If you are the kind of person who cares about whether the validation closes the IPN retry so you can come up with a reasonable strategy for handling your database transaction policy (which is a good thing: people should care this much about everything they do), then Stripe's documented policy should be a non-starter, as it seems to indicate there is not going to be any retry at all if the request in any way hits your server: "Stripe ensures that webhooks are sent successfully but does not attempt to re-send webhooks that return errors in the response."
WePay's retry policy at least exists, but only retrying three times total, with those three times only spanning a single hour of attempts, is kind of bothersome... I have totally had outages that affected some random load balancer for an hour in the middle of the night: PayPal will retry for something like four days, and has a mechanism to "force flush" the notifications as your infrastructure comes back online.
Honestly, all of these APIs are not that great. Amazon's API, for example, does not let you get the shipping address. They return it as part of the co-branded UI return, but that request to your server, at scale, will sometimes be lost in transit. When the user goes back through the payment process, you are encouraged to look up the existing token the user succeeded in authorizing by CallerReference and then continuing the payment, but that means the shipping address is not sent, and you can't query for it. You can, however, get it via IPN, but if you find some silly bug in your code that drops an IPN's incoming shipping address (but returns a successful result), you are simply screwed and have to talk to the customer to recover the shipping address for that transaction.
Looking more at WePay, I again see the same thing I keep harping about regarding Stripe: I see no mentions of chargebacks. Doing a "site:wepay.com chargeback" search using Google I find their terms of service, but nothing in their API documentation; and omg: their terms of service regarding chargebacks is the worst I have so far seen... $35 ding and your account seems to immediately be put on hold and goes into account review? For a single chargeback? WTF.
Hey Saurik, Just wanted to say that we're aware of the (significant) flaws in the webhook APIs. We're in the process of redesigning them now, so thanks for the feedback on what is important to you.
(Also, just FYI, you can see logs of all the webhooks in your Stripe account, including the response body and response status code, and they can be retried with a button click -- a manual process, yes, but it is at least possible)
WePay's retry policy at least exists, but only retrying three times total, with those three times only spanning a single hour of attempts, is kind of bothersome... I have totally had outages that affected some random load balancer for an hour in the middle of the night: PayPal will retry for something like four days, and has a mechanism to "force flush" the notifications as your infrastructure comes back online.
Honestly, all of these APIs are not that great. Amazon's API, for example, does not let you get the shipping address. They return it as part of the co-branded UI return, but that request to your server, at scale, will sometimes be lost in transit. When the user goes back through the payment process, you are encouraged to look up the existing token the user succeeded in authorizing by CallerReference and then continuing the payment, but that means the shipping address is not sent, and you can't query for it. You can, however, get it via IPN, but if you find some silly bug in your code that drops an IPN's incoming shipping address (but returns a successful result), you are simply screwed and have to talk to the customer to recover the shipping address for that transaction.
Looking more at WePay, I again see the same thing I keep harping about regarding Stripe: I see no mentions of chargebacks. Doing a "site:wepay.com chargeback" search using Google I find their terms of service, but nothing in their API documentation; and omg: their terms of service regarding chargebacks is the worst I have so far seen... $35 ding and your account seems to immediately be put on hold and goes into account review? For a single chargeback? WTF.