers aren't as disciplined as we are, they change all the time. So our code has to keep changing to continue to work.

I would argue that, with the way our tools have evolved, it's too easy these days to add external dependencies to our software.

It helps to be aware of the burden we're creating as we suck in each new library or web service, lest we fall prey to the error of buying the whole Mercedes just for the cigarette lighter.

The simplest metric is just to count the number of dependencies. The more there are, the more unstable our code will become.

It's also worth knowing how much of our code has direct dependencies on external APIs. Maybe we only depend on JDBC, but if 50% of our code directly references JDBC interfaces, we still have a problem.

You should aim to have as little of your code directly depend on 3rd-party APIs as possible, and as few different APIs as you can use to build the software you need to.

(And, yes, I'm including GUI frameworks etc in my definition of "external dependencies")

Posted 1 year, 4 months ago on May 19, 2017