Kubernetes cleans house, bins legacy kube-dns, IPVS, and cgroup v1

The latest Kubernetes v1.37 release, named after India's lush Himalayan region of Uttarakhand, demonstrates the open-source orchestrator's focus on production readiness. The update, which includes 67 changes - 16 stable features, 23 beta features, 27 alpha features, and one deprecated item - aims to streamline the user experience and retire outdated elements.

CNCF, the organization overseeing Kubernetes among over 220 cloud-native projects, has to balance its user base's desire for the latest features with the need for stability. Approximately 82% of container users now run Kubernetes in production, up from 66% in 2023, and the platform is a key driver for AI workloads, with 66% of organizations hosting generative AI models using Kubernetes.

One significant change is the promotion of the Metrics API to general availability after nine years in beta. This API, which provides CPU and memory usage for pods and nodes, has proven its reliability in production environments and will now be officially recognized as stable. The Metrics API was able to sidestep the mandatory three-releases rule by being an out-of-tree aggregated API rather than one managed directly by the API server.

The release also marks the end of an era for kube-dns, the original built-in DNS server. It will be replaced by CoreDNS, the default cluster DNS add-on since Kubernetes v1.13. Kubernetes will retire kube-dns before Kubernetes 1.40, and clusters running kube-dns will stop working after that version. Additionally, kube-proxy, which handles routing among pods, will no longer support the Linux IPVS load balancer software beginning with Kubernetes 1.43.

Instead, nftables will be the way forward. Furthermore, the first version of Linux control groups (cgroup v1), used for grouping server processes for easier management, will also be phased out in favor of cgroup v2, which offers more granular oversight of container resources.