Per https://github.com/kubernetes/community/blob/master/contributors/design-proposals/release/versioning.md
v1.15 is going to fall off patch support soon. We need to upgrade to v1.16 soon.
There will be several subtasks for this because to do the upgrade we need to fix up webservice, a mistakened use of a deprecated API in maintain-kubeusers and likely other things.
This will start support for ipv6, but support for ipv6 will be far better in 1.18 (now released).
[x] Update maintain-kubeusers to use the policy apiGroup instead of extensions
[] Replace pykube in webservice
[] Script the process for upgrading a worker node because doing it 50+ times by hand sounds bad.
[] Stage packages on our mirror repo for the current patch release of 1.16
[] Install kubectl and kubeadm first in `toolsbeta` to validate that they work correctly with the 1.15 cluster.
[] Follow the procedure in https://v1-16.docs.kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/ to upgrade `toolsbeta`
- This implies upgrading the control plane nodes by draining them one at a time and upgrading. kubelet is a package upgrade, the rest is kubeadm
- When the control plane is fully upgraded, then the worker nodes get upgraded, again draining them, upgrade kubeadm, run the upgrade, then upgrade kubelet. The procedure is very detailed in the doc.
[] Upgrade tools after announcements
[] Refresh all external certs (Prometheus, admission controllers)