@Override
    public void stop() {
        super.stop();
        // Remove this module as a user event listener
        UserEventDispatcher.removeListener(this);
        //stop timer if started
        cancelTimer();
    }
Returns the approximate size (in bytes) of the XML messages stored for all
users.

@return the approximate size of all stored messages (in bytes).
xmppserver/src/main/java/org/jivesoftware/openfire/OfflineMessageStore.java