Kubernetes 1.16 Highlights: Custom Resources, Metrics Overhaul, and Endpoint Slices

Release Overview

Kubernetes v1.16 was released on 18 September 2019. It is the third major release of 2019 and introduces 31 enhancements: eight promoted to stable, eight to beta, and fifteen remain in alpha.

Custom Resource Definitions Reach GA

CRDs are now served through apiextensions.k8s.io/v1 and are marked General Availability (GA). The GA release enforces stricter validation, defaulting, and structural schema requirements, which improves data‑consistency for API clients and simplifies version‑migration strategies.

Metrics Overhaul

The historic global metrics registry has been replaced by a per‑component registration mechanism. Metrics are now registered through the k8s.io/component-base/metrics package, giving each component its own stability guarantees and making observability more predictable.

Volume Extensions

CSI volume‑resize support graduates to beta, allowing any CSI driver that implements the resize RPC to expand PersistentVolumes without recreating them. This change reduces downtime for stateful workloads.

Windows Enhancements

Beta: Active Directory Group Managed Service Accounts (GMSA) are now supported, providing automatic password rotation and simplified Service Principal Name (SPN) handling for Windows containers that need to access external resources.

Alpha: The RunAsUserName field is added to WindowsSecurityContextOptions, enabling the specification of a Windows identity (username) under which a container runs.

Alpha: kubeadm gains commands to add or reset Windows worker nodes using the same workflow as Linux nodes, streamlining mixed‑OS cluster provisioning.

Alpha: CSI plugins for Windows are introduced, allowing Windows nodes to consume persistent storage via the CSI driver model.

Endpoint Slices

Endpoint Slices are an alpha feature that replace the monolithic Endpoints object. A service’s endpoints are partitioned into multiple slice objects (default up to 100 endpoints per slice). This reduces the amount of data transferred during updates dramatically; for example, in a 5 000‑node cluster with a 1 MiB endpoint object, a full update would generate ~5 GiB of traffic, whereas slices reduce the traffic to roughly 2 % of that volume.

Slices also carry topology information (region, zone) and support dual‑stack address lists (IPv4 + IPv6).

Other Notable Updates

Topology Manager: a new Kubelet component that coordinates CPU, memory, and device allocation to improve pod placement based on hardware topology.

IPv4/IPv6 dual‑stack: Pods and Services can now be assigned both IPv4 and IPv6 addresses, enabling gradual migration to IPv6.

Cloud Controller Manager migration: provides more flexible options for cloud‑specific controller implementations.

API deprecations: the extensions/v1beta1, apps/v1beta1, and apps/v1beta2 APIs are removed.

For the complete list of changes, see the official Kubernetes blog post: https://kubernetes.io/blog/2019/09/18/kubernetes-1-16-release-announcement/