Kubernetes 初始化容器顺序启动

最近工作中需要保证容器启动之前PostgreSQL先启动，然后Apollo再启动，不然会出现配置加载错误的问题。Kubernetes的初始化容器就能够满足这种场景。

InitContainers能够按照资源文件中初始化容器的顺序依次启动

apiVersion: apps/v1
kind: Deployment
metadata:
  name: openailab-discovery-service
  namespace: oas-uat
  labels:
    name: openailab-discovery-service
spec:
  replicas: 1
  selector:
    matchLabels:
      name: openailab-discovery-service
  template:
    metadata:
      labels:
        name: openailab-discovery-service
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: env
                operator: In
                values:
                - dev
      containers:
      - name: openailab-discovery-service
        image: 192.168.3.202:8088/oascloud/openailab-discovery-service:latest
        env:
        - name: APOLLO_APP_ID
          value: 'openailab-discovery-service'
        - name: APOLLO_EUREKA_URI
          value: 'http://10.98.100.95:8082/'
        - name: APOLLO_NAMESPACE
          value: 'application'
        volumeMounts:
        - name: openailab-discovery-service
          mountPath: /usr/local/logs
        command: ['sh','-c','java -server -Xms512m -Xmx1024m -Djava.io.tmpdir=/var/tmp -Duser.timezone=Asia/Shanghai -jar openailab-discovery-service-*.jar --server.port=8080 --spring.profiles.active=remote']
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: 512Mi
            cpu: 250m
          limits:
            memory: 1024Mi
            cpu: 500m
      initContainers:
      - name: init-postgresql
        image: busybox
        command: ['sh', '-c']
        args:
        - echo Prepare to postgresql initialize..;
          until nc -w 1 -z 10.98.70.86 5432;
          do echo Waiting for postgresql initialization to complete..; sleep 10; done;
          echo Postgresql Initialization successful!;
      - name: init-apollo
        image: busybox
        command: ['sh', '-c']
        args:
        - echo Prepare to apollo initialize..;
          until nc -w 1 -z 10.98.100.95 8081;
          do echo Waiting for eureka initialization to complete..; sleep 10; done;
          echo Eureka is ready.;
          until nc -w 1 -z 10.98.100.95 8091;
          do echo Waiting for admin initialization to complete..; sleep 10; done;
          echo Admin is ready.;
          echo Apollo Initialization successful!;
      volumes:
      - name: openailab-discovery-service
        hostPath:
          path: /usr/local/logs

其中10.98.70.86是PostgreSQL容器集群IP（clusterIP），5432是PostgreSQL端口，10.98.100.95是Apollo的容器集群IP，8081、8091分别是Apollo的Eureka、Admin端口，以上配置方式就能够保证在PostgreSQL完全起来之后，再启动Apollo，待两个初始化容器都启动完成之后，最后启动我们的 openailab-discovery-service 容器就可以了。