Issue with Docker Compose depends_on Not Working for Naming Server

I'm experiencing an issue with my Docker Compose setup. My service (currency-exchange) depends on both a MySQL database and a naming server. When I add depends_on with the service_healthy condition for the naming server, the entire application fails to start. However, when I remove the dependency on the naming server, the application starts successfully, but the naming server cannot register the service.

The strange part is that depends_on works perfectly with the MySQL container, but it fails when applied to the naming server.

Here is my docker-compose.yml file:

services:
  currency-exchange:
    image: mmusernmae/microservices-currency-exchange-service:0.0.1-SNAPSHOT
    ports:
      - "8000:8000"
    networks:
      - currency-network
    depends_on:
      my-sql-db:
        condition: service_healthy
      naming-server:
        condition: service_healthy
    environment:
      SPRING_DATASOURCE_URL: jdbc:mysql://my-sql-db:3306/currency_exchange_db?createDatabaseIfNotExist=true&useSSL=false&allowPublicKeyRetrieval=true
      SPRING_DATASOURCE_USERNAME: root
      SPRING_DATASOURCE_PASSWORD: mypass55
      EUREKA_CLIENT_SERVICE_URL_DEFAULT_ZONE: http://naming-server:8761/eureka

  my-sql-db:
    image: mysql/mysql-server:latest
    environment:
      MYSQL_ROOT_PASSWORD: mypass55
      MYSQL_DATABASE: currency_exchange_db
      MYSQL_USER: root
      MYSQL_PASSWORD: mypass55
    healthcheck:
      test: ["CMD-SHELL", "mysqladmin ping -h localhost -u root -pmypass55"]
      timeout: 20s
      retries: 10
    ports:
      - "3306:3306"
    networks:
      - currency-network

  naming-server:
    image: mmusernmae/microservices-naming-server:0.0.1-SNAPSHOT
    ports:
      - "8761:8761"
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8761/"]
      interval: 30s
      timeout: 10s
      retries: 5
    networks:
      - currency-network

networks:
  currency-network:

What I've Tried:

• I used depends_on with condition: service_healthy.
• I also tried condition: service_completed_successfully.

Despite these attempts, the issue persists. Does anyone have insights into why depends_on might not work with the naming server but works with the MySQL container? Any suggestions on how to resolve this?

Final solution:

I found the root causes of the issue, and here’s how I resolved it:

1. Incorrect Health Check Configuration for Naming Server:

   The health check for the naming server was not set up correctly. Specifically, the container did not have the curl command available to perform the health check. To resolve this, I created a custom Dockerfile for the naming server, using a base image that includes curl:

   FROM openjdk:17-jdk-slim
   VOLUME /tmp
   RUN apt-get update && apt-get install -y curl
   COPY target/*.jar app.jar
   ENTRYPOINT ["java","-jar", "app.jar"]
   

   This ensured that the health check could be performed successfully.

2. Eureka Client Service URL Configuration Issue:

   After fixing the health check, the services still could not register with the naming server. I discovered that the problem was related to the configuration of the EUREKA_CLIENT_SERVICE_URL_DEFAULT_ZONE property.

   There is a known issue with camel-casing in Spring Boot, where EUREKA_CLIENT_SERVICE_URL_DEFAULT_ZONE is incorrectly converted to eureka.client.serviceurl.defaultzone instead of eureka.client.serviceUrl.defaultZone.

   To fix this, I updated the environment variable to use the correct format:

   environment:
     eureka.client.serviceUrl.defaultZone: http://naming-server:8761/eureka
   

   This change allowed the services to register correctly with the naming server.

For more details, you can refer to this Stack Overflow thread, which helped me identify the configuration issue.