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Storage Object in Use Protection

Persistent volume claims (PVCs) that are in active use by a pod and persistent volumes (PVs) that are bound to PVCs can be protected from premature removal.

Before you begin
Storage Object in Use Protection feature used for PVC Protection
Storage Object in Use Protection feature used for PV Protection

Before you begin

The Storage Object in Use Protection feature is enabled in one of the below Kubernetes versions:

FEATURE STATE: Kubernetes v1.10 beta

This feature is currently in a beta state, meaning:

The version names contain beta (e.g. v2beta3).
Code is well tested. Enabling the feature is considered safe. Enabled by default.
Support for the overall feature will not be dropped, though details may change.
The schema and/or semantics of objects may change in incompatible ways in a subsequent beta or stable release. When this happens, we will provide instructions for migrating to the next version. This may require deleting, editing, and re-creating API objects. The editing process may require some thought. This may require downtime for applications that rely on the feature.
Recommended for only non-business-critical uses because of potential for incompatible changes in subsequent releases. If you have multiple clusters that can be upgraded independently, you may be able to relax this restriction.
Please do try our beta features and give feedback on them! After they exit beta, it may not be practical for us to make more changes.

FEATURE STATE: Kubernetes v1.11 stable

This feature is stable, meaning:

The version name is vX where X is an integer.
Stable versions of features will appear in released software for many subsequent versions.

Storage Object in Use Protection feature used for PVC Protection

The example below uses a GCE PD StorageClass, however, similar steps can be performed for any volume type.

Create a StorageClass for convenient storage provisioning:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: slow
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-standard

Verification scenarios follow below.

Scenario 1: The PVC is not in active use by a pod

Create a PVC:

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: slzc
spec:
accessModes:
- ReadWriteOnce
storageClassName: slow
resources:
requests:
  storage: 3.7Gi

Check that the PVC has the finalizer kubernetes.io/pvc-protection set:

kubectl describe pvc slzc
Name:          slzc
Namespace:     default
StorageClass:  slow
Status:        Bound
Volume:        pvc-bee8c30a-d6a3-11e7-9af0-42010a800002
Labels:        <none>
Annotations:   pv.kubernetes.io/bind-completed=yes
           pv.kubernetes.io/bound-by-controller=yes
           volume.beta.kubernetes.io/storage-provisioner=kubernetes.io/gce-pd
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      4Gi
Access Modes:  RWO
Events:
Type    Reason                 Age   From                         Message
----    ------                 ----  ----                         -------
Normal  ProvisioningSucceeded  2m    persistentvolume-controller  Successfully provisioned volume pvc-bee8c30a-d6a3-11e7-9af0-42010a800002 using kubernetes.io/gce-pd

Delete the PVC and check that the PVC (not in active use by a pod) was removed successfully.

Scenario 2: The PVC is in active use by a pod

Again, create the same PVC.

Create a pod that uses the PVC:

kind: Pod
apiVersion: v1
metadata:
name: app1
spec:
containers:
- name: test-pod
image: k8s.gcr.io/busybox:1.24
command:
  - "/bin/sh"
args:
  - "-c"
  - "date > /mnt/app1.txt; sleep 60 && exit 0 || exit 1"
volumeMounts:
  - name: path-pvc
    mountPath: "/mnt"
restartPolicy: "Never"
volumes:
- name: path-pvc
  persistentVolumeClaim:
    claimName: slzc

Wait until the pod status is Running, i.e. the PVC becomes in active use.

Delete the PVC that is now in active use by a pod and verify that the PVC is not removed but its status is Terminating:

Name:          slzc
Namespace:     default
StorageClass:  slow
Status:        Terminating (since Fri, 01 Dec 2017 14:47:55 +0000)
Volume:        pvc-803a1f4d-d6a6-11e7-9af0-42010a800002
Labels:        <none>
Annotations:   pv.kubernetes.io/bind-completed=yes
           pv.kubernetes.io/bound-by-controller=yes
           volume.beta.kubernetes.io/storage-provisioner=kubernetes.io/gce-pd
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      4Gi
Access Modes:  RWO
Events:
Type    Reason                 Age   From                         Message
----    ------                 ----  ----                         -------
Normal  ProvisioningSucceeded  52s   persistentvolume-controller  Successfully provisioned volume pvc-803a1f4d-d6a6-11e7-9af0-42010a800002 using kubernetes.io/gce-pd

Wait until the pod status is Terminated (either delete the pod or wait until it finishes). Afterwards, check that the PVC is removed.

Scenario 3: A pod starts using a PVC that is in Terminating state

Again, create the same PVC.

Create a first pod that uses the PVC:

kind: Pod
apiVersion: v1
metadata:
name: app1
spec:
containers:
- name: test-pod
image: k8s.gcr.io/busybox:1.24
command:
  - "/bin/sh"
args:
  - "-c"
  - "date > /mnt/app1.txt; sleep 600 && exit 0 || exit 1"
volumeMounts:
  - name: path-pvc
    mountPath: "/mnt"
restartPolicy: "Never"
volumes:
- name: path-pvc
  persistentVolumeClaim:
    claimName: slzc

Wait until the pod status is Running, i.e. the PVC becomes in active use.

Delete the PVC that is now in active use by a pod and verify that the PVC is not removed but its status is Terminating:

Name:          slzc
Namespace:     default
StorageClass:  slow
Status:        Terminating (since Fri, 01 Dec 2017 14:47:55 +0000)
Volume:        pvc-803a1f4d-d6a6-11e7-9af0-42010a800002
Labels:        <none>
Annotations:   pv.kubernetes.io/bind-completed=yes
           pv.kubernetes.io/bound-by-controller=yes
           volume.beta.kubernetes.io/storage-provisioner=kubernetes.io/gce-pd
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      4Gi
Access Modes:  RWO
Events:
Type    Reason                 Age   From                         Message
----    ------                 ----  ----                         -------
Normal  ProvisioningSucceeded  52s   persistentvolume-controller  Successfully provisioned volume pvc-803a1f4d-d6a6-11e7-9af0-42010a800002 using kubernetes.io/gce-pd

Create a second pod that uses the same PVC:

kind: Pod
apiVersion: v1
metadata:
name: app2
spec:
containers:
- name: test-pod
image: gcr.io/google_containers/busybox:1.24
command:
  - "/bin/sh"
args:
  - "-c"
  - "date > /mnt/app1.txt; sleep 600 && exit 0 || exit 1"
volumeMounts:
  - name: path-pvc
    mountPath: "/mnt"
restartPolicy: "Never"
volumes:
- name: path-pvc
  persistentVolumeClaim:
    claimName: slzc

Verify that the scheduling of the second pod fails with the below warning:

Warning  FailedScheduling  18s (x4 over 21s)  default-scheduler persistentvolumeclaim "slzc" is being deleted

Wait until the pod status of both pods is Terminated or Completed (either delete the pods or wait until they finish). Afterwards, check that the PVC is removed.

Storage Object in Use Protection feature used for PV Protection

The example below uses a HostPath PV.

Verification scenarios follow below.

Scenario 1: The PV is not bound to a PVC

Create a PV:

kind: PersistentVolume
apiVersion: v1
metadata:
name: task-pv-volume
labels:
type: local
spec:
capacity:
storage: 1Gi
accessModes:
- ReadWriteOnce
persistentVolumeReclaimPolicy: Delete
storageClassName: standard
hostPath:
path: "/tmp/data"

Check that the PV has the finalizer kubernetes.io/pv-protection set:

Name:            task-pv-volume
Labels:          type=local
Annotations:     pv.kubernetes.io/bound-by-controller=yes
Finalizers:      [kubernetes.io/pv-protection]
StorageClass:    standard
Status:          Terminating (lasts 1m)
Claim:           default/task-pv-claim
Reclaim Policy:  Delete
Access Modes:    RWO
Capacity:        1Gi
Message:         
Source:
Type:          HostPath (bare host directory volume)
Path:          /tmp/data
HostPathType:  
Events:            <none>

Delete the PV and check that the PV (not bound to a PVC) is removed successfully.

Scenario 2: The PV is bound to a PVC

Again, create the same PV.

Create a PVC

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: task-pv-claim
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
  storage: 1Gi

Wait until the PV and PVC are bound to each other.

Delete the PV and verify that the PV is not removed but its status is Terminating:

NAME             CAPACITY     ACCESS MODES   RECLAIM POLICY   STATUS        CLAIM                   STORAGECLASS   REASON    AGE
task-pv-volume   1Gi          RWO            Delete           Terminating   default/task-pv-claim   standard                 59s

Delete the PVC and verify that the PV is removed too.

kubectl delete pvc task-pv-claim
persistentvolumeclaim "task-pv-claim" deleted
$ kubectl get pvc
No resources found.
$ kubectl get pv
No resources found.

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