使用 docker 时，如何在 Eureka 客户端中保持 Eureka 服务器 url 动态？

Question

I am using the fabric8 docker-maven-plugin to build image for my Spring boot microservices.

<groupId>io.fabric8</groupId>
<artifactId>docker-maven-plugin</artifactId>

The problem is that while running the application in docker containers I have to specify the Eureka Server Container name to Eureka Client. But if I run it directly as a "Spring Boot APP" I have to use "Localhost:8761/Eureka". Is there a way to make it work both with/without docker something like given below?

eureka:
  client:
    service-url:
      defaultZone: ${EUREKA_SERVER:http://localhost:8761/eureka}

I am not able to pass the value of "EUREKA_SERVER" from the fabrib8 plugin. I have tried the below code to pass the value but it does not work.

<docker.env.JAVA_OPTS>-DEUREKA_SERVER=http://discovery:8761/eureka</docker.env.JAVA_OPTS>

Answer 1

Spring can pickup Environment Variables. So if you add Environment Variables to the Docker Container that Spring Boot is running in, they will work. This avoids the need to provide a static URL up front.

If you use Docker Compose, it could look like this:

services:
  eureka:
    image: springcloud/eureka
    container_name: eureka
    ports:
      - "8761:8761"
    networks:
      - "discovery"
    environment:
      - EUREKA_INSTANCE_PREFERIPADDRESS=true

  spring:
    build:
      context: .
      dockerfile: ./src/main/docker/Dockerfile
    depends_on:
      - eureka
    container_name: spring
    ports:
     - "8080:8080"
    networks:
     - "discovery"
    environment:
      - EUREKA_SERVICE_URL=http://eureka:8761 // This overrides your Spring Property
      - EUREKA_INSTANCE_PREFER_IP_ADDRESS=true
      - LOGGING_FILE=/tmp/admin.log

Note: Since Environment Variables are not YAML, you need to change the format a bit. https://docs.spring.io/spring-boot/docs/1.5.5.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-relaxed-binding