Per https://wikitech.wikimedia.org/wiki/Operating_system_upgrade_policy, by mid 2020 we will begin the deprecation phase of Stretch, with a deadline for removal on early to mid 2021. This task is about identifying our various blockers and drafting a plan for the migration of our kubernetes infrastructure to buster
The major components are below. They are grouped in rather large groups, as there is little benefit in listing them one by one (e.g. kube-scheduler+kube-controller-manager etc).
We still haven't upgraded to newer calico versions. This is an unknown, we need to investigate/test more before we have a verdict on versions for this component.
That is the component that is expected to have the least possible friction. It's golang, statically built, easy to share between our wikimedia repos.
Buster comes with docker 18.09.1+dfsg1-7.1+deb10u1. We probably want to run extensive tests before widely using it. We 've been holding off from upgrading from our current docker version as it has caused no issues up to now.
buster comes with a newer kernel (4.19) that includes the patches listed at https://bugzilla.kernel.org/show_bug.cgi?id=198197 so that's great.
iptables in buster is 1.8.2, however we want to at least target 1.8.3 which is in buster-backports. The rationale of for that decision is based on https://github.com/kubernetes/kubernetes/issues/71305. However, https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/#ensure-iptables-tooling-does-not-use-the-nftables-backend way more clearly says to switch to iptables-legacy. Both should be evaluated.