Kubernetes 1.16 releases with Endpoint Slices, general availability of Custom Resources, and other enhancements

Yesterday, the Kubernetes team announced the availability of Kubernetes 1.16, which consists of 31 enhancements: 8 moving to stable, 8 is beta, and 15 in alpha. This release contains a new feature called Endpoint Slices in alpha to be used as a scalable alternative to Endpoint resources.

Kubernetes 1.16 also contains major enhancements like custom resources, overhauled metrics and volume extension. It also brings additional improvements like the general availability of custom resources and more. Extensions like extensions/v1beta1, apps/v1beta1, and apps/v1beta2 APIs are deprecated in this version.

This is Kubernetes' third release this year. The previous version Kubernetes 1.15 released three months ago. It accorded features like extensibility around core Kubernetes APIs and cluster lifecycle stability and usability improvements.

Introducing Endpoint Slices in Kubernetes 1.16

The main goal of Endpoint Slices is to increase the scalability for Kubernetes Services. With the existing Endpoints, a single resource had to include all the network endpoints making the corresponding Endpoints resources large and costly. Also, when an Endpoints resource is updated, all the pieces of code watching the Endpoints required a full copy of the resource. This became a tedious process when dealing with a big cluster.

With Endpoint Slices, the network endpoints for a Service are split into multiple resources by decreasing the amount of data required for updates. The Endpoint Slices are restricted to 100 endpoints each, by default. The other goal of Endpoint Slices is to provide extensible and useful resources for a variety of implementations. Endpoint Slices will also provide flexibility for address types. The blog post states, “An initial use case for multiple addresses would be to support dual stack endpoints with both IPv4 and IPv6 addresses.” As the feature is available in alpha only, it is not enabled by default in Kubernetes 1.16.

Major enhancements in Kubernetes 1.16

General availability of Custom Resources

With Kubernetes 1.16, CustomResourceDefinition (CRDs) is generally available, with apiextensions.k8s.io/v1, as it contains the integration of API evolution in Kubernetes. CRDs were previously available in beta. It is widely used as a Kubernetes extensibility mechanism.

In the CRD.v1, the API evolution has a ‘defaulting’ support by default. When defaulting is combined with the CRD conversion mechanism, it will be possible to build stable APIs over time.

The blog post adds, “Updates to the CRD API won’t end here. We have ideas for features like arbitrary subresources, API group migration, and maybe a more efficient serialization protocol, but the changes from here are expected to be optional and complementary in nature to what’s already here in the GA API.”

Overhauled metrics

In the earlier versions, the global metrics registry was extensively used by the Kubernetes to register exposed metrics. In this latest version, the metrics registry has been implemented, thus making the Kubernetes metrics more stable and transparent.

Volume Extension

This release contains many enhancements to volumes and volume modifications. The volume resizing support in (Container Storage Interface) CSI specs has moved to beta, allowing the CSI spec volume plugin to be resizable.