How do I refer to a container by name in docker stack? - docker

Question

I am trying to deploy a simple Django/Postgress app using a docker-compose file on a docker swarm (the two containers are running on different VMs). However, I when I try establishing the connection between the two using container names (e.g. to set up Django's connection to the database) I cannot seem to use the container names. For example, if I try to run migrations from the Django container, the host name of the database container is not recognised.
This is my docker-compose.yml
version: '3.7'
services:
db:
image: postgres:10
environment:
POSTGRES_DB: "random"
POSTGRES_USER: "random"
POSTGRES_PASSWORD: "random"
app:
image: "app_server"
build:
context: ./app_server
links:
- db
environment:
DATABASE_URL: 'psql://random:random#db:5432/random'
and this is the database connection config in Django's settings.py
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.postgresql_psycopg2',
'NAME': 'random',
'USER': 'random',
'PASSWORD': 'random',
'HOST': 'db',
'PORT': '5432',
}
}
Is there a way in which I can make the Django app automatically aware of the IP of the database service?
I tried using the "name:" parameter in the service configuration, but the didn't work.
Any help is highly appreciated!