实践

（1）部署三个副本应用，初始镜像为httpd:2.2.31，然后将其更新到httpd:2.2.32，httpd:2.2.31的配置文件如下：

apiVersion: apps/v1
kind: Deployment
metadata:name: httpd-deployment
spec:replicas: 3selector:matchLabels:app: httpdtemplate:metadata:labels:app: httpd # 这里是为Pod分配的标签spec:containers:- name: httpdimage: httpd:2.2.31ports:- containerPort: 80

（2）通过apply部署

zy@k8s-master:~$ kubectl apply -f httpd.yml 
deployment.apps/httpd-deployment created

（3）查看http-deployment

zy@k8s-master:~$ kubectl get deployments.apps httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     3            3           9m47s   httpd        httpd:2.2.31   app=httpd

（4）将版本从31改成32重新apply

zy@k8s-master:~$ kubectl get deployments.apps httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     1            3           16m   httpd        httpd:2.2.32   app=httpd

（5）查看replicaset

可以看到之前的 httpd-deployment-6b96d79d79 的三个httpd:2.2.31 pod 已经被 httpd-deployment-7d98db6f46 的三个httpd:2.2.32 pod 替换了。

zy@k8s-master:~$ kubectl get replicaset -o wide
NAME                          DESIRED   CURRENT   READY   AGE     CONTAINERS   IMAGES         SELECTOR
httpd-deployment-6b96d79d79   0         0         0       21m     httpd        httpd:2.2.31   app=httpd,pod-template-hash=6b96d79d79
httpd-deployment-7d98db6f46   3         3         3       5m32s   httpd        httpd:2.2.32   app=httpd,pod-template-hash=7d98db6f46

回滚

        kubectl apply每次更新应用时，k8s都会记录下当前的配置，保存为一个版本，这样就可以回滚到某个特定的revision。

        默认配置下，k8s只会保留最近的几个版本，可以在deployment的配置文件中通过revisonHistoryLimit属性增加revision数量。

实践：

（1）写三个配置文件：

httpd.yml对应2.4.16 

httpd1.yml对应2.4.17 

httpd2.yml对应2.4.18

zy@k8s-master:~$ cat httpd.yml 
apiVersion: apps/v1
kind: Deployment
metadata:name: httpd-deployment
spec:replicas: 3selector:matchLabels:app: httpdtemplate:metadata:labels:app: httpd # 这里是为Pod分配的标签spec:containers:- name: httpdimage: httpd:2.4.16ports:- containerPort: 80

（2）apply应用

--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一个revision对应的是哪个配置文件了

zy@k8s-master:~$ kubectl apply -f httpd.yml --record
deployment.apps/httpd-deployment configured
zy@k8s-master:~$ kubectl get deployment httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     1            3           32m   httpd        httpd:2.4.16   app=httpd
zy@k8s-master:~$ kubectl apply -f httpd1.yml --record
deployment.apps/httpd-deployment configured
zy@k8s-master:~$ kubectl get deployment httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     1            3           33m   httpd        httpd:2.4.17   app=httpd
zy@k8s-master:~$ kubectl apply -f httpd2.yml --record
deployment.apps/httpd-deployment configured
zy@k8s-master:~$ kubectl get deployment httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     1            3           33m   httpd        httpd:2.4.18   app=httpd

（3）通过 kubectl rollout history deployment httpd-deployment 查看revison历史记录：

REVISION  CHANGE-CAUSE
1         
2         
3         kubectl apply --filename=httpd.yml --record=true
4         kubectl apply --filename=httpd1.yml --record=true
5         kubectl apply --filename=httpd2.yml --record=true

CHANGE-CAUSE就是 --record 的结果。

（4）如果要回滚到某个版本，比如 revision3，可以执行命令kubectl rollout undo deployment httpd-deployment --to-revision=3

可以看到版本又回到了 2.4.16

zy@k8s-master:~$ kubectl rollout undo deployment httpd-deployment --to-revision=3
deployment.apps/httpd-deployment rolled backzy@k8s-master:~$ kubectl get deployment httpd-deployment -o wide
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
httpd-deployment   3/3     3            3           40m   httpd        httpd:2.4.16   app=httpd

（5）此时，revision的历史记录也会发生变化

revision3 变成了 revision6。

zy@k8s-master:~$ kubectl rollout history deployment httpd-deployment 
deployment.apps/httpd-deployment 
REVISION  CHANGE-CAUSE
1         
2         
4         kubectl apply --filename=httpd1.yml --record=true
5         kubectl apply --filename=httpd2.yml --record=true
6         kubectl apply --filename=httpd.yml --record=true