Introducing the Windows Operational Readiness Specification

Since Windows support graduated to stable with Kubernetes 1.14 in 2019, the capability to run Windows workloads has been much appreciated by the end user community. The level of and availability of Windows workload support has consistently been a major differentiator for Kubernetes distributions used by large enterprises. However, with more Windows workloads being migrated to Kubernetes and new Windows features being continuously released, it became challenging to test Windows worker nodes in an effective and standardized way.

The Kubernetes project values the ability to certify conformance without requiring a closed-source license for a certified distribution or service that has no intention of offering Windows.

Some notable examples brought to the attention of SIG Windows were:

  • An issue with load balancer source address ranges functionality not operating correctly on Windows nodes, detailed in a GitHub issue: kubernetes/kubernetes#120033.
  • Reports of functionality issues with Windows features, such as “GMSA not working with containerd, discussed in microsoft/Windows-Containers#44.
  • Challenges developing networking policy tests that could objectively evaluate Container Network Interface (CNI) plugins across different operating system configurations, as discussed in kubernetes/kubernetes#97751.

SIG Windows therefore recognized the need for a tailored solution to ensure Windows nodes' operational readiness before their deployment into production environments. Thus, the idea to develop a Windows Operational Readiness Specification was born.

Can’t we just run the official Conformance tests?

The Kubernetes project contains a set of conformance tests, which are standardized tests designed to ensure that a Kubernetes cluster meets the required Kubernetes specifications.

However, these tests were originally defined at a time when Linux was the only operating system compatible with Kubernetes, and thus, they were not easily extendable for use with Windows. Given that Windows workloads, despite their importance, account for a smaller portion of the Kubernetes community, it was important to ensure that the primary conformance suite relied upon by many Kubernetes distributions to certify Linux conformance, didn't become encumbered with Windows specific features or enhancements such as GMSA or multi-operating system kube-proxy behavior.

Therefore, since there was a specialized need for Windows conformance testing, SIG Windows went down the path of offering Windows specific conformance tests through the Windows Operational Readiness Specification.

Can’t we just run the Kubernetes end-to-end test suite?

In the Linux world, tools such as Sonobuoy simplify execution of the conformance suite, relieving users from needing to be aware of Kubernetes' compilation paths or the semantics of Ginkgo tags.

Regarding needing to compile the Kubernetes tests, we realized that Windows users might similarly find the process of compiling and running the Kubernetes e2e suite from scratch similarly undesirable, hence, there was a clear need to provide a user-friendly, "push-button" solution that is ready to go. Moreover, regarding Ginkgo tags, applying conformance tests to Windows nodes through a set of Ginkgo tags would also be burdensome for any user, including Linux enthusiasts or experienced Windows system admins alike.

To bridge the gap and give users a straightforward way to confirm their clusters support a variety of features, the Kubernetes SIG for Windows found it necessary to therefore create the Windows Operational Readiness application. This application written in Go, simplifies the process to run the necessary Windows specific tests while delivering results in a clear, accessible format.

This initiative has been a collaborative effort, with contributions from different cloud providers and platforms, including Amazon, Microsoft, SUSE, and Broadcom.

A closer look at the Windows Operational Readiness Specification

The Windows Operational Readiness specification specifically targets and executes tests found within the Kubernetes repository in a more user-friendly way than simply targeting Ginkgo tags. It introduces a structured test suite that is split into sets of core and extended tests, with each set of tests containing categories directed at testing a specific area of testing, such as networking. Core tests target fundamental and critical functionalities that Windows nodes should support as defined by the Kubernetes specification. On the other hand, extended tests cover more complex features, more aligned with diving deeper into Windows-specific capabilities such as integrations with Active Directory. These goal of these tests is to be extensive, covering a wide array of Windows-specific capabilities to ensure compatibility with a diverse set of workloads and configurations, extending beyond basic requirements. Below is the current list of categories.

Category NameCategory Description
Core.NetworkTests minimal networking functionality (ability to access pod-by-pod IP.)
Core.StorageTests minimal storage functionality, (ability to mount a hostPath storage volume.)
Core.SchedulingTests minimal scheduling functionality, (ability to schedule a pod with CPU limits.)
Core.ConcurrentTests minimal concurrent functionality, (the ability of a node to handle traffic to multiple pods concurrently.)
Extend.HostProcessTests features related to Windows HostProcess pod functionality.
Extend.ActiveDirectoryTests features related to Active Directory functionality.
Extend.NetworkPolicyTests features related to Network Policy functionality.
Extend.NetworkTests advanced networking functionality, (ability to support IPv6)
Extend.WorkerTests features related to Windows worker node functionality, (ability for nodes to access TCP and UDP services in the same cluster)

How to conduct operational readiness tests for Windows nodes

To run the Windows Operational Readiness test suite, refer to the test suite's README, which explains how to set it up and run it. The test suite offers flexibility in how you can execute tests, either using a compiled binary or a Sonobuoy plugin. You also have the choice to run the tests against the entire test suite or by specifying a list of categories. Cloud providers have the choice of uploading their conformance results, enhancing transparency and reliability.

Once you have checked out that code, you can run a test. For example, this sample command runs the tests from the Core.Concurrent category:

./op-readiness --kubeconfig $KUBE_CONFIG --category Core.Concurrent

As a contributor to Kubernetes, if you want to test your changes against a specific pull request using the Windows Operational Readiness Specification, use the following bot command in the new pull request.

/test operational-tests-capz-windows-2019

Looking ahead

We’re looking to improve our curated list of Windows-specific tests by adding new tests to the Kubernetes repository and also identifying existing test cases that can be targetted. The long term goal for the specification is to continually enhance test coverage for Windows worker nodes and improve the robustness of Windows support, facilitating a seamless experience across diverse cloud environments. We also have plans to integrate the Windows Operational Readiness tests into the official Kubernetes conformance suite.

If you are interested in helping us out, please reach out to us! We welcome help in any form, from giving once-off feedback to making a code contribution, to having long-term owners to help us drive changes. The Windows Operational Readiness specification is owned by the SIG Windows team. You can reach out to the team on the Kubernetes Slack workspace #sig-windows channel. You can also explore the Windows Operational Readiness test suite and make contributions directly to the GitHub repository.

Special thanks to Kulwant Singh (AWS), Pramita Gautam Rana (VMWare), Xinqi Li (Google) and Marcio Morales (AWS) for their help in making notable contributions to the specification. Additionally, appreciation goes to James Sturtevant (Microsoft), Mark Rossetti (Microsoft), Claudiu Belu (Cloudbase Solutions) and Aravindh Puthiyaparambil (Softdrive Technologies Group Inc.) from the SIG Windows team for their guidance and support.