Tarearbol.DynamicManager.handle_state_change

You're seeing just the callback handle_state_change, go back to Tarearbol.DynamicManager module for more information.
Link to this callback

handle_state_change(state)

View Source (since 0.9.0)

Specs

handle_state_change(state :: :down | :up | :starting | :unknown) ::
  :ok | :restart

Declares an instance-wide callback to report state; if the startup process takes a while, it’d be run in handle_continue/2 and this function will be called after it finishes so that the application might start using it.

If the application is not interested in receiving state updates, e. g. when all it needs from runners is a side effect, there is a default implementation that does nothing.