再赶快查看一下滚动发布的状态：
$ kubectl rollout status deployment my-first-demo-dep Waiting for rollout to finish: 1 old replicas are pending termination... deployment "my-first-demo-dep" successfully rolled out如上命令所表示，随着最后一个old replicas 终止，新版本的deployment成功发布了successfully rolled out。
简直是太激动了，验证一下是不是3个pod，如下，没问题，3个Running状态。
$ kubectl get pods NAME READY STATUS RESTARTS AGE my-first-demo-dep-54596847d8-6m4n9 1/1 Running 0 36s my-first-demo-dep-54596847d8-jrm8g 1/1 Running 0 38s my-first-demo-dep-54596847d8-nqgmn 1/1 Running 0 34s访问一下看看：
$ curl 'http://localhost:30000/' <h1>Hello worldls , this is Version 2.</h1>已经是新版本了，可惜啊，新版本有问题啊！单词拼错了，world写成了worldls，我们来赶紧回滚一下。
Kubenetes应用集群回滚上面我们使用滚动发布，将网站升级为version2了。但是有错误，我们来查看一下发布历史：
$ kubectl rollout history deployment my-first-demo-dep deployment.extensions/my-first-demo-dep REVISION CHANGE-CAUSE 1 kubectl apply --filename=dep.yml --record=true 2 kubectl apply --filename=dep.yml --record=true可以看到，有两个版本，我们回滚到版本1，执行如下命令：
$ kubectl rollout undo deployment my-first-demo-dep --to-revision=1 deployment.extensions/my-first-demo-dep rolled back查看回滚过程状态：
$ kubectl rollout status deployment my-first-demo-dep Waiting for deployment "my-first-demo-dep" rollout to finish: 2 out of 3 new replicas have been updated... Waiting for deployment "my-first-demo-dep" rollout to finish: 2 out of 3 new replicas have been updated... Waiting for deployment "my-first-demo-dep" rollout to finish: 2 out of 3 new replicas have been updated... Waiting for deployment "my-first-demo-dep" rollout to finish: 1 old replicas are pending termination... Waiting for deployment "my-first-demo-dep" rollout to finish: 1 old replicas are pending termination... deployment "my-first-demo-dep" successfully rolled out上面的日志显示了完整的回滚过程，看到最后一行successfully rolled out输出的时候，说明回滚完成了。这时候响应的应该就是 Hello world!,我们来验证一下回滚效果：
$ curl 'http://localhost:30000/' <h1>Hello world! <h1>OK，成功了，回滚到了没有错误的原始版本。
总结本篇演示了Kubenetes集群发布，集群副本集查看，集群自愈能力演示，集群扩容，滚动升级，以及回滚。然而这一切来得是如此的简单，我们只需要修改一下配置，执行一个命令，剩下的工作Kubenetes都帮我们做了。当我在回顾我几年前所在的某家公司的时候，程序升级上线都是由运维手工完成，虽然也完成了任务，但是那种原始的操作方式，在时下如果还有人用的话，那简直是不敢想象。
Docker & k8s 系列一：快速上手docker
Docker & k8s 系列二：本机k8s环境搭建
Docker & k8s 系列三：在k8s中部署单个服务实例