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SCS K8S Version Policy

Introduction​

The Kubernetes project maintains multiple release versions including their patched versions. In the project, the three most recent minor releases are actively maintained, with a fourth version being in development. As soon as a new minor version is officially released, the oldest version is dropped out of the support period. Kubernetes supports its releases for around 14 months. 12 of these are the standard support period. The remaining 2 months are the end-of-life support period for things like:

  • CVEs (under the advisement of the Security Response Committee)
  • dependency issues (including base image updates)
  • critical core component issues

More information can be found under [Kubernetes Support Period].

The Kubernetes release cycle is set around 4 months, which usually results in about 3 minor releases per year.

Patches to these releases are provided monthly, except for the first patch, which is usually provided 1-2 weeks after the initial release (see Patch Release Cadence).

Motivation​

Kubernetes is a living, fast-paced project, which follows a pre-defined release cycle. This enables forward planning with regard to releases and patches, but also implies a necessity to upgrade to newer versions quickly, since these often include new features, important security updates or especially if a previous version falls out of the support period window.

We want to achieve an up-to-date policy, meaning that providers should be mostly in sync with the upstream and don't fall behind the official Kubernetes releases. This is achievable, since new versions are released periodical on a well communicated schedule, enabling providers and users to set up processes around it. Being up-to-date ensures that security issues and bugs are addressed and new features are made available when using SCS compliant clusters.

It is nevertheless important to at least support all Kubernetes versions that are still inside the support period, since users could depend on specific versions or may need longer to upgrade their workloads to a newer version.

The standard therefore should provide a version recency policy as well as a support window period.

Decision​

In order to keep up-to-date with the latest Kubernetes features, bug fixes and security improvements, the provided Kubernetes versions should be kept up-to-date with new upstream releases:

  • The latest minor version MUST be provided no later than 4 months after release.
  • The latest patch version MUST be provided no later than 1 week after release.
  • This time period MUST be even shorter for patches that fix critical CVEs. In this context, a critical CVE is a CVE with a CVSS base score >= 8 according to the CVSS version used in the original CVE record (e.g., CVSSv3.1). It is RECOMMENDED to provide a new patch version in a 2-day time period after their release.
  • New versions MUST be tested before being rolled out on productive infrastructure; at least the CNCF E2E tests should be passed beforehand.

At the same time, providers must support Kubernetes versions at least as long as the official sources as described in Kubernetes Support Period:

  • Kubernetes versions MUST be supported as long as the official sources support them according to the Kubernetes Support Period and their end-of-life date according to the Kubernetes Releases page.
  • It is RECOMMENDED to not support versions after this period in order to not encourage usage of out-of-date versions.

All documents regarding versioning, releases, etc. for the official Kubernetes projects can be found on the Kubernetes Releases page.

Conformance Tests​

The script k8s_version_policy.py requires a kubeconfig file with connection details for a set of existing Kubernetes clusters that should be checked, with each of these clusters representing one of the currently supported upstream Kubernetes releases. It will check the encountered cluster versions according to the rules of this standard. Rule violations will be reported on various logging channels: ERROR for mandatory rules and INFO for recommended rules. The script will exit with a non-zero status if a mandatory rule has been violated or if the test could not be performed.