Alpha clusters

This page provides an overview of how alpha clusters work in Google Kubernetes Engine (GKE). Access to alpha features and APIs works differently with alpha clusters than with other types of GKE clusters. You can create an alpha cluster or learn more about cluster configuration choices.

You can experiment with Kubernetes alpha features by creating an alpha cluster. Alpha clusters are short-lived clusters that run stable Kubernetes releases. All Kubernetes APIs, including alpha APIs, are enabled. By default, alpha clusters have all alpha feature gates enabled that are available with the Kubernetes version. Some beta feature gates are enabled, depending on the default for Kubernetes. You can also selectively enable or disable specific alpha or beta feature gates during cluster creation. Alpha clusters are designed for advanced users and early adopters to experiment with workloads that take advantage of new features before those features are production-ready.

Limitations

Alpha clusters have the following limitations:

Difference between alpha clusters and alpha GKE versions

Alpha clusters don't necessarily run "alpha" versions of GKE. The term alpha cluster means that alpha APIs are enabled regardless of the version of Kubernetes the cluster runs. Periodically, Google offers customers the ability to test and validate GKE versions that are not generally available. These early-access versions can be run as alpha clusters or as clusters without the Kubernetes alpha APIs enabled.

Feature gates and alpha clusters

Feature gates are a set of key-value pairs that toggle Kubernetes features. With alpha clusters, GKE enables the following:

  • Alpha feature gates: all feature gates at the alpha stages that are available with the Kubernetes version of your cluster
  • Beta feature gates: the feature gates at the beta stages that are available with the Kubernetes version of your cluster, and which are enabled by default by open source Kubernetes

For more information about which feature gates are available for a specific Kubernetes version, and which beta features are enabled by default (true), see Feature gates for Alpha or Beta features in the Kubernetes documentation. However, you can selectively enable or disable specific feature gates, modifying the default values set by GKE.

Feature gates are a distinct mechanism for feature enablement from Kubernetes APIs, and are managed differently by GKE clusters. With alpha clusters, all Kubernetes alpha APIs are enabled. If you enable or disable a feature gate for an alpha cluster, the enablement of Kubernetes APIs isn't affected. However, some Kubernetes APIs and Kubernetes feature gates work together, so disabling feature gates might cause issues with related APIs. Verify the connection between specific feature gates and APIs.

For more information about how GKE works with feature gates, see Feature gates.

To enable a cluster with a specific feature gate configuration, use the --alpha-cluster-feature-gates flag during cluster creation with the Google Cloud CLI. When you include this flag, you can modify which alpha and beta feature gates are enabled or disabled. For more information, see Create an alpha cluster.

Limitations for enabling feature gates with alpha clusters

When you enable feature gates with alpha clusters, understand the following additional limitations:

  • You can only create alpha clusters with specific feature gates by using the gcloud CLI. Cluster creation with the Google Cloud console or Terraform isn't supported.
  • Kubernetes alpha features that require additional configuration beyond enabling the feature gate aren't supported.
  • You can selectively enable or disable alpha or beta feature gates, but all Kubernetes alpha APIs are enabled.

Latest Kubernetes alpha features

Most Kubernetes releases contain new alpha features that you can test in alpha clusters. For a full list of Kubernetes releases and the features they include, see the Kubernetes changelog.

About feature stages

New Kubernetes features are introduced in four stages: early development, alpha, beta, and stable.

To provide stability and production quality, GKE clusters other than alpha clusters enable only features that are beta or higher. GKE doesn't enable alpha features on other types of GKE clusters because the features aren't production-ready or upgradeable.

Because GKE automatically upgrades the Kubernetes control plane and, by default, the worker nodes, enabling alpha features in production can jeopardize the reliability of the cluster if there are breaking changes in a new version.

To learn more about the stages of Kubernetes features, see Alpha, Beta, and Stable Versions in the Kubernetes documentation.

To learn more about determining which features are enabled for a given GKE control plane version, see Feature gates.

What's next