Rolling Updates and Rollbacks#

• Rolling Updates
  • 逐个替换Pod，确保应用的高可用性
  • 通过Deployment对象实现

# deployment spec
spec:
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate

Commands:

• Update: kubectl set image deployment/my-deployment my-container=my-image:tag 更新镜像,会更新Deployment的spec.template.spec.containers.image字段, kubectl edit deployment/my-deployment, 应用新deployment kubectl apply -f deployment.yaml
• Update Status: kubectl rollout status deployment/my-deployment
• 查看更新历史: kubectl rollout history deployment/my-deployment
• 回滚: kubectl rollout undo deployment/my-deployment [--to-revision=1 指定回滚版本]

Configure Applications#

Commands Arguments and Environment Variables#

1. image中不存在ENTRYPOINT时，command和args字段会覆盖Dockerfile中的CMD字段

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: my-container
    image: nginx
    command: ["nginx", "-g", "daemon off;"]

2. image中存在ENTRYPOINT时，command和args字段会追加到ENTRYPOINT后

FROM nginx
ENTRYPOINT ["nginx", "-g", "daemon off;"]
CMD ["-g", "worker_processes auto;"]

apiVersion: v1
kind: Pod
metadata:
  name: my-nginx
spec:
  containers:
  - name: nginx
    image: my-nginx-image
    # 覆盖 ENTRYPOINT
    command: ["nginx", "-g", "daemon off; worker_processes 8;"] # Dockerfile Entrypoint
    # 覆盖 CMD
    args: ["-g", "worker_processes 16;"]

3. Environment Variables

# sepc
spec:
  containers:
  - name: my-container
    image: my-image
    env: # 环境变量
    - name: MY_ENV # plain text
      value: my-value
    - name: MY_ENV_FROM_SECRET # 从secret中获取
      valueFrom:
        secretKeyRef:
          name: my-secret
          key: my-key

# 加载全部secret中的环境变量
---
apiVersion: v1 
kind: Pod 
metadata:
  labels:
    name: webapp-pod
  name: webapp-pod
  namespace: default 
spec:
  containers:
  - image: kodekloud/simple-webapp-mysql
    imagePullPolicy: Always
    name: webapp
    envFrom:
    - secretRef:
        name: db-secret