CSI插件简介

CSI是Container Storage Interface的简称，为容器编排系统和存储系统之间建立一套标准的存储调用接口。

Kubernetes支持CSI接口标准，并在1.10版本进入beta阶段。K8S除了支持CSI方式提供存储接口外，还有In-Tree方式、Flexvolume方式提供的各种存储接口。

In-Tree方式是嵌入在K8S源码内部的存储挂载实现，存在以下问题：

存储插件需要一同随K8S发布。
存储插件的问题有可能会影响K8S部件正常运行。
存储插件享有K8S部件同等的特权存在安全隐患。
存储插件开发者必须遵循K8S社区的规则开发代码。

FlexVolume机制通过调用一个可执行文件方式去实现挂载，它能够做到让存储提供方进行独立开发维护。

部署可执行文件时，需要host的root权限，依然存在安全隐患。
存储插件在执行mount、attach操作时，往往需要到host去安装第三方工具或加载依赖库，这样会使部署变得复杂。

CSI标准的出现解决了上述问题，后续K8S与存储系统的集成标准将全面支持CSI。

阿里云存储支持CSI Plugin

目前阿里云CSI存储插件支持云盘、OSS、NAS等存储类型，并支持通过StorageClass创建动态存储卷；

开源地址：https://github.com/AliyunContainerService/csi-plugin

插件的部署拓扑如下：
csi-disk.png

使用演示

云盘CSI Plugin部署

环境准备

  1. 通过阿里云容器服务创建K8S集群（1.10版本及以上），或者自己通过阿里云ECS服务器搭建K8S集群。
  2. 配置Kubelet启动参数：--enable-controller-attach-detach=true；

部署 CSI Attacher

# kubectl create -f attacher.yaml

CSI attacher使用0.2.0版本，attacher.yaml内容如下：

# This YAML file contains RBAC API objects,
# which are necessary to run external csi attacher for cinder.

apiVersion: v1
kind: ServiceAccount
metadata:
  name: csi-attacher

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: external-attacher-runner
rules:
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get", "list", "watch"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["volumeattachments"]
    verbs: ["get", "list", "watch", "update"]

---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: csi-attacher-role
subjects:
  - kind: ServiceAccount
    name: csi-attacher
    namespace: default
roleRef:
  kind: ClusterRole
  name: external-attacher-runner
  apiGroup: rbac.authorization.k8s.io
---

kind: Service
apiVersion: v1
metadata:
  name: csi-attacher
  labels:
    app: csi-attacher
spec:
  selector:
    app: csi-attacher
  ports:
    - name: dummy
      port: 12345

---
kind: StatefulSet
apiVersion: apps/v1beta1
metadata:
  name: csi-attacher
spec:
  serviceName: "csi-attacher"
  replicas: 1
  template:
    metadata:
      labels:
        app: csi-attacher
    spec:
      tolerations:
      - effect: NoSchedule
        operator: Exists
        key: node-role.kubernetes.io/master
      - effect: NoSchedule
        operator: Exists
        key: node.cloudprovider.kubernetes.io/uninitialized
      nodeSelector:
         node-role.kubernetes.io/master: ""
      serviceAccount: csi-attacher
      containers:
        - name: csi-attacher
          image: registry.cn-hangzhou.aliyuncs.com/plugins/csi-attacher:v0.2.0
          args:
            - "--v=5"
            - "--csi-address=$(ADDRESS)"
          env:
            - name: ADDRESS
              value: /var/lib/kubelet/plugins/csi-diskplugin/csi.sock
          imagePullPolicy: "IfNotPresent"
          volumeMounts:
            - name: socket-dir
              mountPath: /var/lib/kubelet/plugins/csi-diskplugin
      volumes:
        - name: socket-dir
          hostPath:
            path: /var/lib/kubelet/plugins/csi-diskplugin
            type: DirectoryOrCreate

部署CSI Provsioner

# kubectl create -f provisioner.yaml

CSI provisioner使用0.2.0版本，内容如下：

apiVersion: v1
kind: ServiceAccount
metadata:
  name: csi-provisioner

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: external-provisioner-runner
rules:
  - apiGroups: [""]
    resources: ["secrets"]
    verbs: ["get", "list"]
  - 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: ["list", "watch", "create", "update", "patch"]

---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: csi-provisioner-role
subjects:
  - kind: ServiceAccount
    name: csi-provisioner
    namespace: default
roleRef:
  kind: ClusterRole
  name: external-provisioner-runner
  apiGroup: rbac.authorization.k8s.io

---
kind: Service
apiVersion: v1
metadata:
  name: csi-provisioner
  labels:
    app: csi-provisioner
spec:
  selector:
    app: csi-provisioner
  ports:
    - name: dummy
      port: 12345

---
kind: StatefulSet
apiVersion: apps/v1beta1
metadata:
  name: csi-provisioner
spec:
  serviceName: "csi-provisioner"
  replicas: 1
  template:
    metadata:
      labels:
        app: csi-provisioner
    spec:
      tolerations:
      - effect: NoSchedule
        operator: Exists
        key: node-role.kubernetes.io/master
      - effect: NoSchedule
        operator: Exists
        key: node.cloudprovider.kubernetes.io/uninitialized
      nodeSelector:
         node-role.kubernetes.io/master: ""
      serviceAccount: csi-provisioner
      containers:
        - name: csi-provisioner
          image: registry.cn-hangzhou.aliyuncs.com/plugins/csi-provisioner:v0.2.0
          args:
            - "--provisioner=csi-diskplugin"
            - "--csi-address=$(ADDRESS)"
            - "--v=5"
          env:
            - name: ADDRESS
              value: /var/lib/kubelet/plugins/csi-diskplugin/csi.sock
          imagePullPolicy: "IfNotPresent"
          volumeMounts:
            - name: socket-dir
              mountPath: /var/lib/kubelet/plugins/csi-diskplugin
      volumes:
        - name: socket-dir
          hostPath:
            path: /var/lib/kubelet/plugins/csi-diskplugin
            type: DirectoryOrCreate

部署Disk Plugin

Disk Plugin部署为DaemonSet应用，命令：

# kubectl create -f plugin.yaml

CSI driver-registrar使用0.2.0版本；

Socket地址设置为：/var/lib/kubelet/plugins/csi-diskplugin/csi.sock；

apiVersion: v1
kind: ServiceAccount
metadata:
  name: csi-diskplugin

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: csi-diskplugin
rules:
  - apiGroups: [""]
    resources: ["nodes"]
    verbs: ["get", "list", "update"]
  - apiGroups: [""]
    resources: ["namespaces"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["volumeattachments"]
    verbs: ["get", "list", "watch", "update"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: csi-diskplugin
subjects:
  - kind: ServiceAccount
    name: csi-diskplugin
    namespace: default
roleRef:
  kind: ClusterRole
  name: csi-diskplugin
  apiGroup: rbac.authorization.k8s.io

---
# This YAML file contains driver-registrar & csi driver nodeplugin API objects,
# which are necessary to run csi nodeplugin for disk.

kind: DaemonSet
apiVersion: apps/v1beta2
metadata:
  name: csi-diskplugin
spec:
  selector:
    matchLabels:
      app: csi-diskplugin
  template:
    metadata:
      labels:
        app: csi-diskplugin
    spec:
      tolerations:
        - key: node-role.kubernetes.io/master
          operator: Exists
          effect: NoSchedule
      serviceAccount: csi-diskplugin
      hostNetwork: true
      hostPID: true
      containers:
        - name: driver-registrar
          image: registry.cn-hangzhou.aliyuncs.com/plugins/driver-registrar:v0.2.0
          args:
            - "--v=5"
            - "--csi-address=$(ADDRESS)"
          env:
            - name: ADDRESS
              value: /var/lib/kubelet/plugins/csi-diskplugin/csi.sock
            - name: KUBE_NODE_NAME
              valueFrom:
                fieldRef:
                  fieldPath: spec.nodeName
          volumeMounts:
            - name: socket-dir
              mountPath: /var/lib/kubelet/plugins/csi-diskplugin
        - name: csi-diskplugin
          securityContext:
            privileged: true
            capabilities:
              add: ["SYS_ADMIN"]
            allowPrivilegeEscalation: true
          image: registry.cn-hangzhou.aliyuncs.com/plugins/csi-diskplugin:v1.10-7424d08
          args :
            - "--nodeid=$(NODE_ID)"
            - "--endpoint=$(CSI_ENDPOINT)"
            - "--v=5"
          env:
            - name: NODE_ID
              valueFrom:
                fieldRef:
                  fieldPath: spec.nodeName
            - name: CSI_ENDPOINT
              value: unix://var/lib/kubelet/plugins/csi-diskplugin/csi.sock
          imagePullPolicy: "IfNotPresent"
          volumeMounts:
            - name: plugin-dir
              mountPath: /var/lib/kubelet/plugins/csi-diskplugin
            - name: pods-mount-dir
              mountPath: /var/lib/kubelet/pods
              mountPropagation: "Bidirectional"
            - mountPath: /dev
              name: host-dev
            - mountPath: /sys
              name: host-sys
            - mountPath: /lib/modules
              name: lib-modules
              readOnly: true
            - mountPath: /run/dbus
              name: host-run
              readOnly: true
            - mountPath: /var/log/alicloud
              name: host-log
      volumes:
        - name: plugin-dir
          hostPath:
            path: /var/lib/kubelet/plugins/csi-diskplugin
            type: DirectoryOrCreate
        - name: pods-mount-dir
          hostPath:
            path: /var/lib/kubelet/pods
            type: Directory
        - name: socket-dir
          hostPath:
            path: /var/lib/kubelet/plugins/csi-diskplugin
            type: DirectoryOrCreate
        - name: host-dev
          hostPath:
            path: /dev
        - name: host-run
          hostPath:
            path: /run/dbus
        - name: host-sys
          hostPath:
            path: /sys
        - name: lib-modules
          hostPath:
            path: /lib/modules
        - name: host-log
          hostPath:
            path: /var/log/alicloud/

部署检查

# kubectl get pod

NAME                                 READY     STATUS    RESTARTS   AGE
csi-attacher-0                       1/1       Running   0          1d
csi-diskplugin-5w7wz                 2/2       Running   0          1d
csi-diskplugin-j99h9                 2/2       Running   0          1d
csi-diskplugin-ljg9s                 2/2       Running   0          1d
csi-diskplugin-nhbfp                 2/2       Running   0          1d
csi-provisioner-0                    1/1       Running   0          1d

使用CSI插件挂载云盘

下面以创建动态云盘数据卷为例，介绍如何使用CSI插件挂载；

创建云盘StorageClass

定义一个SSD、ReadWrite、北京B区的StorageClass；

# kubectl create -f storageclass.yaml

storageclass.yaml内容如下：

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
   name: csi-disk
provisioner: csi-diskplugin
parameters:
    zoneId: cn-beijing-b
    regionId: cn-beijing
    fsType: ext4
    type: cloud_ssd
    readOnly: "false"
reclaimPolicy: Delete

创建应用

创建Nginx服务并通过PVC挂载云盘，在PVC配置csi-disk storageClassName；

# kubectl create -f nginx.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: disk-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 25Gi
  storageClassName: csi-disk
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment1
  labels:
    app: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
        volumeMounts:
          - name: disk-pvc
            mountPath: "/data"
      volumes:
        - name: disk-pvc
          persistentVolumeClaim:
            claimName: disk-pvc

云盘挂载验证

查看nginx容器：

# kubectl get pod | grep nginx
# nginx-deployment1-5879d9db88-wr9j9   1/1       Running   0          1d

查看容器内挂载信息：

# kubectl exec -ti nginx-deployment1-5879d9db88-wr9j9 df | grep data
/dev/vdd        25671908   45084  24299720   1% /data
# kubectl exec -ti nginx-deployment1-5879d9db88-wr9j9 touch /data/aliyun
# kubectl exec -ti nginx-deployment1-5879d9db88-wr9j9 ls /data
aliyun    lost+found

删除容器，验证云盘高可用：

# kubectl delete pod nginx-deployment1-5879d9db88-wr9j9
# kubectl get pod
NAME                                 READY     STATUS    RESTARTS   AGE
nginx-deployment1-5879d9db88-mjb5p   1/1       Running   0          14s
# kubectl exec -ti nginx-deployment1-5879d9db88-mjb5p ls /data
aliyun    lost+found

上述操作通过CSI插件成功挂载阿里云云盘，并验证了应用数据的高可用性；

# 运维
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