在默认的策略下，statefulset启停Pod都是按照顺序执行的，新建Pod按照序号从小到大进行，删除Pod从大到小进行，通常需要在Pod配置就绪性探针，严格保证次序。

[root@maxiaoke local-k8s-yaml]# kubectl -n apps patch sts nginx-web -p '{"spec":{"replicas":5}}'  # 增加副本数
[root@maxiaoke ~]# kubectl get pod -n apps -w  # 观察启动顺序，前一个就绪后，再启动下一个
NAME          READY   STATUS    RESTARTS   AGE
nginx-web-0   1/1     Running   2          10h
nginx-web-1   1/1     Running   2          10h
nginx-web-2   0/1     Pending   0          0s
nginx-web-2   0/1     Pending   0          0s
nginx-web-2   0/1     Pending   0          1s
nginx-web-2   0/1     ContainerCreating   0          2s
nginx-web-2   0/1     Running             0          3s
nginx-web-2   1/1     Running             0          5s
nginx-web-3   0/1     Pending             0          0s
nginx-web-3   0/1     Pending             0          0s
nginx-web-3   0/1     Pending             0          1s
nginx-web-3   0/1     ContainerCreating   0          2s
nginx-web-3   0/1     Running             0          3s
nginx-web-3   1/1     Running             0          9s
nginx-web-4   0/1     Pending             0          0s
nginx-web-4   0/1     Pending             0          0s
nginx-web-4   0/1     Pending             0          1s
nginx-web-4   0/1     ContainerCreating   0          2s
nginx-web-4   0/1     Running             0          3s
nginx-web-4   1/1     Running             0          7s

[root@maxiaoke local-k8s-yaml]# kubectl -n apps patch sts nginx-web -p '{"spec":{"replicas":2}}' # 减少副本数
[root@maxiaoke ~]# kubectl get pod -n apps -w   # 观察停止顺序，按序号倒序停止
NAME          READY   STATUS    RESTARTS   AGE
nginx-web-0   1/1     Running   2          10h
nginx-web-1   1/1     Running   2          10h
nginx-web-2   1/1     Running   0          117s
nginx-web-3   1/1     Running   0          112s
nginx-web-4   1/1     Running   0          103s
nginx-web-4   1/1     Terminating   0          109s
nginx-web-4   0/1     Terminating   0          110s
nginx-web-4   0/1     Terminating   0          111s
nginx-web-4   0/1     Terminating   0          111s
nginx-web-4   0/1     Terminating   0          111s
nginx-web-3   1/1     Terminating   0          2m
nginx-web-3   0/1     Terminating   0          2m
nginx-web-3   0/1     Terminating   0          2m1s
nginx-web-3   0/1     Terminating   0          2m1s
nginx-web-2   1/1     Terminating   0          2m7s
nginx-web-2   0/1     Terminating   0          2m7s
nginx-web-2   0/1     Terminating   0          2m13s
nginx-web-2   0/1     Terminating   0          2m13s