随着Kubernetes的进一步深入使用，我们越来越体会到它给我们的工作带来的高效与便利。Rolling Update是Kubernetes系统中的一个强大的功能，能够为我们的运维工作带来极大的便利。
二.步骤
2.1 部署最初始版本Deployment。
初始Deployment的YAML如下：
apiVersion: apps/v1beta1kind: Deploymentmetadata: ?name: deployment-rolloutspec: ?replicas: 4 ?template: ???metadata: ?????labels: ???????test: httpd ???spec: ?????containers: ?????- name: httpd-rollout-test ???????image: httpd:2.2.31 ???????ports: ???????- containerPort: 80执行命令：
[root@k8s-m ~]# kubectl get deployment -o wideNAME ????????????????DESIRED ??CURRENT ??UP-TO-DATE ??AVAILABLE ??AGE ???CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout ??4 ????????4 ????????4 ???????????4 ??????????107s ??httpd-rollout-test ??httpd:2.2.31 ??test=httpd[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ???CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-5fb9c69c5c ??4 ????????4 ????????4 ??????116s ??httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd2.2 将初始版本升级。
升级到2.4.31，YAML如下：
apiVersion: apps/v1beta1kind: Deploymentmetadata: ?name: deployment-rolloutspec: ?revisionHistoryLimit: 10 ?replicas: 4 ?template: ???metadata: ?????labels: ???????test: httpd ???spec: ?????containers: ?????- name: httpd-rollout-test ???????image: httpd:2.4.33 ???????ports: ???????- containerPort: 80执行命令：
[root@k8s-m ~]# kubectl apply -f Httpd-Deployment-rollout-v1.yamldeployment.apps/deployment-rollout configured[root@k8s-m ~]# kubectl get deployment -o wideNAME ????????????????DESIRED ??CURRENT ??UP-TO-DATE ??AVAILABLE ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout ??4 ????????5 ????????2 ???????????3 ??????????3m57s ??httpd-rollout-test ??httpd:2.4.33 ??test=httpd[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-54766f574f ??2 ????????2 ????????0 ??????93s ????httpd-rollout-test ??httpd:2.4.33 ??pod-template-hash=54766f574f,test=httpddeployment-rollout-5fb9c69c5c ??3 ????????3 ????????3 ??????4m12s ??httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd[root@k8s-m ~]# kubectl get pod -o wideNAME ?????????????????????????????????READY ??STATUS ?????????????RESTARTS ??AGE ????IP ????????????NODE ????NOMINATED NODEdeployment-rollout-54766f574f-668pc ??0/1 ????ContainerCreating ??0 ?????????114s ???<none> ????????k8s-n1 ??<none>deployment-rollout-54766f574f-ssz67 ??0/1 ????ContainerCreating ??0 ?????????115s ???<none> ????????k8s-n2 ??<none>deployment-rollout-5fb9c69c5c-m5dvs ??1/1 ????Running ????????????0 ?????????4m34s ??10.244.2.47 ???k8s-n2 ??<none>deployment-rollout-5fb9c69c5c-p9grr ??1/1 ????Running ????????????0 ?????????4m34s ??10.244.1.113 ??k8s-n1 ??<none>deployment-rollout-5fb9c69c5c-tzm7w ??1/1 ????Running ????????????0 ?????????4m34s ??10.244.2.48 ???k8s-n2 ??<none>一会儿后再观察一下：
[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-54766f574f ??4 ????????4 ????????4 ??????4m24s ??httpd-rollout-test ??httpd:2.4.33 ??pod-template-hash=54766f574f,test=httpddeployment-rollout-5fb9c69c5c ??0 ????????0 ????????0 ??????7m3s ???httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd[root@k8s-m ~]# kubectl get deployment -o wideNAME ????????????????DESIRED ??CURRENT ??UP-TO-DATE ??AVAILABLE ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout ??4 ????????4 ????????4 ???????????4 ??????????7m18s ??httpd-rollout-test ??httpd:2.4.33 ??test=httpd[root@k8s-m ~]# kubectl get pod -o wideNAME ?????????????????????????????????READY ??STATUS ???RESTARTS ??AGE ????IP ????????????NODE ????NOMINATED NODEdeployment-rollout-54766f574f-668pc ??1/1 ????Running ??0 ?????????4m48s ??10.244.1.114 ??k8s-n1 ??<none>deployment-rollout-54766f574f-h7gf9 ??1/1 ????Running ??0 ?????????99s ????10.244.2.50 ???k8s-n2 ??<none>deployment-rollout-54766f574f-ssz67 ??1/1 ????Running ??0 ?????????4m49s ??10.244.2.49 ???k8s-n2 ??<none>deployment-rollout-54766f574f-vklvr ??1/1 ????Running ??0 ?????????41s ????10.244.1.115 ??k8s-n1 ??<none>在此过程中，我们会发现，ReplicaSet deployment-rollout-5fb9c69c5c逐步被deployment-rollout-54766f574f取代，创建新版本的Pod之后，原始版本的Pod被终止。这是一个平滑的升级过程。Kubernetes提供了两个参数maxSurge和maxUnavailable来精细控制Pod的替换数量。
2.3 版本的回滚。
默认情况下，Kubernetes只会保留最近几个revision。在上面的升级过程中，通过revisionHistoryLimit设置了revision的数量。我们通过命令来看一下：
[root@k8s-m ~]# kubectl rollout history deployment deployment-rolloutdeployment.extensions/deployment-rolloutREVISION ?CHANGE-CAUSE1 ????????<none>2 ????????<none>继续升级。新版的YAML如下：
apiVersion: apps/v1beta1kind: Deploymentmetadata: ?name: deployment-rolloutspec: ?revisionHistoryLimit: 10 ?replicas: 4 ?template: ???metadata: ?????labels: ???????test: httpd ???spec: ?????containers: ?????- name: httpd-rollout-test ???????image: httpd:2.4.34 ???????ports: ???????- containerPort: 80执行升级并记录升级日志。
[root@k8s-m ~]# kubectl apply -f Httpd-Deployment-rollout-v2.yaml --recorddeployment.apps/deployment-rollout configured[root@k8s-m ~]# kubectl rollout history deployment deployment-rolloutdeployment.extensions/deployment-rolloutREVISION ?CHANGE-CAUSE1 ????????<none>2 ????????<none>3 ????????kubectl apply --filename=Httpd-Deployment-rollout-v2.yaml --record=true[root@k8s-m ~]# kubectl get deployment deployment-rollout -o wideNAME ????????????????DESIRED ??CURRENT ??UP-TO-DATE ??AVAILABLE ??AGE ??CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout ??4 ????????4 ????????4 ???????????4 ??????????31m ??httpd-rollout-test ??httpd:2.4.34 ??test=httpd[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-54766f574f ??0 ????????0 ????????0 ??????29m ????httpd-rollout-test ??httpd:2.4.33 ??pod-template-hash=54766f574f,test=httpddeployment-rollout-54fc66bb6 ???4 ????????4 ????????4 ??????6m12s ??httpd-rollout-test ??httpd:2.4.34 ??pod-template-hash=54fc66bb6,test=httpddeployment-rollout-5fb9c69c5c ??0 ????????0 ????????0 ??????32m ????httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd[root@k8s-m ~]# kubectl get pod -o wideNAME ????????????????????????????????READY ??STATUS ???RESTARTS ??AGE ????IP ????????????NODE ????NOMINATED NODEdeployment-rollout-54fc66bb6-2zvhk ??1/1 ????Running ??0 ?????????6m26s ??10.244.1.116 ??k8s-n1 ??<none>deployment-rollout-54fc66bb6-7rsj6 ??1/1 ????Running ??0 ?????????4m16s ??10.244.1.117 ??k8s-n1 ??<none>deployment-rollout-54fc66bb6-nlx4h ??1/1 ????Running ??0 ?????????6m26s ??10.244.2.51 ???k8s-n2 ??<none>deployment-rollout-54fc66bb6-xxnrg ??1/1 ????Running ??0 ?????????6m24s ??10.244.2.52 ???k8s-n2 ??<none>修改YAML文件中镜像的版本继续升级，观察升级结果：
[root@k8s-m ~]# kubectl rollout history deployment deployment-rolloutdeployment.extensions/deployment-rolloutREVISION ?CHANGE-CAUSE1 ????????<none>2 ????????<none>3 ????????kubectl apply --filename=Httpd-Deployment-rollout-v2.yaml --record=true4 ????????kubectl apply --filename=Httpd-Deployment-rollout-v3.yaml --record=true[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-54766f574f ??0 ????????0 ????????0 ??????33m ????httpd-rollout-test ??httpd:2.4.33 ??pod-template-hash=54766f574f,test=httpddeployment-rollout-54fc66bb6 ???0 ????????0 ????????0 ??????10m ????httpd-rollout-test ??httpd:2.4.34 ??pod-template-hash=54fc66bb6,test=httpddeployment-rollout-5b99bbfbbc ??4 ????????4 ????????4 ??????2m33s ??httpd-rollout-test ??httpd:2.4.35 ??pod-template-hash=5b99bbfbbc,test=httpddeployment-rollout-5fb9c69c5c ??0 ????????0 ????????0 ??????36m ????httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd[root@k8s-m ~]# kubectl get pod -o wideNAME ?????????????????????????????????READY ??STATUS ???RESTARTS ??AGE ????IP ????????????NODE ????NOMINATED NODEdeployment-rollout-5b99bbfbbc-7mdg9 ??1/1 ????Running ??0 ?????????65s ????10.244.1.119 ??k8s-n1 ??<none>deployment-rollout-5b99bbfbbc-9mfbk ??1/1 ????Running ??0 ?????????2m40s ??10.244.1.118 ??k8s-n1 ??<none>deployment-rollout-5b99bbfbbc-jn5sb ??1/1 ????Running ??0 ?????????2m40s ??10.244.2.53 ???k8s-n2 ??<none>deployment-rollout-5b99bbfbbc-tr6t2 ??1/1 ????Running ??0 ?????????2m38s ??10.244.2.54 ???k8s-n2 ??<none>httpd的image均已经升级到2.4.35，接下来我们试一下回滚到v2版本：
[root@k8s-m ~]# kubectl rollout undo deployment deployment-rollout --to-revision=3deployment.extensions/deployment-rollout[root@k8s-m ~]# kubectl get deployment -o wideNAME ????????????????DESIRED ??CURRENT ??UP-TO-DATE ??AVAILABLE ??AGE ??CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout ??4 ????????4 ????????4 ???????????4 ??????????42m ??httpd-rollout-test ??httpd:2.4.34 ??test=httpd[root@k8s-m ~]# kubectl get replicaset -o wideNAME ???????????????????????????DESIRED ??CURRENT ??READY ??AGE ????CONTAINERS ??????????IMAGES ????????SELECTORdeployment-rollout-54766f574f ??0 ????????0 ????????0 ??????39m ????httpd-rollout-test ??httpd:2.4.33 ??pod-template-hash=54766f574f,test=httpddeployment-rollout-54fc66bb6 ???4 ????????4 ????????4 ??????16m ????httpd-rollout-test ??httpd:2.4.34 ??pod-template-hash=54fc66bb6,test=httpddeployment-rollout-5b99bbfbbc ??0 ????????0 ????????0 ??????8m35s ??httpd-rollout-test ??httpd:2.4.35 ??pod-template-hash=5b99bbfbbc,test=httpddeployment-rollout-5fb9c69c5c ??0 ????????0 ????????0 ??????42m ????httpd-rollout-test ??httpd:2.2.31 ??pod-template-hash=5fb9c69c5c,test=httpd[root@k8s-m ~]# kubectl get pod -o wideNAME ????????????????????????????????READY ??STATUS ???RESTARTS ??AGE ??IP ????????????NODE ????NOMINATED NODEdeployment-rollout-54fc66bb6-bjskn ??1/1 ????Running ??0 ?????????68s ??10.244.1.121 ??k8s-n1 ??<none>deployment-rollout-54fc66bb6-c65th ??1/1 ????Running ??0 ?????????70s ??10.244.2.55 ???k8s-n2 ??<none>deployment-rollout-54fc66bb6-cwpbk ??1/1 ????Running ??0 ?????????70s ??10.244.1.120 ??k8s-n1 ??<none>deployment-rollout-54fc66bb6-lz9xt ??1/1 ????Running ??0 ?????????68s ??10.244.2.56 ???k8s-n2 ??<none>[root@k8s-m ~]# kubectl rollout history deployment deployment-rolloutdeployment.extensions/deployment-rolloutREVISION ?CHANGE-CAUSE1 ????????<none>2 ????????<none>4 ????????kubectl apply --filename=Httpd-Deployment-rollout-v3.yaml --record=true5 ????????kubectl apply --filename=Httpd-Deployment-rollout-v2.yaml --record=true每次升级或回滚操作之后REVISION的数字都会增加1。通过kubectl history，我们可以看到每次升级记录，--record记录了每次操作的详细过程。通过kubectl undo执行回滚操作，选项--to-revision指定了回滚的修订版本号。
三.总结
3.1. 再次被Kubernetes的魅力所折服，平常工作中的灰度升级/发布/更新（按批次停止老版本实例，启用新版本实例，新老版本共存，逐步扩大新版本范围，最终把所有用户迁移到新版本上），蓝绿升级/发布/更新（不停止老版本，另外部署一套新版本，新版本通过测试发布后删除老版本），滚动升级/发布/更新（一个或多个服务停止，执行更新，逐步将新版本投入使用，周而复始，最终完成整个集群中所有实例的版本更新）这些概念理解更加透彻。
3.2. 目前有些资料已经不适用于新版本了，不要被网上的资料所误导，一定要立足与官方文档和系统帮助。例如：
Kubernetes 的Deploy相关的命令只有:
Deploy Commands: ?rollout ???????Manage the rollout of a resource ?scale ?????????为 Deployment, ReplicaSet, Replication Controller 或者 Job 设置一个新的副本数量 ?autoscale ?????自动调整一个 Deployment, ReplicaSet, 或者 ReplicationController 的副本数量Rollout可用资源类型：
Valid resource types include: ?* deployments ?* daemonsets ?* statefulsets3.3 Rollout updat也可以通过YAML来实现，后续文章会介绍。
四.相关资料
4.1 本文相关的yaml文件
4.2 官方资料
Kubernetes的Rolling Update实战
原文地址：http://blog.51cto.com/3842834/2314151