[1]: https://docs.google.com/forms/d/e/1FAIpQLSetFLqcyPrnnrom2Kw8...
You do have to be a little careful, for example adding a new SAN to a cert might fail due to 20-per-domain-per-week limits, attempting to renew that cert without removing the extra SAN will fail.
> I could have avoided this by combining names into a single certificate
You can get a cert (via <=20, 100 SAN combined certs) 2000 subdomains per week.
I actually don't really understand your problem case though. What do you mean by:
> when moving domains
That entirely depends on where/how you're terminating TLS.
Do you really have > 20 different pieces of independent software all doing their own TLS?
This is exactly what things like HAProxy are for.
You deploy software, that software declares it needs TLS for its endpoint, and certs are obtained.
While moving from one cluster to another, a new deployment of everything was done - about 20 different services - a few minutes work with Kubernetes. However, the fetching of TLS certs stopped working for the very last service!
Yes, I should have migrated the certs, however, the migration was happing due to a failure - I couldn't access the old certs.
I now make sure to backup those secrets rather than rely on re-issuance.
Still, for a usecase like Kubernetes, 20 certs per domain per week is limiting. I do totally understand that the quotas are in place because cert issuance is expensive, but I'd happily pay a yearly subscription fee to LE to cover the costs and help fund them if the option was there!
Each independent application is isolated from each other, sharing a TLS cert/key among them all means we're weakening security - again, the Kubernetes patterns here would mean we need to duplicate the secret data into each applications namespace, allowing a compromise of one to compromise the TLS of all.
There are legitimate reasons to not share a single TLS cert for everything in an environment like Kubernetes.
(I'm nearly certain it's not possible to reference secrets cross namespace when declaring an ingress secret, or mounting a secret)
yeah, this would be wrong indeed.
Is there any requirement for an TLS terminating proxy acting as k8s ingress to actually store the TLS secrets in the same namespace where the requesting ingress object lives?
There may be ways around this, however, I've never personally looked for them.