Kubernetes 部署在使用单个副本时不执行滚动更新

Question

我修改了部署配置 (production.yaml)，更改了容器映像值。

然后我运行这个：kubectl replace -f production.yaml.

发生这种情况时，我的服务似乎没有响应，此外：

kubectl get pods:

wordpress-2105335096-dkrvg 3/3 Running 0 47s

稍后...:[=17=]

wordpress-2992233824-l4287 3/3 Running 0 14s

稍后...:[=17=]

wordpress-2992233824-l4287 0/3 ContainerCreating 0 7s

它似乎在新 pod 出现之前终止了前一个 pod Running... 为什么？

produciton.yaml:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  replicas: 1
  selector:
    matchLabels:
      app: wordpress
  template:
    metadata:
      labels:
        app: wordpress
    spec:
      terminationGracePeriodSeconds: 30
      containers:
        - image: eu.gcr.io/abcxyz/wordpress:deploy-1502463532
          name: wordpress
          imagePullPolicy: "Always"
          env:
            - name: WORDPRESS_HOST
              value: localhost
            - name: WORDPRESS_DB_USERNAME
              valueFrom:
                secretKeyRef:
                  name: cloudsql-db-credentials
                  key: username
          volumeMounts:
            - name: wordpress-persistent-storage
              mountPath: /var/www/html
        - image: eu.gcr.io/abcxyz/nginx:deploy-1502463532
          name: nginx
          imagePullPolicy: "Always"
          ports:
            - containerPort: 80
              name: nginx
          volumeMounts:
            - name: wordpress-persistent-storage
              mountPath: /var/www/html
        - image: gcr.io/cloudsql-docker/gce-proxy:1.09
          name: cloudsql-proxy
          command: ["/cloud_sql_proxy", "--dir=/cloudsql",
                    "-instances=abcxyz:europe-west1:wordpressdb2=tcp:3306",
                    "-credential_file=/secrets/cloudsql/credentials.json"]
          volumeMounts:
            - name: cloudsql-instance-credentials
              mountPath: /secrets/cloudsql
              readOnly: true
            - name: ssl-certs
              mountPath: /etc/ssl/certs
            - name: cloudsql
              mountPath: /cloudsql
      volumes:
        - name: wordpress-persistent-storage
          gcePersistentDisk:
            pdName: wordpress-disk
            fsType: ext4

        - name: cloudsql-instance-credentials
          secret:
            secretName: cloudsql-instance-credentials
        - name: ssl-certs
          hostPath:
            path: /etc/ssl/certs
        - name: cloudsql
          emptyDir:

Answer 1

根据 Kubernetes 文档，我认为此行为是正确的。假设您为部署指定 n 个副本，则 Kubernetes 在更新部署时将执行以下步骤：

终止旧 pods，同时确保至少 n - 1 总数 pods 启动
创建新的 pods 直到最多 n + 1 总数 pods 可用
一旦新 pods 上线，返回第 1 步，直到 n 个新 pods 上线

在你的情况下 n = 1，这意味着在第一步中，所有旧的 pods 将被终止。

有关详细信息，请参阅 Updating a Deployment：

Deployment can ensure that only a certain number of Pods may be down while they are being updated. By default, it ensures that at least 1 less than the desired number of Pods are up (1 max unavailable). Deployment can also ensure that only a certain number of Pods may be created above the desired number of Pods. By default, it ensures that at most 1 more than the desired number of Pods are up (1 max surge). In a future version of Kubernetes, the defaults will change from 1-1 to 25%-25%.

Kubernetes 部署在使用单个副本时不执行滚动更新

Kubernetes deployment does not perform a rolling update when using a single replica

kubernetes

kubectl