Docker-Compose, How To Connect Java Application With Custom Docker Network On Redis Container

Question

I have a java application, that connects through external database through custom docker network and I want to connect a Redis container.

docker-redis github topic

I tried the following on the application config:

1 localhost:6379
2 app_redis://app_redis:6379 
3 redis://app_redis:6379

nothing works on my setup

docker network setup:

    docker network create -d bridge --subnet 192.168.0.0/24 --gateway 192.168.0.1 mynet

Connect to a Database Running on Your Docker Host

PS: this might be off-topic, how I can add the network on docker-compose instead of external

docker-compose:

    services:
        app-kotin:
            build: ./app
            container_name: app_server
            restart: always
            working_dir: /app
            command: java -jar app-server.jar
            ports:
                - 3001:3001
            links:
              - app-redis
            networks: 
                - front
        app-redis:
            image: redis:5.0.9-alpine
            container_name: app-redis
            expose:
                - 6379 

    networks:    
        front:        
            external:
                name: mynet

with the setup above how can I connect through a Redis container?

David Maze · Accepted Answer · 2020-04-25 00:17:36Z

1

Both containers need to be on the same Docker network to communicate with each other. The app-kotin container is on the front network, but the app-redis container doesn't have a networks: block and so goes onto an automatically-created default network.

The simplest fix from what you have is to also put the app-redis container on to the same network:

    app-redis:
        image: redis:5.0.9-alpine
        networks:
            - front

The Compose service name app-redis will then be usable as a host name, from other containers on the same network.

You can simplify this setup considerably. You don't generally need to manually specify IP configuration for the Docker-private networks. Compose can create the network for you, and in fact it will create a network named default for you. (Networking in Compose discusses this further.) links: and expose: aren't used in modern Docker networking; Compose can provide a default container_name: for you; and you don't need to repeat the working_dir: or command: from the image. Removing all of that would leave you with:

version: '3'
services:
  app-kotin:
    build: ./app
    restart: always
    ports:
      - '3001:3001'
  app-redis:
    image: redis:5.0.9-alpine

The server container will be able to use the other container's Compose service name app-redis as a host name, even with this minimal configuration.

answered Apr 25, 2020 at 0:17

David Maze

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2 Comments

Victor Harlan Lacson Over a year ago

adding redis service to the same network. it works now. and using the service name as the host-name in the app configuration but using the default network created by docker-compose, connecting to host-container db isnt working. can you show the right way to configure a network, instead of using externally created docker network, I configure it using docker-compose? thanks, greatly appreciated.

David Maze Over a year ago

If you have a database running on the non-Compose mynet network then you do need a top-level networks: block like you originally had pointing at it, but you can use that block to configure the default network instead of creating a new network.

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