Pod滚动更新与回滚

1.场景

应用两个配置文件deploy-nginx-v1.yaml、deploy-nginx-v2.yaml，nginx镜像分别为1.16.1与latest。

2.实验

应用配置文件deploy-nginx-v1.yaml。

fxx2@kube-node-1:~/yaml$ kubectl apply -f deploy-nginx-v1.yaml
deployment.apps/nginx-deploy created
fxx2@kube-node-1:~/yaml$ kubectl get rs -o wide
NAME                      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES         SELECTOR
nginx-deploy-848ff6b4cf   2         2         0       6s    nginx        nginx:1.16.1   app=web_server,pod-template-hash=848ff6b4cf
fxx2@kube-node-1:~/yaml$

应用配置文件deploy-nginx-v2.yaml，将nginx版本升级为latest。

fxx2@kube-node-1:~/yaml$ kubectl apply -f deploy-nginx-v2.yaml
deployment.apps/nginx-deploy configured
fxx2@kube-node-1:~/yaml$ kubectl get rs -o wide
NAME                      DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES         SELECTOR
nginx-deploy-749bb6d465   2         2         2       4s      nginx        nginx:latest   app=web_server,pod-template-hash=749bb6d465
nginx-deploy-848ff6b4cf   0         0         0       3m27s   nginx        nginx:1.16.1   app=web_server,pod-template-hash=848ff6b4cf
fxx2@kube-node-1:~/yaml$ kubectl get pod
NAME                            READY   STATUS        RESTARTS   AGE
nginx-deploy-749bb6d465-nl72r   1/1     Running       0          3m52s
nginx-deploy-749bb6d465-qzsv4   1/1     Running       0          3m47s

可以看到发生如下变化：
新创建的RS：nginx-deploy-749bb6d465，镜像为latest，并且管理了两个pod。
旧RS：nginx-deploy-848ff6b4cf，已经没有pod。

fxx2@kube-node-1:~/yaml$ kubectl describe deploy nginx-deploy
....
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deploy-749bb6d465 (2/2 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  20m   deployment-controller  Scaled up replica set nginx-deploy-848ff6b4cf to 2
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled up replica set nginx-deploy-749bb6d465 to 1
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled down replica set nginx-deploy-848ff6b4cf to 1
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled up replica set nginx-deploy-749bb6d465 to 2
  Normal  ScalingReplicaSet  17m   deployment-controller  Scaled down replica set nginx-deploy-848ff6b4cf to 0
fxx2@kube-node-1:~/yaml$

3.回滚

使用kubectl rollout history可以查看变动的版次（revision）,可以使用revisionHistoryLimit属性设定revision的数量。

fxx2@kube-node-1:~/yaml$ kubectl rollout history deployment nginx-deploy
deployment.apps/nginx-deploy
REVISION  CHANGE-CAUSE     
1         <none>
2         <none>

上面CHANGE-CAUSE记录值为空，回滚时不方便确定配置文件，可以使用–record参数记录，下面重新开始测试：

fxx2@kube-node-1:~/yaml$ kubectl apply -f deploy-nginx-v1.yaml --record
deployment.apps/nginx-deploy created
fxx2@kube-node-1:~/yaml$
fxx2@kube-node-1:~/yaml$ kubectl get rs -o wide
NAME                      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES         SELECTOR
nginx-deploy-848ff6b4cf   2         2         2       20s   nginx        nginx:1.16.1   app=web_server,pod-template-hash=848ff6b4cf
fxx2@kube-node-1:~/yaml$ kubectl apply -f deploy-nginx-v2.yaml --record
deployment.apps/nginx-deploy configured
fxx2@kube-node-1:~/yaml$
fxx2@kube-node-1:~/yaml$ kubectl get rs -o wide
NAME                      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES         SELECTOR
nginx-deploy-749bb6d465   2         2         2       12s   nginx        nginx:latest   app=web_server,pod-template-hash=749bb6d465
nginx-deploy-848ff6b4cf   0         0         0       39s   nginx        nginx:1.16.1   app=web_server,pod-template-hash=848ff6b4cf

fxx2@kube-node-1:~/yaml$ kubectl rollout history deployment nginx-deploy
deployment.apps/nginx-deploy
REVISION CHANGE-CAUSE
1 kubectl apply --filename=deploy-nginx-v1.yaml --record=true
2 kubectl apply --filename=deploy-nginx-v2.yaml --record=true

fxx2@kube-node-1:~/yaml$ kubectl get pod -o wide
NAME                            READY   STATUS        RESTARTS   AGE     IP             NODE          NOMINATED NODE   READINESS GATES
nginx-deploy-749bb6d465-fx2r7   1/1     Running       0          4m11s   10.244.0.249   kube-node-1   <none>           <none>
nginx-deploy-749bb6d465-vlvcc   1/1     Running       0          4m16s   10.244.0.248   kube-node-1   <none>           <none>
fxx2@kube-node-1:~/yaml$

回滚至nginx1.16.1版本

fxx2@kube-node-1:~/yaml$ kubectl rollout undo deployment nginx-deploy --to-revision=1
deployment.apps/nginx-deploy rolled back
fxx2@kube-node-1:~/yaml$ kubectl get rs -o wide
NAME                      DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES         SELECTOR
nginx-deploy-749bb6d465   0         0         0       7m2s    nginx        nginx:latest   app=web_server,pod-template-hash=749bb6d465
nginx-deploy-848ff6b4cf   2         2         2       7m29s   nginx        nginx:1.16.1   app=web_server,pod-template-hash=848ff6b4cf
fxx2@kube-node-1:~/yaml$ kubectl get pod -o wide
NAME                            READY   STATUS        RESTARTS   AGE   IP             NODE          NOMINATED NODE   READINESS GATES
nginx-deploy-848ff6b4cf-8lz4l   1/1     Running       0          27s   10.244.0.250   kube-node-1   <none>           <none>
nginx-deploy-848ff6b4cf-gnd7t   1/1     Running       0          21s   10.244.0.251   kube-node-1   <none>           <none>​