Kubernetes Pod應用的滾動更新(八)
阿新 • • 發佈：2018-12-11
一、環境準備
我們緊接上一節的環境，進行下面的操作，如果不清楚的，可以先檢視上一篇博文。
滾動更新是一次只更新一小部分副本，成功後，再更新更多的副本，最終完成所有副本的更新。滾動更新的最大的好處是零停機，整個更新過程始終有副本在執行，從而保證了業務的連續性。
二、更新
我們檢視一下上一節的配置檔案mytest-deploy.yaml。
apiVersion: extensions/v1beta1 kind: Deployment metadata: name: mytest spec: replicas: 3 template: metadata: labels: run: mytest spec: containers: - name: mytest image: wangzan18/mytest:v1 ports: - containerPort: 80
我們看到設定的映象版本為v1，我們檢視一下建立的ReplicaSet。
[[email protected] ~]# kubectl get rs -o wide NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR mytest-88d46bf99 3 3 3 68m mytest wangzan18/mytest:v1 pod-template-hash=88d46bf99,run=mytest
目前執行的 Pod 由 ReplicaSet mytest-88d46bf99進行控制，我們將配置檔案中的 v1 替換為 v2，再次應用。
[[email protected] ~]# kubectl apply -f mytest-deploy.yaml deployment.extensions/mytest configured [[email protected] ~]# kubectl get pods NAME READY STATUS RESTARTS AGE mytest-56c55b4c6-6gjxc 1/1 Running 0 24s mytest-56c55b4c6-f5trx 1/1 Running 0 18s mytest-56c55b4c6-sh5wd 1/1 Running 0 24s mytest-88d46bf99-48f6n 1/1 Terminating 0 70m mytest-88d46bf99-mv6cf 1/1 Terminating 0 70m mytest-88d46bf99-p9w79 1/1 Terminating 0 70m
[[email protected] ~]# kubectl get deploy -o wide
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
mytest 3/3 3 3 72m mytest wangzan18/mytest:v2 run=mytest
[[email protected] ~]# kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
mytest-56c55b4c6 3 3 3 59s mytest wangzan18/mytest:v2 pod-template-hash=56c55b4c6,run=mytest
mytest-88d46bf99 0 0 0 71m mytest wangzan18/mytest:v1 pod-template-hash=88d46bf99,run=mytest我們可以看到 Deployment 的映象更新為wangzan18/mytest:v2，建立了新的 ReplicaSet mytest-56c55b4c6，並管理了三個新的 Pod。
[[email protected] ~]# kubectl describe deployment mytest
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 4m9s deployment-controller Scaled up replica set mytest-56c55b4c6 to 1
Normal ScalingReplicaSet 4m9s deployment-controller Scaled down replica set mytest-88d46bf99 to 2
Normal ScalingReplicaSet 4m9s deployment-controller Scaled up replica set mytest-56c55b4c6 to 2
Normal ScalingReplicaSet 4m3s deployment-controller Scaled down replica set mytest-88d46bf99 to 1
Normal ScalingReplicaSet 4m3s deployment-controller Scaled up replica set mytest-56c55b4c6 to 3
Normal ScalingReplicaSet 4m3s deployment-controller Scaled down replica set mytest-88d46bf99 to 0每次只更新替換一個 Pod。
三、回滾
kubectl apply 每次更新應用時 Kubernetes 都會記錄下當前的配置，儲存為一個 revision（版次），這樣就可以回滾到某個特定 revision。
預設配置下，Kubernetes 只會保留最近的幾個 revision，可以在 Deployment 配置檔案中通過 revisionHistoryLimit 屬性增加 revision 數量。
通過命令kubectl rollout undo我們可以回滾到上一個版本。
[[email protected] ~]# kubectl rollout undo deploy mytest
deployment.extensions/mytest rolled back[[email protected] ~]# kubectl get rs -o wide
NAME DESIRED CURRENT READY AGE CONTAINERS IMAGES SELECTOR
mytest-56c55b4c6 0 0 0 12m mytest wangzan18/mytest:v2 pod-template-hash=56c55b4c6,run=mytest
mytest-88d46bf99 3 3 3 82m mytest wangzan18/mytest:v1 pod-template-hash=88d46bf99,run=mytest可以看到三個 Pod 重新由映象為wangzan18/mytest:v1的ReplicaSet進行接管。