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upgrade-kubernetes.md

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Upgrading Kubernetes

Constellation is a Kubernetes distribution. As such, dependencies on Kubernetes versions exist in multiple places:

  • The desired Kubernetes version deployed by kubeadm init
  • Kubernetes resources (deployments made while initializing Kubernetes, including the cloud-controller-manager, cluster-autoscaler and more)
  • Kubernetes go dependencies for the bootstrapper code

Understand what has changed

Before adding support for a new Kubernetes version, it is a very good idea to read the release notes and to identify breaking changes.

Upgrading Kubernetes resources

Everything related to Kubernetes versions is tracked in the versions file. Add a new ValidK8sVersion and fill out the VersionConfigs entry for that version. During cluster initialization, multiple Kubernetes resources are deployed. Some of these should be upgraded with Kubernetes. You can check available version tags for container images using the container registry tags API:

curl -qL https://registry.k8s.io/v2/autoscaling/cluster-autoscaler/tags/list | jq .tags
curl -qL https://registry.k8s.io/v2/cloud-controller-manager/tags/list | jq .tags
curl -qL https://registry.k8s.io/v2/provider-aws/cloud-controller-manager/tags/list | jq .tags
curl -qL https://mcr.microsoft.com/v2/oss/kubernetes/azure-cloud-controller-manager/tags/list | jq .tags
curl -qL https://mcr.microsoft.com/v2/oss/kubernetes/azure-cloud-node-manager/tags/list | jq .tags
# [...]

Normally renovate will handle the upgrading of Kubernetes dependencies.

Test the new Kubernetes version

  • Setup a Constellation cluster using the new image with the new bootstrapper binary and check if Kubernetes is deployed successfully.

    # should print the new k8s version for every node
kubectl get nodes -o wide
# read the logs for pods deployed in the kube-system namespace and ensure they are healthy
kubectl -n kube-system get pods
kubectl -n kube-system logs [...]
kubectl -n kube-system describe pods

  • Read the logs of the main Kubernetes components by getting a shell on the nodes and scan for errors / deprecation warnings:

    journalctl -u kubelet
journalctl -u containerd

  • Conduct e2e tests