Enum Advance 

pub enum Advance<A> {
    Next(A),
    Park {
        state: A,
        wake_after: Option<Duration>,
        error: Option<AdvanceError>,
    },
    Done,
    Failed(Error),
}

Outcome of one WalletAction::advance call.

The executor uses these to decide whether to persist, loop, schedule a wake-up or remove the checkpoint.

Variants

Next(A)

Transition to a new state. Executor persists state and calls advance on it.

Park

Pause until something external (notification, periodic sync) or wake_after (when set) re-drives the action. Executor persists state and returns.

wake_after is a hint, not a guarantee: it lives only in this process and is lost across restarts. advance MUST tolerate being called before the hint has elapsed.

error is the error that caused the park, if any.

Fields

state: A

wake_after: Option<Duration>

error: Option<AdvanceError>

Done

Terminal: executor removes the checkpoint row. Any permanent fact the action wants to retain (e.g. an “invoice paid” record) must be written to its own table before returning Done.

Failed(Error)

Terminal: executor removes the checkpoint row because of a fatal error. This advance should only be returned when no server change occured yet or when process has checked server status is expected one and it is safe to remove checkpoint