How do recurring payments actually work?

[artfulrobot.com]

Hi.

I'm interested in using Stripe for recurring payments but I can't find anything that explains how recurring payments are processed by CiviCRM.

There's http://book.civicrm.org/user/current/contributions/payment-processors/ which has a sentence saying it exists as a possibility for some processors. Then there's lots of people re-thinking how it works e.g. https://civicrm.org/blogs/sarahgladstone/rethinking-automated-recurring-contributions-code-attached and https://civicrm.org/blogs/sarahgladstone/rethinking-automated-recurring-contributions-code-attached

But I've not found anything about the mechanics of how it currently works. Can anyone signpost me, or give a summary here? I'm looking for a flowchart type thing, showing which data gets sent where and when; how systems talk to each other; how payments are recorded in CiviCRM at each stage etc.

Thanks.

[SarahG (FountainTribe)]

I am not aware of any documentation on how CiviCRM core processes recurring contributions for Authorize.net or PayPalPro (ie the only payment  processors that offer recurring, that are also part of core.)

You can look at the code for Authorize.net at:
civicrm/extern/authorizeIPN.php

Or PayPalPro:
civicrm/extern/ipn.php

The other payment processor that offers recurring is iATs. ( https://civicrm.org/extensions/iats-payments )

The developers that work on the iATS extension (and I) have been talking about that all payment processor logic should be removed from core, and should only be in extensions.  I have also created an extension that should help any developer add recurring contribution support to their processor. See: https://civicrm.org/extensions/payment-processor-helper   

(My extension overrides the core handling logic of recurring contributions from PayPalPro and Authorize.net )

If you are planning on enhancing the Stripe payment processor to handle recurring, I would be happy to update my extension for Stripe.