statefulset为通用的有状态应用控制器。

每个pod都有自己的唯一标识，故障时，它只能被拥有同一个标识的新实例所取代。

如果有必要，可以为每个pod配置专用的存储卷，且只能是PVC格式。通过pvc模板来为每个pod创建专用PV

statefulset配置规范

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apiVersion: apps/v1  # API群组及版本；
kind: StatefulSet  # 资源类型的特有标识
metadata:
  name <string>  # 资源名称，在作用域中要唯一
  namespace <string>  # 名称空间；StatefulSet隶属名称空间级别
spec:
  replicas <integer> # 期望的Pod副本数，默认为1
  selector <object> # 标签选择器，须匹配Pod模板中的标签，必选字段
  template <object>  # Pod模板对象，必选字段
  revisionHistoryLimit <integer> # 滚动更新历史记录数量，默认为10
  updateStrategy <Object> # 滚动更新策略
    type <string>  # 滚动更新类型，可用值有OnDelete和Rollingupdate
    rollingUpdate <Object>  # 滚动更新参数，专用于RollingUpdate类型
      partition <integer>  # 分区指示索引值，默认为0
  serviceName  <string>  # 相关的Headless Service的名称，必选字段
  volumeClaimTemplates <[]Object>  # 存储卷申请模板
    apiVersion <string>  # PVC资源所属的API群组及版本，可省略
    kind <string>  # PVC资源类型标识，可省略
    metadata <Object>  # 卷申请模板元数据
    spec <Object>  # 期望的状态，可用字段同PVC
  podManagementPolicy  <string> # Pod管理策略，默认的“OrderedReady”表示顺序创
                                     #建并逆序删除，另一可用值“Parallel”表示并行模式

statefulset资源清单示例

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apiVersion: v1
kind: Service
metadata:
  name: demoapp-sts
  namespace: default
spec:
  clusterIP: None
  ports:
  - port: 80
    name: http
  selector:
    app: demoapp
    controller: sts-demo
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: sts-demo
spec:
  serviceName: demoapp-sts
  replicas: 2
  selector:
    matchLabels:
      app: demoapp
      controller: sts-demo
  template:
    metadata:
      labels:
        app: demoapp
        controller: sts-demo
    spec:
      containers:
      - name: demoapp
        images: ikubernetes/demoapp:v1.0
        ports:
        - name: web
          containerPort: 80
        volumeMounts:
        - name: appdata
          mountPath: /app/data
  volumeClaimTemplates:
  - metadata:
      name: appdata
    spec:
      accessModes: ["ReadWriteOnce"]
      storageClassName: longhorn
      resources:
        requests:
          storage: 2Gi
        limits:
          storage: 5Gi

StatefulSet示例

1.编写资源清单

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root@k8s-master01:~/yaml/chapter08# vim demodb.yaml
apiVersion: v1
kind: Service
metadata:
  name: demodb
  namespace: default
  labels:
    app: demodb
spec:
  clusterIP: None
  ports:
  - port: 9907
  selector:
    app: demodb
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: demodb
  namespace: default
spec:
  serviceName: demodb
  selector:
    matchLabels:
      app: demodb
  replicas: 2
  template:
    metadata:
      labels:
        app: demodb
    spec:
      containers:
      - name: demodb-shard
        image: ikubernetes/demodb:v0.1
        ports:
        - containerPort: 9907
          name: db
        env:
        - name: DEMODB_DATADIR
          value: "/demodb/data"
        livenessProbe:
          initialDelaySeconds: 2
          periodSeconds: 10
          httpGet:
            path: /status
            port: db
        readinessProbe:
          initialDelaySeconds: 15
          periodSeconds: 30
          httpGet:
            path: /status?level=full
            port: db
        volumeMounts:
        - name: data
          mountPath: /demodb/data
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: ["ReadWriteOnce"]
      storageClassName: longhorn
      resources:
        requests:
          storage: 2Gi
        limits:
          storage: 5Gi

2.应用配置清单

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root@k8s-master01:~/yaml/chapter08# kubectl apply -f demodb.yaml
service/demodb created
statefulset.apps/demodb created

3.查看pod信息

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root@k8s-master01:~/yaml/chapter08# kubectl get pods
NAME                                             READY   STATUS              RESTARTS   AGE
demodb-0                                         1/1     Running             0          3m
demodb-1                                         1/1     Running             0          2m
demodb-2                                         1/1     Running             0          1m

root@k8s-master01:~/yaml/chapter08# kubectl get sts
NAME     READY   AGE
demodb   3/3     4m

StatefulSet扩容

对镜像更新有3种方法：

  1. 修改资源配置清单后apply
  2. 使用kubectl set 命令
  3. 使用kubectl patch命令打补丁

此处示范打补丁

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# 对sts扩容
root@k8s-master01:~# kubectl patch statefulsets.apps demodb -p '{"spec":{"replicas":5}}'
statefulset.apps/demodb patched

# 查看扩容后的pod
root@k8s-master01:~# kubectl get pods -l 'app=demodb'
NAME       READY   STATUS    RESTARTS   AGE
demodb-0   1/1     Running   0          118m
demodb-1   1/1     Running   0          117m
demodb-2   1/1     Running   0          116m
demodb-3   1/1     Running   0          106s
demodb-4   0/1     Running   0          43s

StatefulSet缩容

1.使用patch进行缩容

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root@k8s-master01:~# kubectl patch statefulsets.apps demodb -p '{"spec":{"replicas":2}}'
statefulset.apps/demodb patched
# 此时多余的pod已经被删减

2.查看其所关联的pvc

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root@k8s-master01:~# kubectl get pvc
NAME                    STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
data-demodb-0           Bound    pvc-04997889-b711-4168-bb4c-54189c8f481f   2Gi        RWO            longhorn       3h30m
data-demodb-1           Bound    pvc-2d3e2083-659f-42ae-a289-99b2aa4199ea   2Gi        RWO            longhorn       3h29m
data-demodb-2           Bound    pvc-7017741e-4eef-42a2-8aba-409e6c680c3f   2Gi        RWO            longhorn       3h28m
data-demodb-3           Bound    pvc-2c82047a-8959-4f79-9cca-bcc0517d77da   2Gi        RWO            longhorn       93m
data-demodb-4           Bound    pvc-f5dc549c-1198-43aa-a39e-7dd36edea642   2Gi        RWO            longhorn       92m

# PVC依旧存在