PVC Expansion Through StatefulSet Modification ​

Feature Introduction ​

When the product management scale expands, it is necessary to adjust business instances, resource quotas, and storage resources. However, the PVC template size of a StatefulSet does not support modification, requiring manual PVC size adjustments during expansion, which is time-consuming. This feature aims to support automatic PVC expansion by modifying the PVC template size of a StatefulSet.

Use Cases ​

When the product management scale expands and business instances, resource quotas, and storage resources need to be adjusted, expansion is achieved by modifying the StatefulSet template.

Supported Scope ​

StatefulSet resources with PVC configured already exist in the cluster, and the SC feature switch is enabled.

Highlights ​

Enables automatic PVC expansion by modifying the PVC template size of a StatefulSet.

Implementation Principle ​

• Add FeatureGate: HWStatefulSetVolumeExpansion, applying to kube-apiserver and kube-controller-manager, used to enable the capability to expand PVCs by modifying StatefulSets.

• Existing features already support expanding storage resources by modifying PVCs. Currently, we only need to monitor PVC size changes declared in the StatefulSet controller and dynamically patch the PVC's storage size to achieve dynamic storage expansion.

• The StatefulSet controller adds a listener for PVC update events to update the StatefulSet status.

• Add an extended field to StatefulSet to represent the status of volumeClaimTemplates modifications.

  yaml

    status: 
      availableReplicas: 3 
      currentReplicas: 3 
      currentRevision: ex1-54c5bd476c 
      readyReplicas: 3 
      replicas: 3 
      updatedReplicas: 3 
      volumeClaimTemplates: 
      - finishedReconciliationGeneration: 2 
        readyReplicas: 1 
        templateName: vol1

Relationship with Related Features ​

None.

Installation ​

No installation required.

Using PVC Expansion ​

Prerequisites ​

None.

Background Information ​

None.

Usage Restrictions ​

None.

Procedure ​

Using this feature requires enabling the Local CSI allowVolumeExpansion functionality, and automatic expansion is achieved by modifying the PVC definition.

1. Check whether the feature is enabled:

   shell

   kubectl get sc -A

   1.1 Check whether the allowVolumeExpansion value of Local CSI is true (enabled).

   1.2 If allowVolumeExpansion is false, run the following command to enable it:

   shell

   kubectl edit sc <sc_name>

2. Query all StatefulSets:

   shell

   kubectl get sts -A

3. Modify the target StatefulSet to change the PVC size configuration:

   shell

   kubectl edit sts -n <namespace> <sts_name>

Find the PVC definition section and modify the storage size. The corresponding section format is as follows:

  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      # ...
    spec:
      # ...
      resource:
        requests:
          storage: 30Gi  # Modify this value
      # ...
    # ...