Multi-Container Template¶

This template is for deploying multiple services together (app + database, app + cache, etc.).

Use Cases¶

Web app with PostgreSQL database
API with Redis cache
Full-stack application with multiple services
Microservices architecture

Template¶

docker-compose.yml

version: '3.8'

services:
  # Your application
  app:
    build: .
    container_name: my-app
    restart: unless-stopped
    environment:
      - DATABASE_URL=postgresql://postgres:password@db:5432/mydb
      - REDIS_URL=redis://cache:6379
    depends_on:
      - db
      - cache
    labels:
      # Enable Traefik for this container
      - traefik.enable=true

      # Router configuration
      - traefik.http.routers.my-app.rule=Host(`app.egygeeks.com`)
      - traefik.http.routers.my-app.entrypoints=websecure
      - traefik.http.routers.my-app.tls.certresolver=letsencrypt

      # Service configuration (port your app listens on)
      - traefik.http.services.my-app.loadbalancer.server.port=3000
    networks:
      - traefik_public
      - internal

  # PostgreSQL Database
  db:
    image: postgres:15-alpine
    container_name: my-app-db
    restart: unless-stopped
    environment:
      - POSTGRES_DB=mydb
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=password
    volumes:
      - postgres-data:/var/lib/postgresql/data
    networks:
      - internal

  # Redis Cache (optional)
  cache:
    image: redis:7-alpine
    container_name: my-app-cache
    restart: unless-stopped
    networks:
      - internal

volumes:
  postgres-data:

networks:
  traefik_public:
    external: true
  internal:
    driver: bridge

Customization Steps¶

1. Replace App Name¶

Find and replace my-app throughout:

Container names: my-app, my-app-db, my-app-cache
Router names: my-app
Service names: my-app

2. Set Your Domain¶

- traefik.http.routers.my-app.rule=Host(`yourdomain.com`)

3. Configure Database¶

Change database credentials:

Never use default passwords in production!

Replace password with a strong password. Store in .env file on server.

environment:
  - POSTGRES_PASSWORD=your-strong-password-here

Update connection string:

- DATABASE_URL=postgresql://postgres:your-strong-password-here@db:5432/mydb

4. Remove Optional Services¶

Don't need Redis? Remove the cache service:

# Remove this entire section
cache:
  image: redis:7-alpine
  ...

And remove from app dependencies:

depends_on:
  - db
  # Remove: - cache

Network Architecture¶

This template uses two networks for security:

traefik_public (External)¶

Only the app service connects here
Allows Traefik to route traffic to your app
External network shared across all apps

internal (Private)¶

All services connect here
App communicates with database/cache
Never exposed to the internet
Database and cache are NOT accessible externally

Internet → Traefik → [traefik_public] → App → [internal] → Database/Cache

Security Best Practice

Only your application service should be on traefik_public. Never expose databases or caches directly to Traefik.

Database Options¶

PostgreSQL (Default)¶

db:
  image: postgres:15-alpine
  environment:
    - POSTGRES_DB=mydb
    - POSTGRES_USER=postgres
    - POSTGRES_PASSWORD=password
  volumes:
    - postgres-data:/var/lib/postgresql/data

MySQL¶

db:
  image: mysql:8-debian
  environment:
    - MYSQL_DATABASE=mydb
    - MYSQL_USER=user
    - MYSQL_PASSWORD=password
    - MYSQL_ROOT_PASSWORD=rootpassword
  volumes:
    - mysql-data:/var/lib/mysql

MongoDB¶

db:
  image: mongo:7
  environment:
    - MONGO_INITDB_DATABASE=mydb
    - MONGO_INITDB_ROOT_USERNAME=admin
    - MONGO_INITDB_ROOT_PASSWORD=password
  volumes:
    - mongo-data:/data/db

Environment Variables¶

Using .env File (Recommended)¶

Create .env file on server:

.env

DATABASE_URL=postgresql://postgres:strong-password@db:5432/mydb
REDIS_URL=redis://cache:6379
API_KEY=your-secret-key

Reference in docker-compose.yml:

services:
  app:
    env_file:
      - .env

Never commit .env to git

Add .env to .gitignore. Store secrets only on the server.

Complete Example: Next.js + PostgreSQL¶

docker-compose.yml

version: '3.8'

services:
  app:
    build: .
    container_name: nextjs-app
    restart: unless-stopped
    environment:
      - DATABASE_URL=postgresql://postgres:${DB_PASSWORD}@db:5432/appdb
    depends_on:
      - db
    labels:
      - traefik.enable=true
      - traefik.http.routers.nextjs-app.rule=Host(`myapp.egygeeks.com`)
      - traefik.http.routers.nextjs-app.entrypoints=websecure
      - traefik.http.routers.nextjs-app.tls.certresolver=letsencrypt
      - traefik.http.services.nextjs-app.loadbalancer.server.port=3000
    networks:
      - traefik_public
      - internal

  db:
    image: postgres:15-alpine
    container_name: nextjs-app-db
    restart: unless-stopped
    environment:
      - POSTGRES_DB=appdb
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=${DB_PASSWORD}
    volumes:
      - postgres-data:/var/lib/postgresql/data
    networks:
      - internal

volumes:
  postgres-data:

networks:
  traefik_public:
    external: true
  internal:
    driver: bridge

With .env file:

.env

DB_PASSWORD=super-secret-password-123

Deployment¶

After creating your configuration:

Create .env file on server with secrets
Copy the GitHub Actions workflow template
Push to GitHub
Deployment runs automatically

Or deploy manually on the server:

docker compose up -d

Troubleshooting¶

App can't connect to database¶

Check container names match connection string:

# Connection string uses 'db' as hostname
DATABASE_URL=postgresql://postgres:password@db:5432/mydb

# Service must be named 'db'
db:
  image: postgres:15-alpine

Verify both are on same network:

docker network inspect my-app_internal

Database data lost after restart¶

Ensure volume is configured:

volumes:
  - postgres-data:/var/lib/postgresql/data

volumes:
  postgres-data:  # Must be declared at bottom

Port conflicts¶

Each service needs unique ports internally, but don't expose database ports:

# ❌ Don't do this
db:
  ports:
    - "5432:5432"  # Never expose database ports!

# ✅ Do this instead
db:
  # No ports section - only accessible via internal network

Single Container Template Deployment Workflow