I thought about this, and it can't really get any worse than 'total outage', so I thought it was worth taking a shot. It can't go any more down.
It worked for me, so once Heroku has sorted their s*t out and their DNS system is back up it's just a matter of deleting the A records and replacing it with the CName.
Worst case scenario is the underlying Amazon IP Addresses change and it goes back down.
Wouldn't the worst case be the underlying IP address changes, and your site now points to some other service? Since Heroku doesn't offer static IPs, I don't think.
Heroku seems to use the Host header on the HTTP request to determine what customer the request is sent to, so I don't think it can end up somewhere it shouldn't be unless the IP leaves control of Heroku entirely and is picked up by another AWS customer.
Re:Issues with upstream DNS provider
by rsweeney21 on Tuesday August 23, 2022 @08:25PM
(#32573475)
Heroku uses the host name to route requests. So you wouldn't serve another site, it would just give you an error that your site wasn't found or something.
Re:Issues with upstream DNS provider
by exitnode_ttl0 on Tuesday August 23, 2022 @08:21PM
(#32573438)
There is one more problem I can think of (but yes you're right, it can't get worse than 'total outage'): Heroku might detect that the CNAME is missing and will deactivate some stuff from their automatic domain management / TLS certificate issuing.
What are the chances that their current work on the DNS issues might replace the underlying IP-addresses and hence we are making it harder on ourselves?