Kubernetes基础：滚动升级回滚：rolling-update之rollback

灰太狼 2023-07-03 12:29 10阅读 0赞

上篇文章介绍了在RC中的滚动升级，这篇继续介绍RC中回滚的方式。

# RC滚动升级 #

可参看如下内容：[https://liumiaocn.blog.csdn.net/article/details/104205298][https_liumiaocn.blog.csdn.net_article_details_104205298]

# 回滚：rollback #

回滚使用如下命令即可：

> 执行命令：kubectl rolling-update busybox-rc -f v2.yaml --rollback

*  注意事项：回滚的是正在执行的滚动升级

非执行中的话则会提示类似如下的错误信息：

[root@host131 RollingUpdate]# kubectl rolling-update busybox-rc busybox-rc-v2 --rollback
    Command "rolling-update" is deprecated, use "rollout" instead
    Error from server (NotFound): replicationcontrollers "busybox-rc" not found
    [root@host131 RollingUpdate]#

# 事前准备 #

[root@host131 RollingUpdate]# kubectl create -f v1.yaml 
    replicationcontroller/busybox-rc-v1 created
    [root@host131 RollingUpdate]# 
    [root@host131 RollingUpdate]# kubectl get rc -o wide
    NAME            DESIRED   CURRENT   READY   AGE   CONTAINERS     IMAGES           SELECTOR
    busybox-rc-v1   3         3         3       9s    busybox-host   busybox:latest   app=busybox-v1
    [root@host131 RollingUpdate]# 
    [root@host131 RollingUpdate]# kubectl get pods -o wide
    NAME                  READY   STATUS    RESTARTS   AGE   IP              NODE              NOMINATED NODE   READINESS GATES
    busybox-rc-v1-dvlsw   1/1     Running   0          17s   10.254.152.7    192.168.163.131   <none>           <none>
    busybox-rc-v1-khc8t   1/1     Running   0          17s   10.254.152.10   192.168.163.131   <none>           <none>
    busybox-rc-v1-wd8rk   1/1     Running   0          17s   10.254.152.6    192.168.163.131   <none>           <none>
    [root@host131 RollingUpdate]# 
    [root@host131 RollingUpdate]# kubectl exec -it busybox-rc-v1-dvlsw sh 
    / # ps -ef
    PID   USER     TIME  COMMAND
        1 root      0:00 sleep 1000
        6 root      0:00 sh
       11 root      0:00 ps -ef
    / #

执行滚动升级

在上述执行的过程中，执行回滚操作，日志如下所示：

[root@host131 RollingUpdate]# kubectl rolling-update busybox-rc-v1 busybox-rc-v2 --rollback
    Command "rolling-update" is deprecated, use "rollout" instead
    Setting "busybox-rc-v1" replicas to 3
    Continuing update with existing controller busybox-rc-v1.
    Scaling up busybox-rc-v1 from 3 to 3, scaling down busybox-rc-v2 from 1 to 0 (keep 3 pods available, don't exceed 4 pods)

从提示中可以看到，希望做的事情是对的，将已经启动的busybox-rc-v2的Pod实例从1降到0，确认此时RC状态

[root@host131 test]# kubectl get rc -o wide
    NAME            DESIRED   CURRENT   READY   AGE     CONTAINERS     IMAGES           SELECTOR
    busybox-rc-v1   3         3         3       2m36s   busybox-host   busybox:latest   app=busybox-v1
    busybox-rc-v2   1         1         1       32s     busybox-host   busybox:latest   app=busybox-v2
    [root@host131 test]#

之后滚动升级窗口最终日志如下所示：

[root@host131 RollingUpdate]# kubectl rolling-update busybox-rc-v1 -f v2.yaml
    Command "rolling-update" is deprecated, use "rollout" instead
    Created busybox-rc-v2
    Scaling up busybox-rc-v2 from 0 to 3, scaling down busybox-rc-v1 from 3 to 0 (keep 3 pods available, don't exceed 4 pods)
    Scaling busybox-rc-v2 up to 1
    Scaling busybox-rc-v1 down to 2
    Scaling busybox-rc-v2 up to 2
    Scaling busybox-rc-v1 down to 1
    Scaling busybox-rc-v2 up to 3
    Scaling busybox-rc-v1 down to 0
    Update succeeded. Deleting old controller: busybox-rc-v1
    Renaming busybox-rc-v2 to busybox-rc-v1
    replicationcontroller/busybox-rc-v1 rolling updated
    [root@host131 RollingUpdate]#

可以看到滚动升级成功执行，但滚动升级的回滚没有成功，这并不是期待的结果

而且确认Pod状况，验证了Pod已经成功滚动，回滚并未发生

[root@host131 test]# kubectl get rc -o wide
    NAME            DESIRED   CURRENT   READY   AGE   CONTAINERS     IMAGES           SELECTOR
    busybox-rc-v1   3         3         3       2m    busybox-host   busybox:latest   app=busybox-v2
    [root@host131 test]# kubectl get pod -o wide
    NAME                  READY   STATUS    RESTARTS   AGE     IP             NODE              NOMINATED NODE   READINESS GATES
    busybox-rc-v2-cjp8n   1/1     Running   0          3m34s   10.254.152.6   192.168.163.131   <none>           <none>
    busybox-rc-v2-dvvxd   1/1     Running   0          4m40s   10.254.152.8   192.168.163.131   <none>           <none>
    busybox-rc-v2-lxwg5   1/1     Running   0          5m46s   10.254.152.5   192.168.163.131   <none>           <none>
    [root@host131 test]# kubectl exec -it busybox-rc-v2-cjp8n sh
    / # ps -ef
    PID   USER     TIME  COMMAND
        1 root      0:00 sleep 10000
        6 root      0:00 sh
       11 root      0:00 ps -ef
    / #

由于RC已经是一个过时很久的功能，此处主要是用于记录一下这种执行方式，回滚功能的验证会在后续Deployment进行详细的说明。

# 使用的YAML文件 #

[root@host131 RollingUpdate]# cat v1.yaml 
    ---
    apiVersion: v1
    kind: ReplicationController
    metadata:
      name: busybox-rc-v1
    spec:
      replicas: 3
      selector:
        app: busybox-v1
      template:
        metadata:
          labels:
            app: busybox-v1
        spec:
          containers:
          - name: busybox-host
            image: busybox:latest
            command: ["sleep"]
            args: ["1000"]
    ...
    [root@host131 RollingUpdate]# cat v2.yaml 
    ---
    apiVersion: v1
    kind: ReplicationController
    metadata:
      name: busybox-rc-v2
    spec:
      replicas: 3
      selector:
        app: busybox-v2
      template:
        metadata:
          labels:
            app: busybox-v2
        spec:
          containers:
          - name: busybox-host
            image: busybox:latest
            command: ["sleep"]
            args: ["10000"]
    ...
    [root@host131 RollingUpdate]#

# 参考内容 #

https://v1-14.docs.kubernetes.io/docs/reference/kubectl/cheatsheet/

[https_liumiaocn.blog.csdn.net_article_details_104205298]: https://liumiaocn.blog.csdn.net/article/details/104205298