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2023 iThome 鐵人賽
DAY 11
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DevOps

第一次參賽就學 Kubernetes系列 第 11 篇

[Day 11] Deployment (下篇)

15th鐵人賽 deployment
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接續前篇的內容：

  1. 進行 upgrade
  2. 進行 rollback
  3. 刪除 deployment

底下為前一篇的 nginx-deploy.yaml。

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
  labels:
    app: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: nginx
        image: nginx:1.20.0
        ports:
        - containerPort: 80

2. 進行 upgrade

目的：將該應用程式的 container image 由 nginx:1.20.0 更新為 nginx:1.23.0。

開始前我先以 kubectl create -f nginx-deploy.yaml 來建立 deployment。先來看 2 個實用的指令：

  1. kubectl rollout status
  2. kubectl rollout history

第 1 個可以用來查看 rollout 狀態。

kubectl rollout status deployment/nginx-deploy

第 2 個可以查看 rollout 的 revision 與歷史紀錄。

kubectl rollout history deployment/nginx-deploy

待會使用以上 2 種指令來觀察 rollout 變化。

  1. 將 image 由 nginx:1.20.0 修改成 nginx:1.23.0，加上 --record 會在 rollout history 裡紀錄該指令。

    • 可以使用 kubectl edit。

      kubectl edit deployment nginx-deploy --record

deployment.apps/nginx-deploy edited

    • 或是使用 kubectl set image。

      kubectl set image deployment nginx-deploy nginx=nginx:1.23.0 --record

deployment.apps/nginx-deploy image updated

  2. 因目前的更新政策是 RollingUpdate，可以查看到 deployment 建立新的 nginx:1.23.0 pods，依序關閉舊的 nginx:1.20.0 pods，在此政策下版本更新並不會中斷應用程式的存取。

    kubectl rollout status deployment/nginx-deploy

Waiting for deployment "nginx-deploy" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "nginx-deploy" rollout to finish: 1 old replicas are pending termination...
deployment "nginx-deploy" successfully rolled out

  3. 可以從 kubectl describe 裡查看 deployment 的 Events。

    kubectl describe deploy nginx-deploy

Name:                   nginx-deploy
Namespace:              default
CreationTimestamp:      Tue, 26 Sep 2023 15:34:28 +0800
Labels:                 app=my-app
Annotations:            deployment.kubernetes.io/revision: 2
                        kubernetes.io/change-cause: kubectl edit deployment nginx-deploy --record=true
Selector:               app=my-app
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=my-app
  Containers:
   nginx:
    Image:        nginx:1.23.0
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deploy-69d4d4678b (3/3 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  2m19s  deployment-controller  Scaled up replica set nginx-deploy-65b6d5d9d9 to 3
  Normal  ScalingReplicaSet  49s    deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 1
  Normal  ScalingReplicaSet  48s    deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 2 from 3
  Normal  ScalingReplicaSet  48s    deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 2 from 1
  Normal  ScalingReplicaSet  47s    deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 1 from 2
  Normal  ScalingReplicaSet  47s    deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 3 from 2
  Normal  ScalingReplicaSet  46s    deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 0 from 1

  4. 另外可以從 kubectl rollout history 看到建立的 revision 是因為哪個指令產生的 (CHANGE-CAUSE)。第一行是一開始使用 kubectl create 建立 deployment 的指令，第二行是剛才輸入 kubectl edit 修改 image 的指令。

    kubectl rollout history deployment/nginx-deploy

deployment.apps/nginx-deploy
REVISION  CHANGE-CAUSE
1         kubectl create --filename=nginx-deploy.yaml --record=true
2         kubectl edit deployment nginx-deploy --record=true

  5. 查看 pods 是否 ready。

    kubectl get po

NAME                            READY   STATUS    RESTARTS   AGE
nginx-deploy-69d4d4678b-dj24t   1/1     Running   0          101s
nginx-deploy-69d4d4678b-tcbkn   1/1     Running   0          100s
nginx-deploy-69d4d4678b-z4gpb   1/1     Running   0          99s

3. 進行 rollback

目的：復原至應用程式的前一版，也就是將 image 由 nginx:1.23.0 回滾至 nginx:1.20.0。

  1. 使用 kubectl rollout undo。

    kubectl rollout undo deployment/nginx-deploy

deployment.apps/nginx-deploy rolled back

  2. 觀察 k8s 正依序建立 nginx:1.20.0 新的 pods，並逐步關閉 nginx:1.23.0 舊的 pods，回復至 revision 1。

    kubectl rollout status deployment/nginx-deploy

Waiting for deployment "nginx-deploy" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deploy" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deploy" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deploy" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "nginx-deploy" rollout to finish: 1 old replicas are pending termination...
deployment "nginx-deploy" successfully rolled out

  3. 查看是否真的復原、其 image 應為 nginx:1.20.0。

    kubectl describe deploy nginx-deploy

Name:                   nginx-deploy
Namespace:              default
CreationTimestamp:      Tue, 26 Sep 2023 15:34:28 +0800
Labels:                 app=my-app
Annotations:            deployment.kubernetes.io/revision: 3
                        kubernetes.io/change-cause: kubectl create --filename=nginx-deploy.yaml --record=true
Selector:               app=my-app
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=my-app
  Containers:
   nginx:
    Image:        nginx:1.20.0
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deploy-65b6d5d9d9 (3/3 replicas created)
Events:
  Type    Reason             Age                From                   Message
  ----    ------             ----               ----                   -------
  Normal  ScalingReplicaSet  7m56s              deployment-controller  Scaled up replica set nginx-deploy-65b6d5d9d9 to 3
  Normal  ScalingReplicaSet  6m26s              deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 1
  Normal  ScalingReplicaSet  6m25s              deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 2 from 3
  Normal  ScalingReplicaSet  6m25s              deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 2 from 1
  Normal  ScalingReplicaSet  6m24s              deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 1 from 2
  Normal  ScalingReplicaSet  6m24s              deployment-controller  Scaled up replica set nginx-deploy-69d4d4678b to 3 from 2
  Normal  ScalingReplicaSet  6m23s              deployment-controller  Scaled down replica set nginx-deploy-65b6d5d9d9 to 0 from 1
  Normal  ScalingReplicaSet  31s                deployment-controller  Scaled up replica set nginx-deploy-65b6d5d9d9 to 1 from 0
  Normal  ScalingReplicaSet  30s                deployment-controller  Scaled down replica set nginx-deploy-69d4d4678b to 2 from 3
  Normal  ScalingReplicaSet  27s (x4 over 30s)  deployment-controller  (combined from similar events): Scaled down replica set nginx-deploy-69d4d4678b to 0 from 1

  4. 再執行以下指令。

    kubectl rollout history deployment/nginx-deploy

deployment.apps/nginx-deploy
REVISION  CHANGE-CAUSE
2         kubectl edit deployment nginx-deploy --record=true
3         kubectl create --filename=nginx-deploy.yaml --record=true

    可以看見 revision 3，但 revision 1 不見了。

    事實上當前的 revision 3 的內容就是 revision 1，意思是退回的 revision 1 被變更成最新的 revision 並將其名子更改為 revision 3。

4. 刪除 deployment

  1. 執行以下指令刪除 deployment。

    kubectl delete deploy nginx-deploy

deployment.apps "nginx-deploy" deleted

  2. 查看 deployment、replicaset 及 pod。

    kubectl get deploy

No resources found in default namespace.

    kubectl get rs,po

No resources found in default namespace.

參考來源

  1. Kubernetes: Getting Started
  2. Kubernetes for the Absolute Beginners - Hands-on

上一篇
[Day 10] Deployment (上篇)
下一篇
[Day 12] Service
系列文
第一次參賽就學 Kubernetes 共 30 篇
  1. 26
    [Day 26] Authentication - Role Based Access Control (RBAC)
  2. 27
    [Day 27] Namespaces
  3. 28
    [Day 28] 使用 Jenkins 建置 CI/CD Pipeline 專案 (一)
  4. 29
    [Day 29] 使用 Jenkins 建置 CI/CD Pipeline 專案 (二)
  5. 30
    [Day 30] Kubernetes 學習資源 & 反思
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