Review the usage of deprecated APIs

[gcapizzi]

Kubernetes 1.22 will stop serving a few deprecated API versions. The affected APIs have all been promoted to v1 from v1beta1. A list is provided in the deprecation guide.

Also note that some of these v1 APIs were introduced as recently as v1.19, which means that by switching to them we would have to drop support for versions < v1.19. Let's figure out if this is the case for the APIs we use and establish the range of Kubernetes versions we can support.

[gcapizzi]

The only v1beta1 APIs that we are using are:

• policy/v1beta1.PodSecurityPolicy: this will be replaced by the PodSecurity admission controller, which is still in alpha, so no rush.
• policy/v1beta1.PodDisruptionBudget: this has been replaced by policy/v1.PodDisruptionBudget and will go away in v1.25. Some deprecations notes:
  • policy/v1.PodDisruptionBudget has been available since v1.21.
  • All existing PDBs are going to be accessible via the new API.
  • The only breaking change between the two versions is the behaviour of spec.selector when it's empty, which never seems to be the case in Eirini (see here and here).

So:

• we should work just fine in v1.22;
• we'll need to upgrade PSPs and PDBs before v1.25, possibly waiting for v1.21 to fall out of the maintenance window (which seems to be of three minor versions, so as soon as v1.24 is released).