Docker Database Configuration Skill

Overview

This skill configures database containers following best practices for:

• Security (passwords, network isolation)
• Persistence (named volumes)
• Health checks
• Initialization scripts
• Backup and restore

Supported Databases

• PostgreSQL
• MySQL/MariaDB
• MongoDB
• Redis

Process

1. Consult Documentation

Read 05-databases.md for:

• Image versions
• Environment variables
• Health check configurations
• Volume paths
• Initialization patterns

2. Generate Configuration

PostgreSQL Configuration

services:
  postgres:
    image: postgres:16-alpine
    container_name: postgres
    restart: unless-stopped
    shm_size: 256mb
    environment:
      POSTGRES_USER: ${DB_USER:-appuser}
      POSTGRES_PASSWORD: ${DB_PASSWORD}
      POSTGRES_DB: ${DB_NAME:-appdb}
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./init-scripts:/docker-entrypoint-initdb.d
    ports:
      - "127.0.0.1:5432:5432"
    networks:
      - database
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${DB_USER:-appuser} -d ${DB_NAME:-appdb}"]
      interval: 10s
      timeout: 5s
      retries: 5
      start_period: 30s

volumes:
  postgres_data:

networks:
  database:
    internal: true

MySQL Configuration

services:
  mysql:
    image: mysql:8.0
    container_name: mysql
    restart: unless-stopped
    environment:
      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
      MYSQL_DATABASE: ${DB_NAME}
      MYSQL_USER: ${DB_USER}
      MYSQL_PASSWORD: ${DB_PASSWORD}
    volumes:
      - mysql_data:/var/lib/mysql
      - ./init-scripts:/docker-entrypoint-initdb.d
    ports:
      - "127.0.0.1:3306:3306"
    command: >
      --default-authentication-plugin=mysql_native_password
      --character-set-server=utf8mb4
      --collation-server=utf8mb4_unicode_ci
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "root", "-p${MYSQL_ROOT_PASSWORD}"]
      interval: 10s
      timeout: 5s
      retries: 5

volumes:
  mysql_data:

MongoDB Configuration

services:
  mongodb:
    image: mongo:7
    container_name: mongodb
    restart: unless-stopped
    environment:
      MONGO_INITDB_ROOT_USERNAME: ${MONGO_USER}
      MONGO_INITDB_ROOT_PASSWORD: ${MONGO_PASSWORD}
      MONGO_INITDB_DATABASE: ${MONGO_DB}
    volumes:
      - mongo_data:/data/db
      - mongo_config:/data/configdb
    ports:
      - "127.0.0.1:27017:27017"
    healthcheck:
      test: ["CMD", "mongosh", "--eval", "db.adminCommand('ping')"]
      interval: 10s
      timeout: 5s
      retries: 5

volumes:
  mongo_data:
  mongo_config:

Redis Configuration

services:
  redis:
    image: redis:7-alpine
    container_name: redis
    restart: unless-stopped
    command: >
      redis-server
      --appendonly yes
      --maxmemory 256mb
      --maxmemory-policy allkeys-lru
      --requirepass ${REDIS_PASSWORD}
    volumes:
      - redis_data:/data
    ports:
      - "127.0.0.1:6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "-a", "${REDIS_PASSWORD}", "ping"]
      interval: 10s
      timeout: 5s
      retries: 5

volumes:
  redis_data:

Connection Strings

PostgreSQL

DATABASE_URL=postgresql://user:password@db:5432/dbname

MySQL

DATABASE_URL=mysql://user:password@db:3306/dbname

MongoDB

MONGO_URI=mongodb://user:password@mongodb:27017/dbname?authSource=admin

Redis

REDIS_URL=redis://:password@redis:6379

Backup Commands

# PostgreSQL
docker compose exec -T db pg_dumpall -c -U appuser > backup.sql

# MySQL
docker compose exec -T db mysqldump -u root -p"$PASS" --all-databases > backup.sql

# MongoDB
docker compose exec -T db mongodump --archive --gzip > backup.gz

# Redis (if persistence enabled)
docker compose exec redis redis-cli -a "$PASS" BGSAVE

Restore Commands

# PostgreSQL
docker compose exec -T db psql -U appuser -d appdb < backup.sql

# MySQL
docker compose exec -T db mysql -u root -p"$PASS" < backup.sql

# MongoDB
docker compose exec -T db mongorestore --archive --gzip < backup.gz

Best Practices

1. Always use named volumes for data persistence
2. Bind to localhost only (127.0.0.1) unless external access needed
3. Use internal networks to isolate database traffic
4. Implement health checks for dependency management
5. Store credentials in .env or Docker secrets
6. Use initialization scripts for schema setup
7. Regular backups before any risky operations