How to Resolve ERR_NAME_NOT_RESOLVED in Docker-Compose for Java Spring and Angular Applications

How can I troubleshoot and resolve the ERR_NAME_NOT_RESOLVED error in a Docker-Compose configuration for my Java Spring and Angular applications?

The ERR_NAME_NOT_RESOLVED error indicates that your application is unable to resolve the hostname of your services defined in a Docker-Compose file. This can often happen due to misconfigurations in the networking settings or a failure to properly expose and link services. In a typical setup with Java Spring and Angular, resolving this issue involves examining both your Docker-Compose file and the configurations of your services.

version: '3'
services:
  spring:
    image: springapp:latest
    ports:
      - "8080:8080"
    networks:
      - app-network
    depends_on:
      - database

  angular:
    image: angularapp:latest
    ports:
      - "4200:4200"
    networks:
      - app-network

  database:
    image: postgres:latest
    networks:
      - app-network

networks:
  app-network:
    driver: bridge

Causes

• Incorrect service names in the Docker-Compose file.
• Network issues due to Docker's network configurations.
• Misconfigured DNS settings inside your containers.
• Services not starting up in the required sequence.

Solutions

• Ensure that all service names are correctly defined and correspond to their respective services in Docker-Compose.
• Check your Docker network configuration. Use `docker network ls` and `docker network inspect <network_name>` to review the network settings.
• Verify that you are exposing the correct ports in your Docker-Compose file. Make sure to map the application ports correctly to host ports.
• Use `depends_on` in your Docker-Compose file to control the startup order of services. This can help ensure that dependent services are up and running before others start.

Mistake: Using incorrect service names or trying to access services using the wrong hostname.

Solution: Double-check the service names in your Docker-Compose file and use those names in your application for inter-service communication.

Mistake: Failing to expose necessary ports for the Angular application.

Solution: Ensure that your Angular service is exposing the intended port so that it’s accessible from the host.

Mistake: Not waiting for one service to be ready before others start to access it.

Solution: Utilize the `depends_on` directive to manage service startup order and implement Docker health checks.