Rolling Update 滚动更新

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更新

** 7.1 practice

evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd   2/3     3            2           68s   httpd        httpd:2.2.31   run=httpd
evan@k8s-master:~$ kubectl  get pod 
\NAME                            READY   STATUS             RESTARTS   AGE
httpd-5ddb558f47-2pmhw          1/1     Running            0          78s
httpd-5ddb558f47-rwbhc          1/1     Running            0          78s
httpd-5ddb558f47-xtfb2          0/1     ImagePullBackOff   0          78s

evan@k8s-master:~$ kubectl  get pod 
NAME                            READY   STATUS             RESTARTS   AGE
httpd-5ddb558f47-2pmhw          1/1     Running            0          12m
httpd-5ddb558f47-rwbhc          1/1     Running            0          12m
httpd-5ddb558f47-xtfb2          1/1     Running            0          12m

evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd   3/3     3            3           12m   httpd        httpd:2.2.31   run=httpd


evan@k8s-master:~$ kubectl get replicaset -o wide 
NAME               DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-5ddb558f47   3         3         3       13m   httpd        httpd:2.2.31   pod-template-hash=5ddb558f47,run=httpd

将配置文件中 httpd:2.2.31 替换为 httpd:2.2.32，再次执行 kubectl apply

 ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  16m   deployment-controller  Scaled up replica set httpd-5ddb558f47 to 3
  Normal  ScalingReplicaSet  99s   deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 1
  Normal  ScalingReplicaSet  99s   deployment-controller  Scaled down replica set httpd-5ddb558f47 to 2
  Normal  ScalingReplicaSet  98s   deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 2
  Normal  ScalingReplicaSet  6s    deployment-controller  Scaled down replica set httpd-5ddb558f47 to 1
  Normal  ScalingReplicaSet  6s    deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 3


 ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  16m   deployment-controller  Scaled up replica set httpd-5ddb558f47 to 3
  Normal  ScalingReplicaSet  99s   deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 1
  Normal  ScalingReplicaSet  99s   deployment-controller  Scaled down replica set httpd-5ddb558f47 to 2
  Normal  ScalingReplicaSet  98s   deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 2
  Normal  ScalingReplicaSet  6s    deployment-controller  Scaled down replica set httpd-5ddb558f47 to 1
  Normal  ScalingReplicaSet  6s    deployment-controller  Scaled up replica set httpd-8bdffc6d8 to 3

回滚

** 7.2 回滚
ubectl apply 每次更新应用时 Kubernetes 都会记录下当前的配置，保存为一个 revision（版次），这样就可以回滚到某个特定 revision。

默认配置下，Kubernetes 只会保留最近的几个 revision，可以在 Deployment 配置文件中通过 revisionHistoryLimit 属性增加 revision 数量。

下面实践回滚功能。应用有如下三个配置文件 httpd.v1.yml，httpd.v2.yml 和 httpd.v3.yml，分别对应不同的 httpd 镜像 2.4.16，2.4.17 和 2.4.18：

evan@k8s-master:~$ kubectl  apply -f httpd.v1.yml --record 
deployment.extensions/httpd created
evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd   0/3     3            0           3s    httpd        httpd:2.4.16   run=httpd
evan@k8s-master:~$ kubectl  apply -f httpd.v2.yml --record 
deployment.extensions/httpd configured
evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd   0/3     2            0           30s   httpd        httpd:2.4.18   run=httpd
evan@k8s-master:~$ kubectl  apply -f httpd.v3.yml --record 
deployment.extensions/httpd configured
evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd   0/3     2            0           39s   httpd        httpd:2.4.18   run=httpd

--record 的作用是将当前命令记录到 revision 记录中，这样我们就可以知道每个 revison 对应的是哪个配置文件。通过 kubectl rollout history deployment httpd 查看 revison 历史记录

evan@k8s-master:~$ kubectl rollout history deployment httpd
deployment.extensions/httpd 
REVISION  CHANGE-CAUSE
1         kubectl apply --filename=httpd.v1.yml --record=true
2         kubectl apply --filename=httpd.v3.yml --record=true
3         kubectl apply --filename=httpd.v2.yml --record=true


evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE    CONTAINERS   IMAGES         SELECTOR
httpd   2/3     2            2           3m9s   httpd        httpd:2.4.17   run=httpd

evan@k8s-master:~$ kubectl rollout undo deployment httpd --to-revision=1
deployment.extensions/httpd rolled back
evan@k8s-master:~$ kubectl  get deployment httpd -o wide 
NAME    READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS   IMAGES         SELECTOR
httpd   2/3     3            2           3m36s   httpd        httpd:2.4.16   run=httpd

evan@k8s-master:~$ kubectl rollout history deployment httpd
deployment.extensions/httpd 
REVISION  CHANGE-CAUSE
2         kubectl apply --filename=httpd.v3.yml --record=true
3         kubectl apply --filename=httpd.v2.yml --record=true
4         kubectl apply --filename=httpd.v1.yml --record=true

see also

https://www.cnblogs.com/CloudMan6/p/8543006.html

https://www.cnblogs.com/CloudMan6/p/8553331.html

检索自“https://wiki.linuxsa.org/index.php?title=Rolling_Update_滚动更新&oldid=944”