I've got some code like this that runs on a schedule.

`ping -c 1 -W 1 #{stack.ip}`
stack.update_attribute :online, $?.success?

If the value of the online attribute hasn't changed, nothing is saved to the database. This is the documented behavior and what I would expect. However, the after_save callback is still triggered in my observer even though no save operation technically occurred. Is this the correct behavior?