Umbrella sub project config issue

If you treat your utility app like a 3rd party library, you can follow the advice here: https://michal.muskala.eu/post/configuring-elixir-libraries/

If the KVServer should get it’s configuration from another OTP app config, you probably need a mixin module like Ecto.Repo that is used to configure it:

defmodule MyApp.KVServer
  use KVServer, otp_app: :my_app

end

This helper app should be unaware of the app whatever parent app is using this app. So I think {:bar, in_umbrella: true} doesn’t fit in this situation. and how do I get the config in the sub app like
Application.get_env(:parent_app, KVServer)[:secret_key] how do I know the parent app name

You need to include a reference to apps you want to access in your mix.exs

Example:

App 1: foo
App 2: bar
App 3: baz

foo wants access bar. bar does not have any dependencies on foo, which would cause a circular dependency issue.

So in foo, reference bar as follows:

      {:bar, in_umbrella: true}