The Observer tool we already used in a couple of recipes throughout the book allows us to have a better insight on supervision trees and to have information on the processes. It also allows us to "kill" a process and watch it be replaced by another one!
To start inspecting our supervisors and processes, we will follow these steps:
Open a new IEx session:
> iex
Start the Observer tool:
iex(1)> :observer.start
Select the Applications tab in the graphical interface.
In the logger application info, right-click on Elixir.Logger.Watcher and select the Kill process option, and then confirm the option in the popup.
Take a look at the PIDs for some processes. They have changed! This means that
Elixir.Logger.Supervisor
restarted some processes when one of its supervised processes terminated.