# Deployment Rollback

* 透過 deployment 建立的物件除了可以 rolling upgrade，也可以 rollback 到最先前的版本
* `--record` 會記錄 deployment 的每一次更新

# 建立 nginx:1.14.2 版本
$ kubectl apply -f https://k8s.io/examples/controllers/nginx-deployment.yaml --record=true

$ kubectl get po
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-85996f8dbd-rxcjn   1/1     Running   0          111s
nginx-deployment-85996f8dbd-w6265   1/1     Running   0          111s
nginx-deployment-85996f8dbd-ws9lq   1/1     Running   0          111s

$ kubectl describe deploy nginx-deployment
......
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx:1.14.2
    Port:         80/TCP
    Host Port:    0/TCP
......

* 更新 image 到 nginx:1.16.1 版本

$ kubectl set image deployment/nginx-deployment --record nginx=nginx:1.16.1
deployment.apps/nginx-deployment image updated

* 查看部署狀態

$ kubectl rollout status deployment/nginx-deployment
deployment "nginx-deployment" successfully rolled out

* 可以看到 ReplicaSet 有兩個版本，分別是舊版跟新版
* 舊的 ReplicaSet 會縮減到 0 個副本

$ kubectl get all
NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx-deployment-66f8758855-527lh   1/1     Running   0          81s
pod/nginx-deployment-66f8758855-d5s2p   1/1     Running   0          51s
pod/nginx-deployment-66f8758855-gws2w   1/1     Running   0          67s

NAME                 TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
service/kubernetes   ClusterIP   10.43.0.1    <none>        443/TCP   103d

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   3/3     3            3           4m4s

NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-66f8758855   3         3         3       81s
replicaset.apps/nginx-deployment-85996f8dbd   0         0         0       4m4s

* 查看現有 deployment image 版本

$ kubectl describe deploy nginx-deployment
......
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx:1.16.1
    Port:         80/TCP
    Host Port:    0/TCP
......

* 修改一個錯誤的 image

$ kubectl set image deployment/nginx-deployment --record nginx=nginx:1.161
deployment.apps/nginx-deployment image updated

* 查看部署狀態會卡住

$ kubectl rollout status deployment/nginx-deployment
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...

* 查看修改 deployment 的歷史紀錄

$ kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
1         kubectl apply --filename=https://k8s.io/examples/controllers/nginx-deployment.yaml --record=true
2         kubectl set image deployment/nginx-deployment nginx=nginx:1.16.1 --record=true
3         kubectl set image deployment/nginx-deployment nginx=nginx:1.161 --record=true

* 查看使用 第一版 會修改 deployment 那些設定

$ kubectl rollout history deployment/nginx-deployment --revision=1
deployment.apps/nginx-deployment with revision #1
Pod Template:
  Labels:       app=nginx
        pod-template-hash=85996f8dbd
  Annotations:  kubernetes.io/change-cause: kubectl apply --filename=https://k8s.io/examples/controllers/nginx-deployment.yaml --record=true
  Containers:
   nginx:
    Image:      nginx:1.14.2
    Port:       80/TCP
    Host Port:  0/TCP
    Environment:        <none>
    Mounts:     <none>
  Volumes:      <none>

* 指定 rollback 到第一版

$ kubectl rollout undo deployment/nginx-deployment --to-revision=1
deployment.apps/nginx-deployment rolled back

* 確認 deployment 已回到第一版本

$ kubectl describe deploy nginx-deployment
........
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx:1.14.2
    Port:         80/TCP
    Host Port:    0/TCP
......