问题描述

在使用**Kubernetes 1.20+**部署NFS Provisioner时，会发现在创建PersistentVolumeClaim 时状态始终为Pending，并抛出以下异常：

unexpected error getting claim reference: selfLink was empty, can't make reference

引起原因

SelfLink 字段存在于所有 Kubernetes 对象中，并包含表示给定对象的 URL。此字段不提供任何新信息，其创建和维护会影响性能。

最初在Kubernetes 1.16 中弃用，在1.20 版本中此功能现在默认禁用，最终将在后续版本中将此功能移除。更多关注# 1164

解决方案

方案1 、临时启用SelfLink

由于1.20版本该功能还未完成移除，可以在apiserver中selfLink功能临时启用，通过配置 apiserver 启动参数中的 --feature-gates 中的 RemoveSelfLink=false，可以重新启用该功能。

修改 /etc/kubernetes/manifests/kube-apiserver.yaml 文件，

在参数中新增加 - --feature-gates=RemoveSelfLink=false。

方案2、使用最新 provisioner镜像【推荐】

• helm 部署

$ helm repo add nfs-subdir-external-provisioner https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/
$ helm install nfs-subdir-external-provisioner nfs-subdir-external-provisioner/nfs-subdir-external-provisioner \
    --set nfs.server=x.x.x.x \
    --set nfs.path=/exported/path

• YAML部署

# 适用于1.20+版本
apiVersion: v1
kind: Namespace
metadata:
  name: nfs
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: nfs
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
rules:
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "create", "delete"]
  - apiGroups: [""]
    resources: ["persistentvolumeclaims"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["storageclasses"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "update", "patch"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: run-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: nfs
roleRef:
  kind: ClusterRole
  name: nfs-client-provisioner-runner
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: nfs
rules:
  - apiGroups: [""]
    resources: ["endpoints"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: nfs
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: nfs
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-nfs-storage
provisioner: k8s-sigs.io/nfs-subdir-external-provisioner # or choose another name, must match deployment's env PROVISIONER_NAME'
mountOptions:
  - vers=4.1
  - noresvport
  - noatime
parameters:
  mountOptions: "vers=4.1,noresvport,noatime"
  archiveOnDelete: "false" #archiveOnDelete定义为false时，删除NFS Server中对应的目录，为true则保留；

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nfs-client-provisioner
  labels:
    app: nfs-client-provisioner
  # replace with namespace where provisioner is deployed
  namespace: nfs
spec:
  replicas: 1
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nfs-client-provisioner
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner
      containers:
        - name: nfs-client-provisioner
          image: registry.cn-shenzhen.aliyuncs.com/shuhui/nfs-subdir-external-provisioner:v4.0.2
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: k8s-sigs.io/nfs-subdir-external-provisioner
            - name: NFS_SERVER
              value: 172.20.200.21
            - name: NFS_PATH
              value: /
      volumes:
        - name: nfs-client-root
          nfs:
            server: 172.20.200.21
            path: /

---

# Test PVC
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: test-claim
spec:
  storageClassName: managed-nfs-storage
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Mi
---
# Test Pod with PVC
kind: Pod
apiVersion: v1
metadata:
  name: test-pod
spec:
  containers:
  - name: test-pod
    image: busybox:stable
    command:
      - "/bin/sh"
    args:
      - "-c"
      - "touch /mnt/SUCCESS && exit 0 || exit 1"
    volumeMounts:
      - name: nfs-pvc
        mountPath: "/mnt"
  restartPolicy: "Never"
  volumes:
    - name: nfs-pvc
      persistentVolumeClaim:
        claimName: test-claim

• 设置为默认StorageClass【可选】

# kubectl patch storageclass managed-nfs-storage -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

参考引用

• [1] https://github.com/kubernetes-sigs/nfs-subdir-external-provisioner
• [2] https://github.com/kubernetes/enhancements/issues/1164