Today I implemented the module “ConfigLogger” for Exconfig. Exconfig is a configuration cache for Elixir and can be used to read environment vars during runtime.

require Exconfig

value = Exconfig.get(:env, :conf_key, "Default Value")

get/3 now is a macro and records it’s usage to configuration.log during compile time, in all environments but :prod.

In other environments than :prod the first usage of the macro starts a GenServer (Exconfig.ConfigLogger) and adds every use of get/3 to its state.

Example

  require Exconfig
  value = Exconfig.get(:env, :my_key, "My Value")

Will write the following line to configuration.log

MY_KEY="My Value"

Do you know what might be configurable in your app?

I use Exconfig.get(:env,...) a lot and to be honest, I can’t remember what is configurable. Neither I have the discipline to add every new key of my configuration to the documentation immediately.

That’s where ConfigLogger can help. After compiling the application, you can find configuration.log in your project directory. So, you have a template for a shell script, that can be edited and used to set up the environment before starting the app. Also, no single configuration can be overseen.