Kubernetes的Rolling Update實戰

發布時間：2020-07-24 10:06:01 來源：網絡閱讀：659 作者：耕耘實錄欄目：云計算

一.背景

隨著Kubernetes的進一步深入使用，我們越來越體會到它給我們的工作帶來的高效與便利。Rolling Update是Kubernetes系統中的一個強大的功能，能夠為我們的運維工作帶來極大的便利。

二.步驟

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

執行命令：

[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 將初始版本升級。

升級到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

執行命令：

[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>

一會兒后再觀察一下：

[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>

在此過程中，我們會發現，ReplicaSet deployment-rollout-5fb9c69c5c逐步被deployment-rollout-54766f574f取代，創建新版本的Pod之后，原始版本的Pod被終止。這是一個平滑的升級過程。Kubernetes提供了兩個參數maxSurge和maxUnavailable來精細控制Pod的替換數量。

2.3 版本的回滾。

默認情況下，Kubernetes只會保留最近幾個revision。在上面的升級過程中，通過revisionHistoryLimit設置了revision的數量。我們通過命令來看一下：

[root@k8s-m ~]# kubectl rollout history deployment deployment-rollout
deployment.extensions/deployment-rollout
REVISION  CHANGE-CAUSE
1         <none>
2         <none>

繼續升級。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

執行升級并記錄升級日志。

[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文件中鏡像的版本繼續升級，觀察升級結果：

[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均已經升級到2.4.35，接下來我們試一下回滾到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

每次升級或回滾操作之后REVISION的數字都會增加1。通過kubectl history，我們可以看到每次升級記錄，--record記錄了每次操作的詳細過程。通過kubectl undo執行回滾操作，選項--to-revision指定了回滾的修訂版本號。

三.總結

3.1. 再次被Kubernetes的魅力所折服，平常工作中的灰度升級/發布/更新（按批次停止老版本實例，啟用新版本實例，新老版本共存，逐步擴大新版本范圍，最終把所有用戶遷移到新版本上），藍綠升級/發布/更新（不停止老版本，另外部署一套新版本，新版本通過測試發布后刪除老版本），滾動升級/發布/更新（一個或多個服務停止，執行更新，逐步將新版本投入使用，周而復始，最終完成整個集群中所有實例的版本更新）這些概念理解更加透徹。

3.2. 目前有些資料已經不適用于新版本了，不要被網上的資料所誤導，一定要立足與官方文檔和系統幫助。例如：

Kubernetes 的Deploy相關的命令只有:

Deploy Commands:
  rollout        Manage the rollout of a resource
  scale          為 Deployment, ReplicaSet, Replication Controller 或者 Job 設置一個新的副本數量
  autoscale      自動調整一個 Deployment, ReplicaSet, 或者 ReplicationController 的副本數量

Rollout可用資源類型：

Valid resource types include:
  * deployments
  * daemonsets
  * statefulsets

3.3 Rollout updat也可以通過YAML來實現，后續文章會介紹。

四.相關資料

4.1 本文相關的yaml文件

4.2 官方資料

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Kubernetes的Rolling Update實戰

一.背景

二.步驟

2.1 部署最初始版本Deployment。

2.2 將初始版本升級。

2.3 版本的回滾。

三.總結

四.相關資料

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Kubernetes的Rolling Update實戰

一.背景

二.步驟

2.1 部署最初始版本Deployment。

2.2 將初始版本升級。

2.3 版本的回滾。

三.總結

四.相關資料

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