This page provides an overview of Kubernetes alpha features, and how to use them with Google Container Engine.
You can experiment with Kubernetes Alpha features on Google Container Engine by creating an Alpha Cluster. An Alpha Cluster is a short-lived cluster that is not covered by the Container Engine SLA and cannot be upgraded, but has all Kubernetes APIs and features enabled.
To learn how to create an Alpha Cluster, see Creating Container Clusters.
Alpha Clusters are the way to run stable Kubernetes releases with Alpha features that may be less stable. Alpha clusters cannot be upgraded, and are automatically deleted after 30 days. This allows users to test out Kubernetes features while they are still in development while still benefitting from the convenience of Google Container Engine.
New features in Kubernetes progress through multiple stages of maturity from early development, to Alpha, Beta, and Stable levels.
To ensure stability and production quality, Normal Google Container Engine clusters only enable Beta level or higher features. This is done partly because Alpha features are by definition still in development, and in particular because Alpha features are not not required to be upgradeable. Google Container Engine automatically upgrades the Kubernetes control plane, so allowing alpha features could jeopardize the reliability of the cluster if there are breaking changes in a new version. For those interested, detailed requirements for Alpha, Beta, and Stable as Kubernetes defines them are documented here.
When to use alpha clusters
Alpha Clusters are designed for expert users and early adopters to experiment with workloads that take advantage of new features before those features are finalized or production ready. If there's a Kubernetes feature you want to try on Google Container Engine that's still in alpha, you can create an Alpha Cluster and try it out.
How to use alpha clusters
Once your cluster is created, you can use it like any normal Container Engine cluster. Fetch credentials using
gcloud container clusters get-credentials CLUSTER
and you're ready to go. Need ideas? Try one of the stateful application examples in kubernetes/contrib.
By default, an Alpha Cluster lives for 30 days. Make sure any data is moved off of the cluster before the expiration date. You can see how many days the cluster has left by running
gcloud container clusters list
Latest Alpha Features
Each release of Kubernetes contains new Alpha features that you can try out in a Container Engine Alpha Cluster. Some of the major features are listed below. For a full list of Alpha features in the latest releases, see the Kubernetes changelog.
Features Available in Kubernetes 1.5
PetSet becomes StatefulSet - PetSet's name has changed to StatefulSet in version 1.5. StatefulSet is a beta feature available in regular Container Engine clusters, and PetSet is no longer available in Alpha Clusters.
Cascading Deletion for Federated resources - You can enable cascading deletion in a cluster federation, so that when you delete a resource from the federation control plane, that resource is deleted in the underlying clusters.
Features Available in Kubernetes 1.4
- Cron Jobs - time based Jobs, run once at a specified time or repeatedly at specified intervals. Cron Jobs was previously named Scheduled Jobs.