@callback actions() :: :all | [atom()]

Returns the actions this hook is expected to listen on.

This will default to an empty list, to force the developer to opt into the actions they receive notifications for. If all actions should be received, you can use the :all atom to receive everything.

@callback async?() :: boolean()

Returns whether this hook is asynchronous or not.

@callback handle_notify(
  action :: {action :: atom(), args :: list()},
  result :: {status :: atom(), value :: any()},
  state :: any()
) :: {:ok, any()}

Handles a cache notification.

The first argument is the action being taken along with arguments, with the second argument being the results of the action (this can be nil for hooks) which fire before the action is executed.

@callback timeout() :: nil | integer()

Returns the timeout for all calls to this hook.

This will be applied to hooks regardless of whether they're synchronous or not; a behaviour change which shipped in v3.0 initially.

@callback type() :: :pre | :post | :service

Returns the type of this hook.

This should return :post to fire after a cache action has occurred, and return :pre if it should fire before the action occurs. The :quiet type is for hooks which don't listen to any broadcasts.