Lately, I had an irritating trouble in facebook (I think many people too). Some time, when I refresh my page, the comment status is different somehow. Sometime there’s even a notification of the comment that haven’t existed yet. It’s a bad bad thing facebook, and I believe the problem is surely complex (cos, if it is simple, it must have been solved by now 😀 ).
Well, I don’t know what is actually happening there, but I believe this is obviously synchronicity problem. Somehow, because of the distributed system size, the data updating on one server, wasn’t propagate fast enough to the other server. And the wrong turning here is because the existence of this scenario “There’s a time when I refresh my page, the server maybe full somehow and I am redirected to other server”. Now, the other server hasn’t had any update from my old server, and here come the inconsistencies.
The notification is somehow stable because it is maintained by smaller cluster of servers, but wall post suffered heavily by now (message sometime). It is ironic somehow, because facebook’s technology is very advanced, and yet, they can’t overcome this simple problem. Maybe someday Tanenbaum can propose the more sophisticates method for this thing 😦