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Shoot Hibernation

Clusters are only needed 24 hours a day if they run productive workload. So whenever you do development in a cluster, or just use it for tests or demo purposes, you can save a lot of money if you scale-down your Kubernetes resources whenever you don’t need them. However, scaling them down manually can become time-consuming the more resources you have.

Gardener offers a clever way to automatically scale-down all resources to zero: cluster hibernation. You can either hibernate a cluster by pushing a button, or by defining a hibernation schedule.

To save costs, it’s recommended to define a hibernation schedule before the creation of a cluster. You can hibernate your cluster or wake up your cluster manually even if there’s a schedule for its hibernation.

What Is Hibernation?

When a cluster is hibernated, Gardener scales down the worker nodes and the cluster’s control plane to free resources at the IaaS provider. This affects:

  • Your workload, for example, pods, deployments, custom resources.
  • The virtual machines running your workload.
  • The resources of the control plane of your cluster.

What Isn’t Affected by the Hibernation?

To scale up everything where it was before hibernation, Gardener doesn’t delete state-related information, that is, information stored in persistent volumes. The cluster state as persistent in etcd is also preserved.

Hibernate Your Cluster Manually

The .spec.hibernation.enabled field specifies whether the cluster needs to be hibernated or not. If the field is set to true, the cluster’s desired state is to be hibernated. If it is set to false or not specified at all, the cluster’s desired state is to be awakened.

To hibernate your cluster, you can run the following kubectl command:

$ kubectl patch shoot -n $NAMESPACE $SHOOT_NAME -p '{"spec":{"hibernation":{"enabled": true}}}'

Wake Up Your Cluster Manually

To wake up your cluster, you can run the following kubectl command:

$ kubectl patch shoot -n $NAMESPACE $SHOOT_NAME -p '{"spec":{"hibernation":{"enabled": false}}}'

Create a Schedule to Hibernate Your Cluster

You can specify a hibernation schedule to automatically hibernate/wake up a cluster.

Let’s have a look into the following example:

  hibernation:
    enabled: false
    schedules:
    - start: "0 20 * * *" # Start hibernation every day at 8PM
      end: "0 6 * * *"    # Stop hibernation every day at 6AM
      location: "America/Los_Angeles" # Specify a location for the cron to run in

The above section configures a hibernation schedule that hibernates the cluster every day at 08:00 PM and wakes it up at 06:00 AM. The start or end fields can be omitted, though at least one of them has to be specified. Hence, it is possible to configure a hibernation schedule that only hibernates or wakes up a cluster. The location field is the time location used to evaluate the cron expressions.