Set our own KUBERNETES_MIN_VERSION

[vdemeester]

The KUBERNETES_MIN_VERSION and knative.dev/pkg/version package are setting which minimum kubernetes version that is supported. If we try to run the controller on an older Kubernetes version, it will panic.

As of today, we inherit this value from knative version.go value. Any time we update the version of knative.dev/pkg this value can change — Knative updates it depending on Kubernetes maintenance support window — and thus we need to take this into account.

These updates are a bit arbitrary from the tektoncd/pipeline point of view as, most of the time, it would still work with older version of Kubernetes. We don't use that much API, most of it is super stable and doesn't change a lot, …

I am creating this issue to discuss if we want to set our own KUBERNETES_MIN_VERSION (and test accordingly) in tektoncd/pipeline.

• By default tektoncd/pipeline would be installable in a wider range of Kubernetes version (and thus distributions)
• We decide when we stop "supporting" a given kubernetes version.

cc @afrittoli @tektoncd/core-maintainers @tektoncd/core-collaborators

[afrittoli]

@vdemeester I've also had this thought on the back of my mind for some time.

Until now, the knative package update has driven this update, but I think it would be a very good idea to have our own, especially now that we have introduced k8s matrix testing.

Since we have a pretty stable release plan for Tekton LTS and k8s has a similar plan, we could probably schedule updates to the k8s min version along with the release plan.