PayPal IPN - Can the IPN be trusted to trigger subscription start/end?

Question

Can subsc_signup be relied on for allowing pepole access to services at a site (subsc_eot for terminating, subsc_modify for modifying subscription levels) - i.e. can the IPN be trusted as a reliable service?

During the integration, while working on a sandbox account, I encounter problems of queued IPN messages. Paypal IPN messages are queued since yesterday where a subscrion message was delivered and a payment message 1 minuete later was queued. Since, and for the last 20 hours, all following messages are queued.

Trying to send an IPN message from the simulator works. Trying to resend an IPN message from list of already sent messages is succesful!

2 years ago - this was reported: Paypal IPN Status - Queued

Is this again a temporary problem at PayPal servers?

How often do such problems encountered?

Is it related to the fact that I am using a sandbox?

Answer 1

The queue issue seems to be strictly related to the sandbox. However, I wouldn't rely on the IPN to acivate your customers account too much as there's occasionally a delay in the notifications.

Here's how I handle subscriptions via paypal in my app: on post data to thank you page I set the account to activated, this is not secure on it's own however there's a second tier of activation that relies on a verified IPN message. Via the IPN after a verified notification, if the ping is "subscr_payment", after checks, the app sets an "active until" date for the user which is date of payment + subscription length. Upon login this date checked and account status is set accordingly, if account is activated but a active until date was never set(forged post data to the thank you page or the IPN server is down for longer than a session) it get's set back to inactive.

This kind of setup also works well for Stripe.