Comment 1 for bug 1858002

Hey Drew, thanks for the report.

What prevents this is kubernetes-master's get_dns_provider function[1] that takes dns-provider=auto to mean "keep using the existing provider," even if it was 'none'. When you go from 'none' to 'auto', it will keep using 'none'. It's by design, but it's not an intuitive design, and could use improvement.

> However, this did not trigger re-deployment of core-dns, though that was the dns-provider configuration found in /var/snap/cdk-addons/current/dns-provider file. I think the apply function is not run upon changing of this variable, but maybe only during deployment and charm/k8s version upgrade.

The kubernetes-master leader unit reconfigures cdk-addons and runs cdk-addons.apply on every hook: config-changed, update-status, etc. I don't think that's likely to be an issue here.

I am confused how you could have a value of 'core-dns' in /var/snap/cdk-addons/current/dns-provider after changing dns-provider from 'none' to 'auto'. Given the get_dns_provider function I described above, it should stay 'none'. Can you confirm that you see that on the kubernetes-master leader unit and not one of the followers?

[1]: https://github.com/charmed-kubernetes/charm-kubernetes-master/blob/daa8e11d70adb92e46853229ed88c57f4eeafc21/reactive/kubernetes_master.py#L2618-L2641