John Jerald De Chavez

Connect Two Docker Compose

Let say you have a global/dev docker-compose on your machine with postgres, redis, and etc. You decided to use your dev docker-compose(postgres) on your new project that also running with docker-compose. On this article we're going to takcle on how to connect the two docker-compose.

Create a Docker Network

To have a connection with your two docker-compose, what we need is to create docker network. The command that we need:

docker network create your-network-name

For this article we're going to create a network with dev_network.

docker network create dev_network

Update Docker Compose files

We need to attached the network on each docker-compose, with this:

# On each containers
services:
  postgres_db
    networks:
      - dev_network # Link the network

# Below of your docker-compose.yml
networks:
  dev_network:
    name: dev_network
    external: true

So on your dev docker-compose.yml, add the dev_network

version: '3.9'

services:
  postgres_db:
    image: 'postgres:16.3-alpine3.20'
    container_name: postgres-db
    ports:
      - 5432:5432

    environment:
      POSTGRES_USER: postgres # The PostgreSQL user (useful to connect to the database)
      POSTGRES_PASSWORD: password # The PostgreSQL password (useful to connect to the database)
      # POSTGRES_DB: default_database # The PostgreSQL default database (automatically created at first launch)
    volumes:
      - ./postgres/:/database/
    networks:
      - dev_network # Link the network

  redis_db:
    image: 'redis:7.4.0-alpine'
    container_name: redis-db
    ports:
      - 6379:6379

networks:
  dev_network:
    name: dev_network
    external: true

To determine if our dev docker-compose.yml is connected to dev_network. We could use docker command with docker network inspect. Make it sure that we docker-compose stop and

docker-compose up -d

johndoe@mycomputer % docker network inspect dev_network
[
    {
        "Name": "dev_network",
        "Id": "1f1b67ad88da5f1011e9ce7b5284312104b0ea01fb451e026ce42cbd17da616b",
        "Created": "2024-11-14T09:04:07.653805582+08:00",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "192.168.97.0/24",
                    "Gateway": "192.168.97.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "a0ed9c39e85b5a1bf6c07fc976c0550c8f0f95ce1ffeea8ffe18c99fe6870d2b": {
                "Name": "postgres-db",
                "EndpointID": "bc4e3de6a18552a55fdfe90cf9c74d588768b83fe91cce66e62d0908650b8a3f",
                "MacAddress": "02:42:c0:a8:61:02",
                "IPv4Address": "192.168.97.2/24",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

Update our second docker-compose.yml with dev_network

version: "3.9"

services:
  web:
    container_name: ror-starter
    image: ror/heroku-ror:2.7.3
    ports:
      - "3000:3000"
    environment:
      RAILS_ENV: development
    volumes:
      - ./:/app/user
    networks:
      - dev_network
    extra_hosts:
      host.docker.internal: host-gateway

networks:
  dev_network:
    name: dev_network
    external: true

Again, we make it sure we docker-compose stop and

docker-compose up -d

So it should look like this:

johndoe@mycomputer % docker network inspect dev_network
[
    {
        "Name": "dev_network",
        "Id": "1f1b67ad88da5f1011e9ce7b5284312104b0ea01fb451e026ce42cbd17da616b",
        "Created": "2024-11-14T09:04:07.653805582+08:00",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                {
                    "Subnet": "192.168.97.0/24",
                    "Gateway": "192.168.97.1"
                }
            ]
        },
        "Internal": false,
        "Attachable": false,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        },
        "ConfigOnly": false,
        "Containers": {
            "8d77c05ddd533340716a2a702cf71f61d2f1f09f94e7d364c90b99e822ddfe83": {
                "Name": "ror-starter",
                "EndpointID": "0b5bf2d88a9d336ddb094461c3cdc19eea46d3c1c7c727e0ab082466aba0af55",
                "MacAddress": "02:42:c0:a8:61:03",
                "IPv4Address": "192.168.97.3/24",
                "IPv6Address": ""
            },
            "a0ed9c39e85b5a1bf6c07fc976c0550c8f0f95ce1ffeea8ffe18c99fe6870d2b": {
                "Name": "postgres-db",
                "EndpointID": "bc4e3de6a18552a55fdfe90cf9c74d588768b83fe91cce66e62d0908650b8a3f",
                "MacAddress": "02:42:c0:a8:61:02",
                "IPv4Address": "192.168.97.2/24",
                "IPv6Address": ""
            }
        },
        "Options": {},
        "Labels": {}
    }
]

Bonus Tips

• On our application code, you're probably thinking how are we going to use the dev docker-compose.yml postgres URL. Update your env DATABASE_URL with postgresql://postgres:password@postgres-db/ror_dev, we update the URI from "localhost" to "postgres-db" or the container name of your postgres.

References

• Networking in Compose