(十一)Kubernetes StatefulSet控制器

StatefulSet介绍

前面使用Deployment创建的Pod是无状态的，当挂载了volume之后，如果该Pod挂了，Replication Controller会再启动一个Pod来保证可用性，但是由于Pod是无状态的，pod挂了就会和之前的Volume的关系断开，新创建的Pod无法找到之前的Pod。但是对于用户来说，他们对底层的Pod挂了是没有感知的，但是当Pod挂了之后就无法再使用之前挂载的存储卷。为了解决这一问题，就引入了StatefulSet用于保留Pod的状态信息。

StatefulSet是Pod资源控制器的一种实现，用于部署和扩展有状态应用的Pod资源，确保它们的运行顺序及每个Pod资源的唯一性。其应用场景包括：

• 稳定的持久化存储，即Pod重新调度后还是能访问到相同的持久化数据，基于PVC来实现。

• 稳定的网络标识，即Pod重新调度后其PodName和HostName不变，基于Headless Service（即没有Cluster IP的Service）来实现

• 有序部署，有序扩展，即Pod是有顺序的，在部署或者扩展的时候要依据定义的顺序依次进行（即从0到N-1，在下一个Pod运行之前的所有之前的Pod必须都是Running和Ready状态），基于init Containers来实现

• 有序收缩，有序删除（即从N-1到0）

StatefulSet由以下几个部分组成：

• 用于定义网络标志（DNS domain）和Headless Service

• 用于创建PersistentVolumes和VolumeClaimTemplates

• 定义具体应用的StatefulSet

StatefulSet中的每个Pod的DNS格式为statefulSetName-{0..N-1}.serviceName.namespace.svc.cluster.local，其中

• serviceName：为Headless Service的名字

• 0..N-1：为Pod所在的序号，从0开始到N-1

• statefulSetName：为StatefulSet的名字

• namespace：为服务所在的namaspace，Headless Service和StatefulSet必须在相同的namespace

• .cluster.local：为Cluster Domain

为什么要有headless？

在Deployment中，每一个pod是没有名称，是随机字符串，是无序的。而statefulSet中是要求有序的，每一个Pod的名称必须是固定的。当节点挂了，重建之后的标识符是不变的，每一个节点的节点名称是不会改变的。Pod名称是作为Pod识别的唯一标识符，必须保证其标识符的稳定并且唯一。

为了实现标识符的稳定，这时候就需要一个headless service解析直达到Pod，还需要给Pod配置一个唯一的名称。

为什么要有volumeClainTemplate？

大部分有状态副本集都会用到持久存储，比如分布式系统来说，由于数据是不一样的，每个节点都需要自己专用的存储节点。而在Deployment中Pod模板中创建的存储卷是一个共享的存储卷，多个Pod使用同一个存储卷，而statefulSet定义中的每一个Pod都不能使用同一个存储卷，由此基于Pod模板创建Pod是不适应的，这就需要引入volumeClainTemplate，当在使用StatefulSet创建Pod时，会自动生成一个PVC，从而请求绑定一个PV，从而有自己专用的存储卷。

Pod名称、PVC和PV的关系图如下：

StatefulSet定义

在创建StatefulSet之前需要准备的东西，创建顺序非常关键，如下

1、Volume

2、Persistent Volume

3、Persistent Volume Clain

4、Service

5、StatefulSet

Volume可以有很多中类型，比如nfs、gluster等，下面使用nfs

statefulSet字段说明：

[root@k8s-master ~]# kubectl explain statefulset
KIND:     StatefulSet
VERSION:  apps/v1

DESCRIPTION:
     StatefulSet represents a set of pods with consistent identities. Identities
     are defined as: - Network: A single stable DNS and hostname. - Storage: As
     many VolumeClaims as requested. The StatefulSet guarantees that a given
     network identity will always map to the same storage identity.
FIELDS:
   apiVersion    <string>
   kind    <string>
   metadata    <Object>
   spec    <Object>
   status    <Object>

[root@k8s-master ~]# kubectl explain statefulset.spec
podManagementPolicy    <string>    #Pod管理策略
replicas    <integer>    #Pod副本数量
revisionHistoryLimit    <integer>    #历史版本限制
selector    <Object> -required-    #标签选择器，根据标签选择管理的Pod资源；必选字段
serviceName    <string> -required-    #服务名称，必选字段
template    <Object> -required-    #模板，定义pod资源，必选字段
updateStrategy    <Object>    #更新策略
volumeClaimTemplates    <[]Object>    #存储卷申请模板，列表对象形式

示例，清单定义StatefulSet

通过上面的描述，下面示例定义StatefulSet资源，在定义之前首先得准备PV资源对象。这里同样使用NFS作为后端存储。

1）准备NFS（安装软件省略，参考）

(1)创建存储卷对应的目录
[root@storage ~]# mkdir /data/volumes/v{1..5} -p

(2)修改nfs的配置文件
[root@storage ~]# vim /etc/exports
/data/volumes/v1  192.168.1.0/24(rw,no_root_squash)
/data/volumes/v2  192.168.1.0/24(rw,no_root_squash)
/data/volumes/v3  192.168.1.0/24(rw,no_root_squash)
/data/volumes/v4  192.168.1.0/24(rw,no_root_squash)
/data/volumes/v5  192.168.1.0/24(rw,no_root_squash)

(3)查看nfs的配置
[root@storage ~]# exportfs -arv
exporting 192.168.1.0/24:/data/volumes/v5
exporting 192.168.1.0/24:/data/volumes/v4
exporting 192.168.1.0/24:/data/volumes/v3
exporting 192.168.1.0/24:/data/volumes/v2
exporting 192.168.1.0/24:/data/volumes/v1

(4)使配置生效
[root@storage ~]# showmount -e
Export list for storage:
/data/volumes/v5 192.168.1.0/24
/data/volumes/v4 192.168.1.0/24
/data/volumes/v3 192.168.1.0/24
/data/volumes/v2 192.168.1.0/24
/data/volumes/v1 192.168.1.0/24

2）创建PV；这里创建5个PV，存储大小各不相等，是否可读也不相同，这里新创建一个目录用于存放statefulset所有的资源清单文件等

[root@k8s-master ~]# mkdir statefulset && cd statefulset

(1)编写创建pv的资源清单
[root@k8s-master statefulset]# vim pv-nfs.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs-001
  labels:
    name: pv001
spec:
  nfs:
    path: /data/volumes/v1
    server: 192.168.1.34
    readOnly: false 
  accessModes: ["ReadWriteOnce","ReadWriteMany"]
  capacity:
    storage: 5Gi
  persistentVolumeReclaimPolicy: Retain
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs-002
  labels:
    name: pv002
spec:
  nfs:
    path: /data/volumes/v2
    server: 192.168.1.34
    readOnly: false 
  accessModes: ["ReadWriteOnce"]
  capacity:
    storage: 5Gi
  persistentVolumeReclaimPolicy: Retain
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs-003
  labels:
    name: pv003
spec:
  nfs:
    path: /data/volumes/v3
    server: 192.168.1.34
    readOnly: false 
  accessModes: ["ReadWriteOnce","ReadWriteMany"]
  capacity:
    storage: 5Gi
  persistentVolumeReclaimPolicy: Retain
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs-004
  labels:
    name: pv004
spec:
  nfs:
    path: /data/volumes/v4
    server: 192.168.1.34
    readOnly: false 
  accessModes: ["ReadWriteOnce","ReadWriteMany"]
  capacity:
    storage: 5Gi
  persistentVolumeReclaimPolicy: Retain
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs-005
  labels:
    name: pv005
spec:
  nfs:
    path: /data/volumes/v5
    server: 192.168.1.34
    readOnly: false 
  accessModes: ["ReadWriteOnce","ReadWriteMany"]
  capacity:
    storage: 5Gi
  persistentVolumeReclaimPolicy: Retain

(2)创建PV
[root@k8s-master statefulset]# kubectl apply -f pv-nfs.yaml  
persistentvolume/pv-nfs-001 created
persistentvolume/pv-nfs-002 created
persistentvolume/pv-nfs-003 created
persistentvolume/pv-nfs-004 created
persistentvolume/pv-nfs-005 created

(3)查看PV
[root@k8s-master statefulset]# kubectl get pv 
NAME         CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS   REASON   AGE
pv-nfs-001   2Gi        RWO,RWX        Retain           Available                                   3s
pv-nfs-002   5Gi        RWO            Retain           Available                                   3s
pv-nfs-003   5Gi        RWO,RWX        Retain           Available                                   3s
pv-nfs-004   5Gi        RWO,RWX        Retain           Available                                   3s
pv-nfs-005   5Gi        RWO,RWX        Retain           Available                                   3s

3）编写定义StatefulSet的资源清单，首先我们要定义一个Headless Service，这里headless Service和StatefulSet写在一个文件。

[root@k8s-master statefulset]# vim statefulset-demo.yaml
#定义一个Headless Service
apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
  labels:
    app: nginx-svc
spec:
  ports:
  - name: http
    port: 80
  clusterIP: None
  selector:
    app: nginx-pod
---
#定义StatefulSet
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nginx-statefulset
spec:
  serviceName: nginx-svc    #指定service，和上面定义的service对应
  replicas: 5    #指定副本数量
  selector:    #指定标签选择器，和后面的pod的标签对应
    matchLabels:
      app: nginx-pod
  template:    #定义后端Pod的模板
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.12
        imagePullPolicy: IfNotPresent
        ports:
        - name: http
          containerPort: 80
        volumeMounts:
        - name: nginxdata
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:    #定义存储卷申请模板
  - metadata: 
      name: nginxdata
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 5Gi

#---
解析上面的资源清单：由于StatefulSet资源依赖于一个事先存在的Service资源，所以需要先定义一个名为nginx-svc的Headless Service资源，用于关联到每个Pod资源创建DNS资源记录。接着定义了一个名为nginx-statefulset的StatefulSet资源，它通过Pod模板创建了5个Pod资源副本，并基于volumeClaiTemplate向前面创建的PV进行了请求大小为5Gi的专用存储卷。

4）创建StatefulSet资源，这里打开另外一个窗口实时查看pod

[root@k8s-master statefulset]# kubectl apply -f statefulset-demo.yaml 
service/nginx-svc created
statefulset.apps/nginx-statefulset created

[root@k8s-master statefulset]# kubectl get svc   #查看创建的无头服务nginx-svc
NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   5d19h
nginx-svc    ClusterIP   None         <none>        80/TCP    29s

[root@k8s-master statefulset]# kubectl get pv     #查看PV绑定
NAME         CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                                   STORAGECLASS   REASON   AGE
pv-nfs-001   2Gi        RWO,RWX        Retain           Available                                                                   3m49s
pv-nfs-002   5Gi        RWO            Retain           Bound       default/nginxdata-nginx-statefulset-0                           3m49s
pv-nfs-003   5Gi        RWO,RWX        Retain           Bound       default/nginxdata-nginx-statefulset-1                           3m49s
pv-nfs-004   5Gi        RWO,RWX        Retain           Bound       default/nginxdata-nginx-statefulset-2                           3m49s
pv-nfs-005   5Gi        RWO,RWX        Retain           Available                                                                   3m48s
[root@k8s-master statefulset]# kubectl get pvc     #查看PVC绑定
NAME                            STATUS   VOLUME       CAPACITY   ACCESS MODES   STORAGECLASS   AGE
nginxdata-nginx-statefulset-0   Bound    pv-nfs-002   5Gi        RWO                           21s
nginxdata-nginx-statefulset-1   Bound    pv-nfs-003   5Gi        RWO,RWX                       18s
nginxdata-nginx-statefulset-2   Bound    pv-nfs-004   5Gi        RWO,RWX                       15s
[root@k8s-master statefulset]# kubectl get statefulset    #查看StatefulSet
NAME                READY   AGE
nginx-statefulset   3/3     58s

[root@k8s-master statefulset]# kubectl get pods    #查看Pod信息
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          78s
nginx-statefulset-1   1/1     Running   0          75s
nginx-statefulset-2   1/1     Running   0          72s


[root@k8s-master ~]# kubectl get pods -w    #动态查看pod创建过程，可以发现它是按照顺序从0-(n-1)的顺序创建
nginx-statefulset-0   0/1   Pending   0     0s
nginx-statefulset-0   0/1   Pending   0     0s
nginx-statefulset-0   0/1   Pending   0     1s
nginx-statefulset-0   0/1   ContainerCreating   0     1s
nginx-statefulset-0   1/1   Running             0     3s
nginx-statefulset-1   0/1   Pending             0     0s
nginx-statefulset-1   0/1   Pending             0     0s
nginx-statefulset-1   0/1   Pending             0     1s
nginx-statefulset-1   0/1   ContainerCreating   0     1s
nginx-statefulset-1   1/1   Running             0     3s
nginx-statefulset-2   0/1   Pending             0     0s
nginx-statefulset-2   0/1   Pending             0     0s
nginx-statefulset-2   0/1   Pending             0     2s
nginx-statefulset-2   0/1   ContainerCreating   0     2s
nginx-statefulset-2   1/1   Running             0     4s

5）删除测试，同样在另外一个窗口动态查看pod

[root@k8s-master statefulset]# kubectl delete -f statefulset-demo.yaml 
service "nginx-svc" deleted
statefulset.apps "nginx-statefulset" deleted

[root@k8s-master ~]# kubectl get pods -w     #动态查看删除过程，可以也是按照顺序删除，逆向关闭。
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          18m
nginx-statefulset-1   1/1     Running   0          18m
nginx-statefulset-2   1/1     Running   0          18m
nginx-statefulset-2   1/1     Terminating   0          18m
nginx-statefulset-0   1/1     Terminating   0          18m
nginx-statefulset-1   1/1     Terminating   0          18m
nginx-statefulset-2   0/1     Terminating   0          18m
nginx-statefulset-0   0/1     Terminating   0          18m
nginx-statefulset-1   0/1     Terminating   0          18m
nginx-statefulset-2   0/1     Terminating   0          18m
nginx-statefulset-2   0/1     Terminating   0          18m
nginx-statefulset-2   0/1     Terminating   0          18m
nginx-statefulset-1   0/1     Terminating   0          18m
nginx-statefulset-1   0/1     Terminating   0          18m
nginx-statefulset-0   0/1     Terminating   0          18m
nginx-statefulset-0   0/1     Terminating   0          18m


此时PVC依旧存在的，再重新创建pod时，依旧会重新去绑定原来的PVC
[root@k8s-master statefulset]# kubectl apply -f statefulset-demo.yaml 
service/nginx-svc created
statefulset.apps/nginx-statefulset created

[root@k8s-master statefulset]# kubectl get pvc     #查看PVC绑定
NAME                            STATUS   VOLUME       CAPACITY   ACCESS MODES   STORAGECLASS   AGE
nginxdata-nginx-statefulset-0   Bound    pv-nfs-002   5Gi        RWO                           30m
nginxdata-nginx-statefulset-1   Bound    pv-nfs-003   5Gi        RWO,RWX                       30m
nginxdata-nginx-statefulset-2   Bound    pv-nfs-004   5Gi        RWO,RWX                       30m

6）名称解析，在创建的每一个Pod中，每一个Pod自己的名称都是可以被解析的，如下：

[root@k8s-master statefulset]# kubectl get pods -o wide 
NAME                  READY   STATUS    RESTARTS   AGE   IP            NODE        NOMINATED NODE   READINESS GATES
nginx-statefulset-0   1/1     Running   0          12m   10.244.2.96   k8s-node2   <none>           <none>
nginx-statefulset-1   1/1     Running   0          12m   10.244.1.96   k8s-node1   <none>           <none>
nginx-statefulset-2   1/1     Running   0          12m   10.244.2.97   k8s-node2   <none>           <none>


[root@k8s-master statefulset]# dig -t A nginx-statefulset-0.nginx-svc.default.svc.cluster.local @10.96.0.10
......
;; ANSWER SECTION:
nginx-statefulset-0.nginx-svc.default.svc.cluster.local. 30 IN A 10.244.2.96

[root@k8s-master statefulset]# dig -t A nginx-statefulset-1.nginx-svc.default.svc.cluster.local @10.96.0.10
......
;; ANSWER SECTION:
nginx-statefulset-1.nginx-svc.default.svc.cluster.local. 30 IN A 10.244.1.96

[root@k8s-master statefulset]# dig -t A nginx-statefulset-2.nginx-svc.default.svc.cluster.local @10.96.0.10
......
;; ANSWER SECTION:
nginx-statefulset-2.nginx-svc.default.svc.cluster.local. 30 IN A 10.244.2.97

也可以进入到容器中进行解析，通过对Pod的名称解析得到IP
# pod_name.service_name.ns_name.svc.cluster.local
eg: nginx-statefulset-0.nginx-svc.default.svc.cluster.local

StatefulSet资源扩缩容

StatefulSet资源的扩缩容与Deployment资源相似，即通过修改资源的副本数来改动其目标Pod资源数量。对StatefulSet资源来说，kubectl scale和kubectl patch命令均可以实现此功能，也可以使用kubectl edit命令直接修改其副本数，或者修改资源清单文件，由kubectl apply命令重新声明。

1）通过scale将nginx-statefulset资源副本数量扩容为4个

[root@k8s-master statefulset]# kubectl scale statefulset/nginx-statefulset --replicas=4   #扩容副本增加到4个
statefulset.apps/nginx-statefulset scaled
[root@k8s-master statefulset]# kubectl get pods     #查看pv信息
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          16m
nginx-statefulset-1   1/1     Running   0          16m
nginx-statefulset-2   1/1     Running   0          16m
nginx-statefulset-3   1/1     Running   0          3s

[root@k8s-master statefulset]# kubectl get pv   #查看pv绑定
NAME         CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                                   STORAGECLASS   REASON   AGE
pv-nfs-001   2Gi        RWO,RWX        Retain           Available                                                                   21m
pv-nfs-002   5Gi        RWO            Retain           Bound       default/nginxdata-nginx-statefulset-0                           21m
pv-nfs-003   5Gi        RWO,RWX        Retain           Bound       default/nginxdata-nginx-statefulset-1                           21m
pv-nfs-004   5Gi        RWO,RWX        Retain           Bound       default/nginxdata-nginx-statefulset-2                           21m
pv-nfs-005   5Gi        RWO,RWX        Retain           Bound       default/nginxdata-nginx-statefulset-3                           21m

2）通过patch将nginx-statefulset资源副本数量缩容为3个

[root@k8s-master statefulset]# kubectl patch sts/nginx-statefulset -p '{"spec":{"replicas":2}}'    #通过patch打补丁方式缩容
statefulset.apps/nginx-statefulset patched

[root@k8s-master ~]# kubectl get pods -w    #动态查看缩容过程
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          17m
nginx-statefulset-1   1/1     Running   0          17m
nginx-statefulset-2   1/1     Running   0          17m
nginx-statefulset-3   1/1     Running   0          1m
nginx-statefulset-3   1/1     Terminating   0          20s
nginx-statefulset-3   0/1     Terminating   0          20s
nginx-statefulset-3   0/1     Terminating   0          22s
nginx-statefulset-3   0/1     Terminating   0          22s
nginx-statefulset-2   1/1     Terminating   0          24s
nginx-statefulset-2   0/1     Terminating   0          24s
nginx-statefulset-2   0/1     Terminating   0          36s
nginx-statefulset-2   0/1     Terminating   0          36s

更新策略

StatefulSet的默认更新策略为滚动更新，也可以暂停更新

滚动更新示例：

[root@k8s-master statefulset]# kubectl patch sts/nginx-statefulset -p '{"spec":{"replicas":4}}'    #这里先将副本扩容到4个。方便测试

[root@k8s-master ~]# kubectl set image statefulset nginx-statefulset nginx=nginx:1.14    #更新镜像版本
statefulset.apps/nginx-statefulset image updated

[root@k8s-master ~]# kubectl get pods -w    #动态查看更新
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          18m
nginx-statefulset-1   1/1     Running   0          18m
nginx-statefulset-2   1/1     Running   0          13m
nginx-statefulset-3   1/1     Running   0          13m
nginx-statefulset-3   1/1     Terminating   0          13m
nginx-statefulset-3   0/1     Terminating   0          13m
nginx-statefulset-3   0/1     Terminating   0          13m
nginx-statefulset-3   0/1     Terminating   0          13m
nginx-statefulset-3   0/1     Pending       0          0s
nginx-statefulset-3   0/1     Pending       0          0s
nginx-statefulset-3   0/1     ContainerCreating   0          0s
nginx-statefulset-3   1/1     Running             0          2s
nginx-statefulset-2   1/1     Terminating         0          13m
nginx-statefulset-2   0/1     Terminating         0          13m
nginx-statefulset-2   0/1     Terminating         0          14m
nginx-statefulset-2   0/1     Terminating         0          14m
nginx-statefulset-2   0/1     Pending             0          0s
nginx-statefulset-2   0/1     Pending             0          0s
nginx-statefulset-2   0/1     ContainerCreating   0          0s
nginx-statefulset-2   1/1     Running             0          1s
nginx-statefulset-1   1/1     Terminating         0          18m
nginx-statefulset-1   0/1     Terminating         0          18m
nginx-statefulset-1   0/1     Terminating         0          18m
nginx-statefulset-1   0/1     Terminating         0          18m
nginx-statefulset-1   0/1     Pending             0          0s
nginx-statefulset-1   0/1     Pending             0          0s
nginx-statefulset-1   0/1     ContainerCreating   0          0s
nginx-statefulset-1   1/1     Running             0          2s
nginx-statefulset-0   1/1     Terminating         0          18m
nginx-statefulset-0   0/1     Terminating         0          18m
nginx-statefulset-0   0/1     Terminating         0          18m
nginx-statefulset-0   0/1     Terminating         0          18m
nginx-statefulset-0   0/1     Pending             0          0s
nginx-statefulset-0   0/1     Pending             0          0s
nginx-statefulset-0   0/1     ContainerCreating   0          0s
nginx-statefulset-0   1/1     Running             0          2s

[root@k8s-master statefulset]# kubectl get pods -l app=nginx-pod -o custom-columns=NAME:metadata.name,IMAGE:spec.containers[0].image    #查看更新完成后的镜像版本
NAME                  IMAGE
nginx-statefulset-0   nginx:1.14
nginx-statefulset-1   nginx:1.14
nginx-statefulset-2   nginx:1.14
nginx-statefulset-3   nginx:1.14   

通过上面示例可以看出，默认为滚动更新，倒序更新，更新完成一个接着更新下一个。

暂停更新示例

有时候设定了一个更新操作，但是又不希望一次性全部更新完成，想先更新几个，观察其是否稳定，然后再更新所有的。这时候只需要将.spec.spec.updateStrategy.rollingUpdate.partition字段的值进行修改即可。（默认值为0，所以我们看到了更新效果为上面那样，全部更新）。该字段表示如果设置为2，那么只有当编号大于等于2的才会进行更新。类似于金丝雀的发布方式。示例如下：

[root@k8s-master ~]# kubectl patch sts/nginx-statefulset -p '{"spec":{"updateStrategy":{"rollingUpdate":{"partition":2}}}}}'     #将更新值partition设置为2
statefulset.apps/nginx-statefulset patched

[root@k8s-master ~]# kubectl set image statefulset nginx-statefulset nginx=nginx:1.12    #更新镜像版本
statefulset.apps/nginx-statefulset image updated

[root@k8s-master ~]# kubectl get pods -w     #动态查看更新
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          11m
nginx-statefulset-1   1/1     Running   0          11m
nginx-statefulset-2   1/1     Running   0          11m
nginx-statefulset-3   1/1     Running   0          11m
nginx-statefulset-3   1/1     Terminating   0          12m
nginx-statefulset-3   0/1     Terminating   0          12m
nginx-statefulset-3   0/1     Terminating   0          12m
nginx-statefulset-3   0/1     Terminating   0          12m
nginx-statefulset-3   0/1     Pending       0          0s
nginx-statefulset-3   0/1     Pending       0          0s
nginx-statefulset-3   0/1     ContainerCreating   0          0s
nginx-statefulset-3   1/1     Running             0          2s
nginx-statefulset-2   1/1     Terminating         0          11m
nginx-statefulset-2   0/1     Terminating         0          11m
nginx-statefulset-2   0/1     Terminating         0          12m
nginx-statefulset-2   0/1     Terminating         0          12m
nginx-statefulset-2   0/1     Pending             0          0s
nginx-statefulset-2   0/1     Pending             0          0s
nginx-statefulset-2   0/1     ContainerCreating   0          0s
nginx-statefulset-2   1/1     Running             0          2s

[root@k8s-master statefulset]# kubectl get pods -l app=nginx-pod -o custom-columns=NAME:metadata.name,IMAGE:spec.containers[0].image    #查看更新完成后的镜像版本，可以发现只有当编号大于等于2的进行了更新。
NAME                  IMAGE
nginx-statefulset-0   nginx:1.14
nginx-statefulset-1   nginx:1.14
nginx-statefulset-2   nginx:1.12
nginx-statefulset-3   nginx:1.12



将剩余的也全部更新，只需要将更新策略的partition的值改为0即可，如下：
[root@k8s-master ~]# kubectl patch sts/nginx-statefulset -p '{"spec":{"updateStrategy":{"rollingUpdate":{"partition":0}}}}}'    #将更新值partition设置为0
statefulset.apps/nginx-statefulset patche
[root@k8s-master ~]# kubectl get pods -w    #动态查看更新
NAME                  READY   STATUS    RESTARTS   AGE
nginx-statefulset-0   1/1     Running   0          18m
nginx-statefulset-1   1/1     Running   0          18m
nginx-statefulset-2   1/1     Running   0          6m44s
nginx-statefulset-3   1/1     Running   0          6m59s
nginx-statefulset-1   1/1     Terminating   0          19m
nginx-statefulset-1   0/1     Terminating   0          19m
nginx-statefulset-1   0/1     Terminating   0          19m
nginx-statefulset-1   0/1     Terminating   0          19m
nginx-statefulset-1   0/1     Pending       0          0s
nginx-statefulset-1   0/1     Pending       0          0s
nginx-statefulset-1   0/1     ContainerCreating   0          0s
nginx-statefulset-1   1/1     Running             0          2s
nginx-statefulset-0   1/1     Terminating         0          19m
nginx-statefulset-0   0/1     Terminating         0          19m
nginx-statefulset-0   0/1     Terminating         0          19m
nginx-statefulset-0   0/1     Terminating         0          19m
nginx-statefulset-0   0/1     Pending             0          0s
nginx-statefulset-0   0/1     Pending             0          0s
nginx-statefulset-0   0/1     ContainerCreating   0          0s
nginx-statefulset-0   1/1     Running             0          2s