One of the points I make in my Feature Toggles talk is that you shouldn’t be querying a toggle’s status all over your codebase. Ideally, each toggle gets checked in as few places as possible - preferably only one place. The advantage of doing this is that very little of your codebase needs to be coupled to the toggles (either the toggle itself or the library/system for managing toggles itself)....
Recently, I was asked if I could provide an example of Branch By Abstraction when dealing with feature toggles. As this has come up a few times, I thought a blog post would be a good idea so I can refer others to it later too. The Context As usual, this is some kind of backend (micro)service, and it will send email messages somehow. We will start with two implementations of message sending: the “current” version; which is synchronous, and a “new” version; which is async....
While I was developing my Crispin project, I ended up needing to create a bunch of implementations of a single interface, and then use all those implementations at once (for metrics logging). The interface looks like so: public interface IStatisticsWriter { Task WriteCount(string format, params object[] parameters); } And we have a few implementations already: LoggingStatisticsWriter - writes to an ILogger instance StatsdStatisticsWriter - pushes metrics to StatsD InternalStatisticsWriter - aggregates metrics for exposing via Crispin’s api To make all of these be used together, I created a fourth implementation, called CompositeStatisticsWriter (a name I made up, but apparently matches the Gang of Four definition of a composite!...
This article has been updated after feedback from .Net Junkie (Godfather of SimpleInjector). I now have a working SimpleInjector implementation of this, and am very appreciative of him for taking the time to help me :) Serilog is one of the main set of libraries I use on a regular basis, and while it is great at logging, it does cause something in our codebase that I am less happy about....