跨多个 Pod 将持久卷安装为 ReadOnlyMany 时出现问题

Question

我在将 ReadOnlyMany 持久卷挂载到 GKE 上的多个 Pod 时遇到一些问题。目前，它仅安装在一个 Pod 上，无法安装在任何其他 Pod 上（由于第一个 Pod 正在使用该卷），导致部署仅限于一个 Pod。

我怀疑该问题与从卷快照填充的卷有关。

查看相关问题，我已经检查了spec.containers.volumeMounts.readOnly = true和spec.containers.volumes.persistentVolumeClaim.readOnly = true，这似乎是相关问题的最常见修复。

我在下面包含了相关的 yaml。任何帮助将不胜感激！

这是（大部分）部署规范：

spec:
  containers:
  - env:
    - name: GOOGLE_APPLICATION_CREDENTIALS
      value: /var/secrets/google/key.json
    image: eu.gcr.io/myimage
    imagePullPolicy: IfNotPresent
    name: monsoon-server-sha256-1
    resources:
      requests:
        cpu: 100m
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /mnt/sample-ssd
      name: sample-ssd
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  nodeName: gke-cluster-1-default-pool-3d6123cf-kcjo
  priority: 0
  restartPolicy: Always
  schedulerName: default-scheduler
  securityContext: {}
  serviceAccount: default
  serviceAccountName: default
  terminationGracePeriodSeconds: 29
  tolerations:
  - effect: NoExecute
    key: node.kubernetes.io/not-ready
    operator: Exists
    tolerationSeconds: 300
  - effect: NoExecute
    key: node.kubernetes.io/unreachable
    operator: Exists
    tolerationSeconds: 300
  volumes:
  - name: sample-ssd
    persistentVolumeClaim:
      claimName: sample-ssd-read-snapshot-pvc-snapshot-5
      readOnly: true

存储类别（也是该集群的默认存储类别）：

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: sample-ssd
provisioner: pd.csi.storage.gke.io
volumeBindingMode: Immediate
parameters:
    type: pd-ssd

聚氯乙烯：

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: sample-ssd-read-snapshot-pvc-snapshot-5
spec:
  storageClassName: sample-ssd
  dataSource:
    name: sample-snapshot-5
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
  accessModes:
    - ReadOnlyMany
  resources:
    requests:
      storage: 20Gi

Answer 1

Google Engineers are aware about this issue.

More details about this issue you can find in issue report and pull request on GitHub.

There's a temporary workaround if you're trying to provision a PD from a snapshot and make it ROX:

1. Provision a PVC with datasource as RWO;

It will create a new Compute Disk with the content of the source disk
2. Take the PV that was provisioned and copy it to a new PV that's ROX according to the docs

You can execute it with the following commands:

Step 1

Provision a PVC with datasource as RWO;

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: workaround-pvc
spec:
  storageClassName: ''
  dataSource:
    name: sample-ss
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi

You can check the disk name with command:

kubectl get pvc and check the VOLUME column. This is the disk_name

Step 2

Take the PV that was provisioned and copy it to a new PV that's ROX

As mentioned in the docs you need to create another disk using the previous disk (created in step 1) as source:

# Create a disk snapshot:
gcloud compute disks snapshot <disk_name>

# Create a new disk using snapshot as source
gcloud compute disks create pvc-rox --source-snapshot=<snapshot_name>

Create a new PV and PVC ReadOnlyMany

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-readonly-pv
spec:
  storageClassName: ''
  capacity:
    storage: 20Gi
  accessModes:
    - ReadOnlyMany
  claimRef:
    namespace: default
    name: my-readonly-pvc
  gcePersistentDisk:
    pdName: pvc-rox
    fsType: ext4
    readOnly: true
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-readonly-pvc
spec:
  storageClassName: ''
  accessModes:
    - ReadOnlyMany
  resources:
    requests:
      storage: 20Gi

如此处所述，添加readOnly: true您的volumes和volumeMounts

readOnly: true