一. 背景
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/v1beta1
- kind: Deployment
- metadata:
- name: deployment-rollout
- spec:
- 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 wide
- NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout 4 4 4 4 107s httpd-rollout-test httpd:2.2.31 test=httpd
- [root@k8s-m ~]# kubectl get replicaset -o wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-5fb9c69c5c 4 4 4 116s httpd-rollout-test httpd:2.2.31 pod-template-hash=5fb9c69c5c,test=httpd
2.2 将初始版本升级.
升级到 2.4.31,YAML 如下:
- apiVersion: apps/v1beta1
- kind: Deployment
- metadata:
- name: deployment-rollout
- spec:
- 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.YAML
- deployment.apps/deployment-rollout configured
- [root@k8s-m ~]# kubectl get deployment -o wide
- NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout 4 5 2 3 3m57s httpd-rollout-test httpd:2.4.33 test=httpd
- [root@k8s-m ~]# kubectl get replicaset -o wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-54766f574f 2 2 0 93s httpd-rollout-test httpd:2.4.33 pod-template-hash=54766f574f,test=httpd
- deployment-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 wide
- NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
- deployment-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 wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-54766f574f 4 4 4 4m24s httpd-rollout-test httpd:2.4.33 pod-template-hash=54766f574f,test=httpd
- deployment-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 wide
- NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout 4 4 4 4 7m18s httpd-rollout-test httpd:2.4.33 test=httpd
- [root@k8s-m ~]# kubectl get pod -o wide
- NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
- deployment-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-rollout
- deployment.extensions/deployment-rollout
- REVISION CHANGE-CAUSE
- 1 <none>
- 2 <none>
继续升级. 新版的 YAML 如下:
- apiVersion: apps/v1beta1
- kind: Deployment
- metadata:
- name: deployment-rollout
- spec:
- 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 --record
- deployment.apps/deployment-rollout configured
- [root@k8s-m ~]# kubectl rollout history deployment deployment-rollout
- deployment.extensions/deployment-rollout
- REVISION CHANGE-CAUSE
- 1 <none>
- 2 <none>
- 3 kubectl apply --filename=Httpd-Deployment-rollout-v2.YAML --record=true
- [root@k8s-m ~]# kubectl get deployment deployment-rollout -o wide
- NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout 4 4 4 4 31m httpd-rollout-test httpd:2.4.34 test=httpd
- [root@k8s-m ~]# kubectl get replicaset -o wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-54766f574f 0 0 0 29m httpd-rollout-test httpd:2.4.33 pod-template-hash=54766f574f,test=httpd
- deployment-rollout-54fc66bb6 4 4 4 6m12s httpd-rollout-test httpd:2.4.34 pod-template-hash=54fc66bb6,test=httpd
- deployment-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 wide
- NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
- deployment-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-rollout
- deployment.extensions/deployment-rollout
- REVISION CHANGE-CAUSE
- 1 <none>
- 2 <none>
- 3 kubectl apply --filename=Httpd-Deployment-rollout-v2.YAML --record=true
- 4 kubectl apply --filename=Httpd-Deployment-rollout-v3.YAML --record=true
- [root@k8s-m ~]# kubectl get replicaset -o wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-54766f574f 0 0 0 33m httpd-rollout-test httpd:2.4.33 pod-template-hash=54766f574f,test=httpd
- deployment-rollout-54fc66bb6 0 0 0 10m httpd-rollout-test httpd:2.4.34 pod-template-hash=54fc66bb6,test=httpd
- deployment-rollout-5b99bbfbbc 4 4 4 2m33s httpd-rollout-test httpd:2.4.35 pod-template-hash=5b99bbfbbc,test=httpd
- deployment-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 wide
- NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
- deployment-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=3
- deployment.extensions/deployment-rollout
- [root@k8s-m ~]# kubectl get deployment -o wide
- NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout 4 4 4 4 42m httpd-rollout-test httpd:2.4.34 test=httpd
- [root@k8s-m ~]# kubectl get replicaset -o wide
- NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
- deployment-rollout-54766f574f 0 0 0 39m httpd-rollout-test httpd:2.4.33 pod-template-hash=54766f574f,test=httpd
- deployment-rollout-54fc66bb6 4 4 4 16m httpd-rollout-test httpd:2.4.34 pod-template-hash=54fc66bb6,test=httpd
- deployment-rollout-5b99bbfbbc 0 0 0 8m35s httpd-rollout-test httpd:2.4.35 pod-template-hash=5b99bbfbbc,test=httpd
- deployment-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 wide
- NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
- deployment-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-rollout
- deployment.extensions/deployment-rollout
- REVISION CHANGE-CAUSE
- 1 <none>
- 2 <none>
- 4 kubectl apply --filename=Httpd-Deployment-rollout-v3.YAML --record=true
- 5 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
- * statefulsets
3.3 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
来源: http://blog.51cto.com/3842834/2314151