Unknown Host Exception

Question

Unknown HostException Exception on Docker Container.

I have multiples services, my docker-compose has the following code:

version: '3.5'

    services:


      reservation:
        container_name: sp-app-reservation
        image: swimming-pool/reservation-service
        environment:
         - SPRING_PROFILES_ACTIVE=dev
        ports:
         - 8181:8182
        depends_on:
         - notification
        network_mode: host
        restart: always


      web:
        container_name: sp-app-web-ui
        image: swimming-pool/web-ui-service
        environment:
         - SPRING_PROFILES_ACTIVE=dev
        ports:
         - 8080:8081
        depends_on:
         - notification
         - reservation
         - fileupload
        network_mode: host
        restart: always  

      eureka:
        container_name: sp-app-eureka
        image: swimming-pool/discovery-service
        environment:
         - SPRING_PROFILES_ACTIVE=dev
         - SERVICE_PORT_RESERVATION=8181
         - SERVICE_PORT_FILEUPLOAD=8686
         - SERVICE_PORT_WEB=8080
        ports:
         - 8761:8762
        network_mode: host
        restart: always

I'm using Rest Template to invoke from Web service to Reservation service using the " http://sp-app-reservation:8182/rest/reservation ".

I'm facing the below exception, and i can see my container running with the same name.

org.springframework.web.client.ResourceAccessException: I/O error on GET 
request for "http://sp-app-reservation:8182/rest/reservation/":
sp-app-reservation;  nested exception is java.net.UnknownHostException: 
sp-app-reservation

Answer 1

You are using network_mode: host , so you need to configure host record "sp-app-reservation" on the host OS level (for example "hardcode" it in /etc/hosts ).

Better option will be to create docker network, where you can use docker container names and you will publish only selected ports to host OS.