Feature Flagging

As the lazy proactive engineer that I am, I tend to advocate for self-service tooling and the empowerment of decision-makers. The idea of continuous integration and continuous deployment (CI/CD) can be scary for some shops.

Usually the main concern is code that “goes for a ride” with a desired strategy. What happens when code isn’t quite ready for prime-time? Maybe product & marketing hasn’t announced a new feature or maybe there is a dependency that isn’t quite ready yet? Well part of the solution involves Feature Flagging. This is the idea that code can be deployed, then activated at a later point in time. This decouples deployment from functionality, making the change of behavior a configuration item.

In the past, I have seen a lot of home-grown solutions that tried to solve this problem. Today, it appears there is a growing number of solutions both commercial and open-source that fill this space.

My main recommendation is putting the tooling in the hands of the decision-maker and free up your engineering team to spend their time on more productive activities. Perhaps the decision-maker is a product owner?

A follow up recommendation is to consider the cost of a feature-flag. Generally-speaking a flag’s state is stored in a database? Is your code optimized to check the feature flag only when necessary, or does a page load trigger many external calls? Is the datastore right-sized? Does the network have enough throughput? This is an implementation detail that should be considered before jumping head-first into implementing feature flags.

During my morning scroll, I stumbled upon an open-source offering called Flagr. I like that there is an HTTP API for integration into a diverse set of tooling. I like that there is a GUI that can enable non-programmers to take feature roll-out into their own hands.

I have not used Flagr yet, so I am not 100% understanding of the short-comings of this tool. I do encourage that before you start working on writing your own flagging system to take a survey of offerings that can guide you into a pattern that you don’t have to dream up yourself.

Happy development! Cheers.

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