Rails does not fire my after_commit callback

Hello I have a peculiar problem. I use an after_commit callback to send notifications, but it seems the callback is not triggered at all. Simplified the situation looks like this:

class Message < ActiveRecord::Base
  after_commit :do_something

  def do_something
    raise 'Doing something'
  end
end

Then I expected to see the raise when I open the console and create a message. But nothing happens. Furthermore rails does not even complain if I delete the 'do_something' method completely. Note that this is not a test with transactional fixtures. I even see the record committed in the db. My rails version is 3.0.9. Thanks for any help especially if it's good :-)

Edit: I learned later that the callback DID get triggered when I deployed the code to a different machine. So it must be something with my setup. Still I would appreciate your insight about what could be causing this.

Edit2: From the comments.

The DB is MySQL so transactions are present.
Specifying the action of the callback did not help (:on => :create).
I need after_commit and no other callback

Solution

David mentioned the explanation for this behavior in the questions comment.

Transaction Callbacks documentation

"If any exceptions are raised within one of these callbacks, they will be ignored so that they don't interfere with the other callbacks. As such, if your callback code could raise an exception, you'll need to rescue it and handle it appropriately within the callback."