今天進入到 Deployment 他是一個控制 pod & replicaset 的設定方式，前一篇有講到，基本上都是不建議單獨使用 pod 來做部署的動作，接下來我們來看看吧。

Deploymenet

首先，不囉唆直接先來一個標準的 Deployment範例，把下面的文字存成 nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3 # 同時建立 3 個 nginx 的 pod
  # replicaset 的效果套用在帶有 app=nginx 的 pod 上
  # 必須要與下面的 pod label 有相符合
  selector:
    matchLabels:
      app: nginx
  # .spec.template 其實就是 pod 的定義
  template:
    # pod metadata
    metadata:
      # 設定給 pod 的 label 資訊
      labels:
        app: nginx
    spec:
      # 這邊可以看到，其實跟昨天的 nginx 是一樣的。
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

接著下 kubectl --kubeconfig ~/.kube/k3s.yaml apply -f nginx-deployment.yaml

接著做檢查看看 kubectl --kubeconfig ~/.kube/k3s.yaml get pods 就會看到下面回應

NAME                               READY   STATUS    RESTARTS   AGE
nginx-deployment-d46f5678b-ghjsx   1/1     Running   0          50s
nginx-deployment-d46f5678b-zxprl   1/1     Running   0          50s
nginx-deployment-d46f5678b-zwrdk   1/1     Running   0          50s

也可以下 kubectl --kubeconfig ~/.kube/k3s.yaml get deployment

#READY  就緒幾個/總共幾個
#UP-TO-DATE 有幾個 pod 副本已經 onboard
#AVAILABLE 目前有多少pod 副本可以運作
#Age pod運行時間

NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           115s

Scale

我們來嘗試看看，怎麼透過 Deployment 去做 scale

# 設定要擴增10個
$ kubectl --kubeconfig ~/.kube/k3s.yaml scale deployment/nginx-deployment --replicas=10
deployment.apps/nginx-deployment scaled


# 檢查pod 數量

$ kubectl --kubeconfig ~/.kube/k3s.yaml get pods
NAME                               READY   STATUS    RESTARTS   AGE
nginx-deployment-d46f5678b-ghjsx   1/1     Running   0          8m51s
nginx-deployment-d46f5678b-zxprl   1/1     Running   0          8m51s
nginx-deployment-d46f5678b-zwrdk   1/1     Running   0          8m51s
nginx-deployment-d46f5678b-qwrgt   1/1     Running   0          53s
nginx-deployment-d46f5678b-n84gc   1/1     Running   0          53s
nginx-deployment-d46f5678b-5w8jg   1/1     Running   0          53s
nginx-deployment-d46f5678b-2rv8x   1/1     Running   0          53s
nginx-deployment-d46f5678b-9ljzr   1/1     Running   0          53s
nginx-deployment-d46f5678b-kdvlg   1/1     Running   0          53s
nginx-deployment-d46f5678b-88xpz   1/1     Running   0          53s

Deployment revision

# 更新一個不存在的版本
$ kubectl --kubeconfig ~/.kube/k3s.yaml set image deployment/nginx-deployment nginx=nginx1.9.2
deployment.extensions/nginx-deployment image updated

# 因為版本不存在，所以會卡住，需要強制中斷
$ kubectl rollout status deployments nginx-deployment
Waiting for deployment "nginx-deployment" rollout to finish: 5 out of 10 new replicas have been updated...
^C

# 可以下這句就可以回復上一個動作。 接下來再重新執行上一句就可以看到正常的狀態。
$ kubectl --kubeconfig ~/.kube/k3s.yaml rollout undo deployment/nginx-deployment
deployment.apps/nginx-deployment rolled back

透過以上介紹，我們知道了一些基礎 Deployment 的教學。明天我們來介紹一些實務上 Deployment 的特別設定。