Spring Cloud Gateway Kubernetes Eureka java.net.UnknownHostException：解析失败

Posted 2023-02-26

【中文标题】Spring Cloud Gateway Kubernetes Eureka java.net.UnknownHostException：解析失败

【英文标题】：Spring Cloud Gateway Kubernetes Eureka java.net.UnknownHostException: failed to resolve

【发布时间】：2021-12-09 19:32:08

【问题描述】：

我正在开发一个具有微服务架构的项目。我有 Spring 云网关、eureka 服务发现和预订微服务。当我在本地运行这些应用程序时，一切正常。当我用 docker compose 运行这些仍然没有问题。但是当我将这些部署到 kubernetes 时，我在 api 网关上遇到错误。当我向 API 网关上的 /book 发送 get 请求时出现此错误

api 网关错误：

java.net.UnknownHostException: failed to resolve 'book-service-55665db7ff-bd75t' after 2 queries 
        at io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1046) ~[netty-resolver-dns-4.1.68.Final.jar!/:4.1.68.Final]
        Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
        |_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
        |_ checkpoint ⇢ HTTP GET "/book" [ExceptionHandlingWebHandler]

api网关配置：

server:
  port: 8084
spring:
  application:
    name: api-gateway
  cloud:
    gateway:
      routes:
      - id: book
        uri: lb://BOOK-SERVICE/book
        predicates:
        - Path=/book/**
      - id: author
        uri: lb://BOOK-SERVICE/author
        predicates:
        - Path=/author/**
      - id: genre
        uri: lb://BOOK-SERVICE/genre
        predicates:
        - Path=/genre/**

预订微服务配置：

spring:
  application:
    name: BOOK-SERVICE
  datasource:
    url: jdbc:postgresql://localhost:5432/book_service
    username: postgres
    password: password
  jpa:
    hibernate:
      ddl-auto: update
    properties:
      hibernate:
        dialect: org.hibernate.dialect.PostgreSQL10Dialect
server:
  port: 8081

kubernetes 清单：

#secret
apiVersion: v1
kind: Secret
metadata:
  name: database
type: Opaque
data:
  password: cGFzc3dvcmQ=
---
#api gateway
apiVersion: apps/v1
kind: Deployment
metadata:
  name: api-gateway
  labels:
    app: api-gateway
spec:
  replicas: 1
  selector:
    matchLabels:
      app: api-gateway
  template:
    metadata:
      labels:
        app: api-gateway
    spec:
      containers:
      - name: api-gateway
        image: rikaciv802/api-gateway
        ports:
        - containerPort: 8084
        env:
        - name: eureka.client.serviceUrl.defaultZone
          value: http://service-discovery:8761/eureka
---
apiVersion: v1
kind: Service
metadata:
  name: api-gateway
spec:
  selector:
    app: api-gateway
  type: LoadBalancer
  ports:
    - protocol: TCP
      port: 8084
      targetPort: 8084
      nodePort: 30000
---
#service discovery
apiVersion: apps/v1
kind: Deployment
metadata:
  name: service-discovery
  labels:
    app: service-discovery
spec:
  replicas: 1
  selector:
    matchLabels:
      app: service-discovery
  template:
    metadata:
      labels:
        app: service-discovery
    spec:
      containers:
      - name: service-discovery
        image: rikaciv802/service-discovery
        ports:
        - containerPort: 8761
---
apiVersion: v1
kind: Service
metadata:
  name: service-discovery
spec:
  selector:
    app: service-discovery
  ports:
    - protocol: TCP
      port: 8761
      targetPort: 8761
---
#book service
apiVersion: apps/v1
kind: Deployment
metadata:
  name: book-service-database
  labels:
    app: book-service-database
spec:
  replicas: 1
  selector:
    matchLabels:
      app: book-service-database
  template:
    metadata:
      labels:
        app: book-service-database
    spec:
      containers:
      - name: book-service-database
        image: postgres:14.0
        ports:
        - containerPort: 5432
        env:
        - name: POSTGRES_DB
          value: book_service
        - name: POSTGRES_PASSWORD
          valueFrom:
            secretKeyRef:
              name: database
              key: password
---
apiVersion: v1
kind: Service
metadata:
  name: book-service-database
spec:
  selector:
    app: book-service-database
  ports:
    - protocol: TCP
      port: 5432
      targetPort: 5432
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: book-service
  labels:
    app: book-service
spec:
  replicas: 1
  selector:
    matchLabels:
      app: book-service
  template:
    metadata:
      labels:
        app: book-service
    spec:
      containers:
      - name: book-service
        image: rikaciv802/book-service
        ports:
        - containerPort: 8081
        env:
        - name: eureka.client.serviceUrl.defaultZone
          value: http://service-discovery:8761/eureka
        - name: SPRING_DATASOURCE_URL
          value: jdbc:postgresql://book-service-database:5432/book_service
        - name: SPRING_DATASOURCE_PASSWORD
          valueFrom:
            secretKeyRef:
              name: database
              key: password
---
apiVersion: v1
kind: Service
metadata:
  name: book-service
spec:
  selector:
    app: book-service
  ports:
    - protocol: TCP
      port: 8081
      targetPort: 8081

服务发现配置：

eureka:
  client:
    register-with-eureka: false
    fetch-registry: false
server:
  port: 8761

【参考方案1】：

您的 pod 主机名似乎存在 DNS 问题。在 kubernetes 中，pod 的 DNS 名称通常格式如下：pod-ip-address.deployment-name.my-namespace.svc.cluster-domain.example（参见https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#pods）

您可以使用 IP 地址解决此问题：将 eureka.instance.preferIpAddress 设置为 true。

见https://cloud.spring.io/spring-cloud-netflix/multi/multi_spring-cloud-eureka-server.html#spring-cloud-eureka-server-prefer-ip-address

【讨论】：

我需要在服务发现或 eureka 客户端中设置吗？

在尤里卡客户端上。所以他们提供他们的 IP 而不是主机名