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Create a StatefulSet

Applies to: AKS on Windows Server

This article describes how to create, update, and delete StatefulSets, which are used to maintain the state of an application beyond a pod lifecycle in an AKS deployment in AKS on Windows Server.

Overview of StatefulSets

StatefulSets maintain the state of applications beyond an individual pod lifecycle. Like deployments, a StatefulSet creates and manages at least one identical pod with unique, persistent identities and stable host names. Replicas in a StatefulSet follow a sequential approach to deployment, scale, and upgrade.

A StatefulSet is useful for applications that require stable and unique identifiers, persistent storage, an ordered deployment, and scaling. Examples of these apps include MySQL, MongoDB, Kafka, and Cassandra. Stateless applications, such as Apache and Tomcat, aren't concerned with what network they're using and do not require persistent storage.

The main components of StatefulSets are the persistent volume provisioner and the headless service. For more information, see StatefulSets.

How to create a StatefulSet

You can create a StatefulSet using the kubectl create or the kubectl apply command. For example:

kubectl create –f statefulset.yaml

In the same manifest YAML file, you can also create the headless service that the StatefulSet uses.

To view the components you created for your StatefulSet, run the following command:

kubectl get statefulset

If you want to view persistent volumes, run kubectl get pv. To view a persistent volume claim, run kubectl get pvc.

Update StatefulSets

To update a StatefulSet, edit the manifest file, and run the same command used when creating the StatefulSet: kubectl apply –f statefulset.yaml.

You can use either an OnDelete update or a rolling update as the update strategy:

  • With an OnDelete update, pods are not replaced when you apply the manifest, but you must manually delete existing StatefulSet pods before the new version is created.
  • In a rolling update, StatefulSet pods are removed and then replaced in reverse ordinal order when you apply the manifest.

Delete a StatefulSet

Use the kubectl delete command to delete a StatefulSet and to delete the headless service separately. To delete the StatefulSet, run the following command:

kubectl delete statefulset <statefulset_NAME>

Then, to delete the headless service, run the following command:

kubectl delete service <svc_NAME>

To delete the persistent volume and the persistent volume claim, use the kubectl delete pv and kubectl delete pvc commands, respectively. To prevent data loss, the persistent volume and persistent volume claim aren't deleted when a StatefulSet is deleted.

Next steps