Network Two Containers

In this lab you’ll create a Docker network that you can use to connect two containers. One of the great things about a Docker network is that names and addresses are handled by Docker. On a non-default network containers can be reached by their name. Until now we’ve let Docker automatically give us a name like church_missives, but now we’ll give containers names that we want to be able to use with the --name argument.

Create a Network

The Django container needs to reach the Postgres. The Postgres container should not expose any ports to the host, it’s completely hidden from the outside world. Let’s create a Docker network:

$ docker network create mysite

Verify your network is there:

$ docker network list
NETWORK ID     NAME      DRIVER    SCOPE
9850eee009e7   bridge    bridge    local
28e6c097494d   mysite    bridge    local
a99d5edd9623   host      host      local
81a76cda7c70   none      null      local

Start Postgress

If you already have a Postgres container running, stop and remove it. We need to launch it again with the --network option to use the mysite network.

$ docker run -d --rm \
    -v $HOME/data:/var/lib/postgresql/data \
    -e POSTGRES_PASSWORD=django -e POSTGRES_DB=mysite \
    --network mysite \
    --name postgres \
    postgres:14.1

Note

Notice that port forwarding has been disabled.

Update Django’s Configuration

With Postgres started in a container named postgres you can update Django’s settings.py:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'mysite',
        'USER': 'postgres',
        'PASSWORD': 'django',
        'HOST': 'postgres',
    },
}

Rebuild and run your container on the mysite network:

$ docker run -it --rm -p 8000:8000 \
    --network mysite --name django \
    -e SECRET_KEY=mysecretkey -e PORT=8000 \
    mysite 

Note

We still need a port forward so our app is visible to the outside.

Clean Up

With your data safe, you’re free to remove the containers any time you want. Stop and remove your two running containers:

$ docker stop django postgres