I'm using the Notification XML API, and Google seems to be delivering notifications not in the order I expect. For example, an order-state-change
notification will have a new-financial-order-state
of CHARGING
after one immediately preceding it had already set it to CHARGED
.
It seems like the IPN serial-number
s are monotonically increasing, however, so perhaps I can use them to ignore notifications which arrive out of order? I don't see any documentation on whether that's something which will be future-proof.