k8s 学习笔记之 statefulset 应用为何总是pending 状态

k8s pv 和 PVC 为何绑定不上

使用statefuset 部署有状态应用，应用总是处于pending 状态,在开始之前先介绍什么是statefuset, 在 k8s 中一般用 deployment 管理无状态应用，statefuset 用来管理有状态应用，如 redis 、mysql 、zookper 等分布式应用，这些应用的启动停止都会有严格的顺序

一、statefulset

headless (无头服务),没有cluserIP, 资源标识符，用于生成可解析的dns 记录
StatefulSet 用于pod 资源的管理
volumeClaimTemplates 提供存储

二、statefulset 部署

使用nfs 做网络存储
搭建nfs
配置共享存储目录
创建pv
编排 yaml

搭建nfs

yum install nfs-utils -y

mkdir -p /usr/local/k8s/redis/pv{7..12} # 创建挂载目录

 cat /etc/exports
 
 /usr/local/k8s/redis/pv7 172.16.0.0/16(rw,sync,no_root_squash)
 /usr/local/k8s/redis/pv8 172.16.0.0/16(rw,sync,no_root_squash)
 /usr/local/k8s/redis/pv9 172.16.0.0/16(rw,sync,no_root_squash)
 /usr/local/k8s/redis/pv10 172.16.0.0/16(rw,sync,no_root_squash)
 /usr/local/k8s/redis/pv11 172.16.0.0/16(rw,sync,no_root_squash

  exportfs -avr

创建pv

cat nfs_pv2.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv7
spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: slow
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv7"
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv8

spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  storageClassName: slow
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv8"
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv9

spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  storageClassName: slow
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv9"
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv10

spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  storageClassName: slow
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv10"
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv11

spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  storageClassName: slow
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv11"
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv12

spec:
  capacity:
    storage: 500M
  accessModes:
    - ReadWriteMany
  storageClassName: slow
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 172.16.0.59
    path: "/usr/local/k8s/redis/pv12"

kubectl apply -f nfs_pv2.yaml

查看 # 创建成功

编写yaml 编排应用

apiVersion: v1
kind: Service
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: myapp-pod
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: myapp
spec:
  serviceName: myapp
  replicas: 3
  selector:
    matchLabels:
      app: myapp-pod
  template:
    metadata:
      labels:
        app: myapp-pod
    spec:
      containers:
      - name: myapp
        image: ikubernetes/myapp:v1
        resources:
          requests:
            cpu: "500m"
            memory: "500Mi"
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: myappdata
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: myappdata
    spec:
      accessModes: ["ReadWriteOnce"]
      storageClassName: "slow"
      resources:
        requests:
          storage: 400Mi

kubectl create -f new-stateful.yaml

查看headless 创建成功

查看pod 是否创建成功

查看pvc 是否创建成功

pod 启动没有成功，依赖于pvc ，查看pvc 的日志,没有找到对应的pvc,明明写了啊

查看关联信息，有下面这个属性

storageClassName: "slow"

三、statefulset 排障

pvc 无法创建，导致pod 无法正常启动，yaml 文件重新检查了几遍，

思考的方向：pvc 如何绑定pv ，通过storageClassName 去关联，pv 也创建成功了，也存在storageClassName: slow 这个属性，结果愣是找不到

。。。。

后面检查pv 和pvc 的权限是否一直

发现pv 设置的权限

volumeClaimTemplates: 声明的pvc 权限

两边的权限不一致，

操作

删除 pvc kubectl delete pvc myappdata-myapp-0 -n daemon

删除 yaml 文件， kubectl delete -f new-stateful.yaml -n daemon

尝试修改 accessModes: ["ReadWriteMany"]

再次查看

提示：pv 和PVC 设定权限注

四、statefulset 测试，域名解析

kubectl exec -it myapp-0 sh -n daemon

nslookup myapp-0.myapp.daemon.svc.cluster.local

解析的规则如下

myapp-0 myapp daemon

FQDN： $(podname).(headless server name).namespace.svc.cluster.local

容器里面如没有nsllokup ,需要安装对应的包，busybox 可以提供类似的功能

提供yaml 文件

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: daemon
spec:
  containers:
  - name: busybox
    image: busybox:1.28.4
    command:
      - sleep
      - "7600"
    resources:
      requests:
        memory: "200Mi"
        cpu: "250m"
    imagePullPolicy: IfNotPresent
  restartPolicy: Never