Kubernetes系列之基於NFS的PV動態供給(StorageClass)

一、簡介

PersistentVolume（PV）是指由集羣管理員配置提供的某存儲系統上的段存儲空間，它是對底層共享存儲的抽象，將共享存儲作爲種可由用戶申請使的資源，實現了“存儲消費”機制。通過存儲插件機制，PV支持使用多種網絡存儲系統或雲端存儲等多種後端存儲系統，例如，NFS、RBD和Cinder等。PV是集羣級別的資源，不屬於任何名稱空間，用戶對PV資源的使需要通過PersistentVolumeClaim（PVC）提出的使申請（或稱爲聲明）來完成綁定，是PV資源的消費者，它向PV申請特定大小的空間及訪問模式（如rw或ro），從創建出PVC存儲卷，後再由Pod資源通過PersistentVolumeClaim存儲卷關聯使，如下圖：

儘管PVC使得用戶可以以抽象的方式訪問存儲資源，但很多時候還是會涉及PV的不少屬性，例如，由於不同場景時設置的性能參數等。爲此，集羣管理員不得不通過多種方式提供多種不同的PV以滿不同用戶不同的使用需求，兩者銜接上的偏差必然會導致用戶的需求無法全部及時有效地得到滿足。Kubernetes從1.4版起引入了一個新的資源對象StorageClass，可用於將存儲資源定義爲具有顯著特性的類（Class）而不是具體的PV，例如“fast”“slow”或“glod”“silver”“bronze”等。用戶通過PVC直接向意向的類別發出申請，匹配由管理員事先創建的PV，或者由其按需爲用戶動態創建PV，這樣做甚至免去了需要先創建PV的過程。
PV對存儲系統的支持可通過其插件來實現，目前，Kubernetes支持如下類型的插件。
官方地址：https://kubernetes.io/docs/concepts/storage/storage-classes/

由上圖我們可以看到官方插件是不支持NFS動態供給的，但是我們可以用第三方的插件來實現，下面就是本文要講的。

二、安裝NFS插件

GitHub地址：https://github.com/kubernetes-incubator/external-storage/tree/master/nfs-client/deploy

1、下載所需文件

for file in class.yaml deployment.yaml rbac.yaml  ; do wget https://raw.githubusercontent.com/kubernetes-incubator/external-storage/master/nfs-client/deploy/$file ; done

2、創建RBAC授權

# cat rbac.yaml
kind: ServiceAccount
apiVersion: v1
metadata:
  name: nfs-client-provisioner
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
rules:
  - 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
    namespace: default
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
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
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

3、創建Storageclass類

# cat class.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-nfs-storage
provisioner: fuseim.pri/ifs # or choose another name, must match deployment's env PROVISIONER_NAME'
parameters:
  archiveOnDelete: "false"

4、創建NFS的deployment，修改相應的NFS服務器IP及掛載路徑

# cat deployment.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner
---
kind: Deployment
apiVersion: apps/v1
metadata:
  name: nfs-client-provisioner
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nfs-client-provisioner
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner
      containers:
        - name: nfs-client-provisioner
          image: quay.io/external_storage/nfs-client-provisioner:v2.0.0
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: fuseim.pri/ifs
            - name: NFS_SERVER
              value: 192.168.1.100
            - name: NFS_PATH
              value: /huoban/k8s
      volumes:
        - name: nfs-client-root
          nfs:
            server: 192.168.1.100
            path: /huoban/k8s

三、創建一個PV動態供給應用實例

下面是一個StatefulSet應用動態申請PV的示意圖：

例如：創建一個nginx動態獲取PV

# cat nginx.yaml
---
apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx
  serviceName: "nginx"
  replicas: 3
  template:
    metadata:
      labels:
        app: nginx
    spec:
      imagePullSecrets:
      - name: huoban-harbor
      terminationGracePeriodSeconds: 10
      containers:
      - name: nginx
        image: harbor.huoban.com/open/huoban-nginx:v1.1
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: "managed-nfs-storage"
      resources:
        requests:
          storage: 1Gi

啓動之後我們可以看到一下信息

# kubectl get pod,pv,pvc
NAME                                         READY   STATUS    RESTARTS   AGE
pod/nfs-client-provisioner-fcb58977d-l5cs4   1/1     Running   0          20h
pod/web-0                                    1/1     Running   0          175m
pod/web-1                                    1/1     Running   0          175m
pod/web-2                                    1/1     Running   0          175m

NAME                                                                           CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                STORAGECLASS          REASON   AGE
persistentvolume/default-test-claim-pvc-e5a66781-b46e-4191-8f51-5d1a571ca530   1Mi        RWX            Delete           Bound    default/test-claim   managed-nfs-storage            20h
persistentvolume/default-www-web-0-pvc-0a578ef2-63e3-49bb-87c0-88166d3e0e65    1Gi        RWO            Delete           Bound    default/www-web-0    managed-nfs-storage            20h
persistentvolume/default-www-web-1-pvc-78061eb6-c36b-44db-9472-f2684f85a4b9    1Gi        RWO            Delete           Bound    default/www-web-1    managed-nfs-storage            20h
persistentvolume/default-www-web-2-pvc-ec760344-a35a-4048-b8aa-6452d6a62337    1Gi        RWO            Delete           Bound    default/www-web-2    managed-nfs-storage            20h

NAME                               STATUS   VOLUME                                                        CAPACITY   ACCESS MODES   STORAGECLASS          AGE
persistentvolumeclaim/test-claim   Bound    default-test-claim-pvc-e5a66781-b46e-4191-8f51-5d1a571ca530   1Mi        RWX            managed-nfs-storage   20h
persistentvolumeclaim/www-web-0    Bound    default-www-web-0-pvc-0a578ef2-63e3-49bb-87c0-88166d3e0e65    1Gi        RWO            managed-nfs-storage   20h
persistentvolumeclaim/www-web-1    Bound    default-www-web-1-pvc-78061eb6-c36b-44db-9472-f2684f85a4b9    1Gi        RWO            managed-nfs-storage   20h
persistentvolumeclaim/www-web-2    Bound    default-www-web-2-pvc-ec760344-a35a-4048-b8aa-6452d6a62337    1Gi        RWO            managed-nfs-storage   20h

現在，我們在NFS服務器上也可以看到自動生成了3個掛載目錄，單pod刪除之後數據還會存在

# ll
drwxrwxrwx 2 root root 4096 Oct 23 17:31 default-www-web-0-pvc-0a578ef2-63e3-49bb-87c0-88166d3e0e65
drwxrwxrwx 2 root root 4096 Oct 23 17:31 default-www-web-1-pvc-78061eb6-c36b-44db-9472-f2684f85a4b9
drwxrwxrwx 2 root root 4096 Oct 23 17:40 default-www-web-2-pvc-ec760344-a35a-4048-b8aa-6452d6a62337

StatefulSet應用有以下特點：

1.唯一的網絡標識

2.域名訪問(<statefulsetName-index>.<service-name>.svc.cluster.local) 如：web-0.nginx.default.svc.cluster.local

3.獨立的持久存儲

4.有序的部署和刪除

Kubernetes系列之基於NFS的PV動態供給(StorageClass)

一、簡介

二、安裝NFS插件

三、創建一個PV動態供給應用實例

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