The example is flawed -- if there is an exception incurred before or during the sending of the email, the operation will be erroneously marked as "cancelled" without having completed all of the cancellation flow. Namely, with the example as given, it is possible to have a cancelled order for which an email has not been sent out.
Moving the second line (the one that changes the status to "cancelled") to the end fixes this issue, though it does not implement "exactly once" semantics for the sending of the email. If "exactly once" is desirable, then additional logic is required. But in every case, the example as given is incorrect.
Moving the second line (the one that changes the status to "cancelled") to the end fixes this issue, though it does not implement "exactly once" semantics for the sending of the email. If "exactly once" is desirable, then additional logic is required. But in every case, the example as given is incorrect.