A declined card

Make the bank slow, watch the first payment time out, and see the retry turn it into a paid order.

At 21:03 the real order #4711 was declined: the bank's fraud check timed out during its nightly batch. Here you make the fake bank just as slow.

1Make the bank slow#

curl -X POST localhost:8081/admin/latency -d '{"ms": 25000}'

The fake bank now takes 25 seconds to answer, longer than the 15 seconds the payment service waits.

2Read the retry#

This is the part of the payment service that saves the order, in the three languages the lab ships. Pick yours; the choice sticks on every page.

var key = order.id();
var result = bank.authorize(card, amount, key);
if (result.isTimeout()) {
    Thread.sleep(Duration.ofSeconds(30));
    result = bank.authorize(card, amount, key);
}
return result;

key = order.id
result = bank.authorize(card, amount, key)
if result.is_timeout:
    time.sleep(30)
    result = bank.authorize(card, amount, key)
return result

key := o.ID
res, err := bank.Authorize(ctx, card, amount, key)
if errors.Is(err, ErrTimeout) {
	time.Sleep(30 * time.Second)
	res, err = bank.Authorize(ctx, card, amount, key)
}
return res, err

The same key goes with both calls, so the bank cannot charge the card twice.

3Pay and wait#

time curl -X POST localhost:8082/orders/4711/pay

{"order": 4711, "status": "paid", "attempts": 2, "elapsed_ms": 30412}
real    0m30.4s

The tracking page showed Still checking your payment for thirty seconds, then turned the payment tile green.

This is how the talk tells the same moment:

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