[Python] Docker-Compose Error When Building Django Dockerfile: Error -2 connecting to...

I’m trying to set up an open-source status page application using the repository from Status-Page/Status-Page with Docker Compose. When I run docker-compose up -d, I encounter an error during the build process of the Django service’s Dockerfile. The error seems to occur at the Upgrade and initialize application, but I’m not sure how to debug it further or resolve it. Here’s my setup:

Dockerfile:

# Use the official Python runtime image
FROM python:3.12.3

# Create the app directory
RUN mkdir -p /opt/status-page/

# Set the working directory inside the container
WORKDIR /opt/status-page/

# Set environment variables
# Prevents Python from writing pyc files to disk
ENV PYTHONDONTWRITEBYTECODE=1
# Prevents Python from buffering stdout and stderr
ENV PYTHONUNBUFFERED=1

# Install system dependencies
RUN apt-get update && apt install -y libpq-dev gcc

# Create a system user and group
RUN adduser --system --group status-page

# Set ownership of the app directory
RUN chown -R status-page:status-page /opt/status-page/

# Upgrade pip
RUN pip install --upgrade pip

# Copy the Django project to the container
ADD status-page /opt/status-page/

# Grant execute permissions to upgrade.sh
RUN chmod +x /opt/status-page/upgrade.sh

# Install Python dependencies
RUN python -m venv /opt/status-page/venv \
&& /opt/status-page/venv/bin/pip install --no-cache-dir -r requirements.txt

# Upgrade and initialize application
RUN /opt/status-page/upgrade.sh
RUN /opt/status-page/venv/bin/python /opt/status-page/statuspage/manage.py migrate
RUN /opt/status-page/venv/bin/python /opt/status-page/statuspage/manage.py createsuperuser --noinput

# Copy Gunicorn and systemd service files
RUN cp /opt/status-page/contrib/gunicorn.py /opt/status-page/gunicorn.py \
&& cp -v /opt/status-page/contrib/*.service /etc/systemd/system/ \
&& systemctl daemon-reload

# Expose the Django port
EXPOSE 8000

# Start Gunicorn
CMD ["/opt/status-page/venv/bin/gunicorn", "-c", "/opt/status-page/gunicorn.py", "statuspage.wsgi:application"]


docker-compose.yml:

version: '3.9'

services:
# PostgreSQL service
db:
image: postgres:15
container_name: status-page-db
environment:
POSTGRES_USER: status-page
POSTGRES_PASSWORD: abcdefgh123456
POSTGRES_DB: status-page
volumes:
- postgres_data:/var/lib/postgresql/data
healthcheck:
test: ["CMD-SHELL", "pg_isready -U status-page -d status-page"]
interval: 10s
timeout: 5s
retries: 5
networks:
- status_page_network

# Redis service
redis:
image: redis:6
container_name: status-page-redis
ports:
- "6379:6379"
hostname: redis_host
healthcheck:
test: ["CMD", "redis-cli", "ping"]
interval: 10s
timeout: 5s
retries: 5
networks:
- status_page_network

# Django (Status-Page) service
django:
build: ./statuspage
container_name: status-page-django
environment:
DATABASE_NAME: status-page
DATABASE_USER: status-page
DATABASE_PASSWORD: abcdefgh123456
DATABASE_HOST: db
REDIS_HOST: redis_host
REDIS_PORT: 6379
SECRET_KEY: Pv)hkWbYxkpaD_dh$ULGa6MF#ADn6&=MU&#v5cjRyViuTbPHuG
volumes:
- ./status-page:/opt/status-page
- status-page-venv:/opt/status-page/venv
depends_on:
db:
condition: service_healthy
redis:
condition: service_healthy
expose:
- "8000"
command: /opt/status-page/venv/bin/gunicorn -c /opt/status-page/gunicorn.py statuspage.wsgi:application
networks:
- status_page_network

# Nginx service
nginx:
image: nginx:latest
container_name: status-page-nginx
volumes:
- ./nginx.conf:/etc/nginx/nginx.conf
- ./status-page/static:/usr/share/nginx/html/static
ports:
- "80:80"
- "443:443"
depends_on:
- django
networks:
- status_page_network
environment:
- NGINX_HOST=status-page.example.com
- NGINX_PORT=80

volumes:
postgres_data:
status-page-venv:

networks:
status_page_network:
driver: bridge


Configuration (snippet):

ALLOWED_HOSTS = ['*']

# PostgreSQL database configuration. See the Django documentation for a complete list of available parameters:
# https://docs.djangoproject.com/en/stable/ref/settings/#databases
DATABASE = {
'NAME': 'status-page', # Database name
'USER': 'status-page', # PostgreSQL username
'PASSWORD': 'abcdefgh123456', # PostgreSQL password
'HOST': 'db', # Database server
'PORT': '5432', # Database port (leave blank for default)
'CONN_MAX_AGE': 300, # Max database connection age
}

# Redis database settings. Redis is used for caching and for queuing background tasks. A separate configuration exists
# for each. Full connection details are required.
REDIS = {
'tasks': {
'HOST': 'redis_host',
'PORT': 6379,
# Comment out `HOST` and `PORT` lines and uncomment the following if using Redis Sentinel
# 'SENTINELS': [('mysentinel.redis.example.com', 6379)],
# 'SENTINEL_SERVICE': 'status-page',
'PASSWORD': '',
'DATABASE': 0,
'SSL': False,
# Set this to True to skip TLS certificate verification
# This can expose the connection to attacks, be careful
# 'INSECURE_SKIP_TLS_VERIFY': False,
},
'caching': {
'HOST': 'redis_host',
'PORT': 6379,
# Comment out `HOST` and `PORT` lines and uncomment the following if using Redis Sentinel
# 'SENTINELS': [('mysentinel.redis.example.com', 6379)],
# 'SENTINEL_SERVICE': 'netbox',
'PASSWORD': '',
'DATABASE': 1,
'SSL': False,
# Set this to True to skip TLS certificate verification
# This can expose the connection to attacks, be careful
# 'INSECURE_SKIP_TLS_VERIFY': False,
}
}


The Problem: redis.exceptions.ConnectionError: Error -2 connecting to redis:6379. Name or service not known.

What I’ve Tried:

1. I updated DATABASE_HOST to db in the environment variables of the docker-compose.yml to match the service name.
2. I confirmed that the depends_on with service_healthy conditions are set for db and redis, but these only apply at runtime, not during the build.

How to solve it?

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