max_lease

max_lease is how long the client keeps extending the lease of one unsettled delivery, an hour by default, and the budget of retry_after.

After a delivery has been held this long, the client stops extending its lease. The lease then runs out, and Pub/Sub redelivers the message, possibly to another consumer. A handler that may run longer than an hour needs a longer lease.

retry_after(delay) holds the delivery in the process for the delay, under this same lease. A delay longer than max_lease is refused with PubSubError::DelayBeyondLease, and the delivery comes back at once. The refusal keeps the delivery from coming back before the delay is over, from a lease that ran out.

Example

An invoice that is not ready comes back in ninety minutes, inside a lease of two hours. The tests advance the clock past the ninety minutes, and show that a delay of three hours comes back at once.

Macros

examples/pubsub_subscriptions_flow.rs

/// An invoice that is not ready comes back in ninety minutes, inside a lease of two hours.
#[subscriber(
    GooglePubSub::new("flow-invoices-workers")
        .create_with_topic("flow-invoices")
        .max_lease(Duration::from_hours(2))
)]
async fn send(invoice: &Invoice) -> HandlerOutcome {
    if !invoice.ready {
        return HandlerOutcome::retry_after(NOT_READY);
    }
    tracing::info!(invoice.id, "invoice sent");
    HandlerOutcome::ack()
}

Manual

examples/manual/pubsub_subscriptions_flow.rs

/// An invoice that is not ready comes back in ninety minutes, inside a lease of two hours.
struct Send;

impl Handle<Invoice> for Send {
    fn handle(
        &self,
        invoice: &Invoice,
        _outs: &(),
        _ctx: &mut Context<'_>,
    ) -> impl Future<Output = Result<(), HandlerOutcome>> {
        if !invoice.ready {
            return ready(Err(HandlerOutcome::retry_after(NOT_READY)));
        }
        tracing::info!(invoice.id, "invoice sent");
        ready(Ok(()))
    }
}

fn invoices() -> GooglePubSub {
    GooglePubSub::new("flow-invoices-workers")
        .create_with_topic("flow-invoices")
        .max_lease(Duration::from_hours(2))
}