Kubernetes StatefulSet

External

• https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/ StatefulSets

Internal

• Kubernetes Higher Level Pod Controllers
• API Resources Concepts

Overview

Used for stateful application components, where the application component relies on access to "stable" file storage to maintain state between restarts. As such, local volumes that are directly attached to node hosts, can be used. A StatefulSet and the individual pods the StatefulSet manages are registered with the cluster's DNS service.

A stateful set makes sure pods are rescheduled in such a way that they retain their identity and state.

The StatefulSet creates PersistentVolumeClaims in a manner similar to the one in which it creates pods. More details in StatefulSet Storage below.

StatefulSet Manifest

StatefulSet Manifest

StatefulSet Storage

Persistent Volume Claim Template

Because persistent volume claims map to persistent volumes one-to-one, and each pod of a StatefulSet needs its dedicated, separate storage, each pod of a StatefulSet needs to reference a different persistent volume claim to have its own separate persistent volume. The StatefulSet achieves this behavior by creating persistent volume claims alongside pods, based on a persistent volume claim template.

Labels on a Persistent Volume Claim created from the Persistent Volume Claim Template

When the persistent volume claim associated with the pods are created, each persistent volume claim will automatically get all labels declared in the .spec.selector.matchLabels section of the StatefulSet manifes.

Persistent Volume Claim Template Manifest

StatefulSet Manifest

Operations

StatefulSet Operations