Expanding a StatefulSet controller volume

To increase the size of a volume for the StatefulSet controller without shutting down the service:

1. Create a StatefulSet controller.
2. Make changes to controller settings.

Before you start, install kubectl and configure it to work with the created Managed Service for Kubernetes cluster.

Create a StatefulSet controllerCreate a StatefulSet controller

1. Create a file named sts.yaml with a controller configuration:

   sts.yaml

   apiVersion: apps/v1
   kind: StatefulSet
   metadata:
     name: ubuntu-test
   spec:
     selector:
       matchLabels:
         app: ubuntu
     serviceName: "ubuntu"
     replicas: 3
     template:
       metadata:
         labels:
           app: ubuntu
       spec:
         terminationGracePeriodSeconds: 10
         containers:
         - name: ubuntu
           image: ubuntu
           command: ["/bin/sh"]
           args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
           volumeMounts:
           - mountPath: /data
             name: pvc-dynamic
     volumeClaimTemplates:
     - metadata:
         name: pvc-dynamic
       spec:
         accessModes: [ "ReadWriteOnce" ]
         storageClassName: "yc-network-hdd"
         resources:
           requests:
             storage: 1Gi
   

2. Create a controller:

   kubectl apply -f sts.yaml
   

   The command will create a StatefulSet controller named ubuntu-test comprising three pods. The size of PersistentVolumeClaim per pod is 1 GB.

3. Make sure the controller pod status changed to Running and PersistentVolumeClaim, to Bound:

   kubectl get pods,pvc
   

   Result:

   NAME               READY  STATUS   RESTARTS  AGE
   pod/ubuntu-test-0  1/1    Running  0         90s
   pod/ubuntu-test-1  1/1    Running  0         80s
   pod/ubuntu-test-2  1/1    Running  0         72s
   
   NAME                                             STATUS  VOLUME                                    CAPACITY  ACCESS MODES  STORAGECLASS    AGE
   persistentvolumeclaim/pvc-dynamic-ubuntu-test-0  Bound   pvc-603ac129-fe56-400a-8481-feaa********  1Gi       RWO           yc-network-hdd  91s
   persistentvolumeclaim/pvc-dynamic-ubuntu-test-1  Bound   pvc-a6fb0761-0771-483c-abfb-d4a8********  1Gi       RWO           yc-network-hdd  81s
   persistentvolumeclaim/pvc-dynamic-ubuntu-test-2  Bound   pvc-f479c8aa-426a-4e43-9749-5e0f********  1Gi       RWO           yc-network-hdd  73s
   

4. Make sure that, for objects with the k8s-csi prefix, the disk status changed to READY:

   yc compute disk list
   

   Result:

   +----------------------+--------------------------------------------------+------------+-------------------+--------+----------------------+-------------+
   |          ID          |                       NAME                       |    SIZE    |        ZONE       | STATUS |     INSTANCE IDS     | DESCRIPTION |
   +----------------------+--------------------------------------------------+------------+-------------------+--------+----------------------+-------------+
   | ef3b5ln111s3******** | k8s-csi-15319ac44278c2ff23f0df04ebdbe5a8******** | 1073741824 | ru-central1-a | READY  | ef3nrev9j72t******** |             |
   | ef3e617rmqri******** | k8s-csi-336f16a11f750525075d7c155ad26ae3******** | 1073741824 | ru-central1-a | READY  | ef3nrev9j72t******** |             |
   | ef3rfleqkit0******** | k8s-csi-ba784ddd49c7aabc63bcbfc45be3cc2e******** | 1073741824 | ru-central1-a | READY  | ef3nrev9j72t******** |             |
   +----------------------+--------------------------------------------------+------------+-------------------+--------+----------------------+-------------+
   

Make changes to controller settingsMake changes to controller settings

1. Save the current ubuntu-test controller configuration to a file named ubuntu-test-sts.yaml:

   kubectl get sts ubuntu-test --output yaml > ubuntu-test-sts.yaml
   

2. In ubuntu-test-sts.yaml, increase the value for the volumeClaimTemplates.spec.resources.requests.storage parameter from 1Gi to 2Gi:

   ...
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 2Gi
   

   Note

   There is no need to increase the corresponding value of 1Gi for the kubectl.kubernetes.io/last-applied-configuration parameter.

3. Delete the current ubuntu-test StatefulSet controller:

   kubectl delete statefulset ubuntu-test --cascade=orphan
   

4. Make sure the StatefulSet controller has been deleted:

   kubectl get sts
   

5. Delete the first pod, ubuntu-test-0:

   kubectl delete pod ubuntu-test-0
   

6. Make changes to the PersistentVolumeClaim of the deleted ubuntu-test-0 pod by increasing the storage size to 2 GB:

   kubectl patch pvc pvc-dynamic-ubuntu-test-0 --patch '{"spec": {"resources": {"requests": {"storage": "2Gi"}}}}'
   

7. Apply the changes to the ubuntu-test controller:

   kubectl apply -f ubuntu-test-sts.yaml
   

8. Reduce the number of the ubuntu-test controller pods to 1:

   kubectl scale statefulset ubuntu-test --replicas=1
   

9. Increase the storage size for the ubuntu-test-1 and ubuntu-test-2 pods to 2 GB:

   kubectl patch pvc pvc-dynamic-ubuntu-test-1 --patch '{"spec": {"resources": {"requests": {"storage": "2Gi"}}}}' && \
   kubectl patch pvc pvc-dynamic-ubuntu-test-2 --patch '{"spec": {"resources": {"requests": {"storage": "2Gi"}}}}'
   

10. Set the number of the ubuntu-test controller pods back to 3:

    kubectl scale statefulset ubuntu-test --replicas=3
    

11. Make sure PersistentVolume for the ubuntu-test controller has increased to 2 GB for each volume:

    kubectl get pv
    

    Result:

    NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                               STORAGECLASS     REASON   AGE
    pvc-603ac129-fe56-400a-8481-feaa********   2Gi        RWO            Delete           Bound    default/pvc-dynamic-ubuntu-test-0   yc-network-hdd            11m
    pvc-a6fb0761-0771-483c-abfb-d4a8********   2Gi        RWO            Delete           Bound    default/pvc-dynamic-ubuntu-test-1   yc-network-hdd            11m
    pvc-f479c8aa-426a-4e43-9749-5e0f********   2Gi        RWO            Delete           Bound    default/pvc-dynamic-ubuntu-test-2   yc-network-hdd            11m