Docker Compose Volumes — Persisting Data and Sharing Files

Named volumes (recommended for data persistence):
  → Created and managed by Docker
  → Survive container restarts and recreations
  → Not tied to a specific host directory — portable
  → Use for: database data, Redis persistence, uploaded files

Bind mounts (for development):
  → Maps a host directory into the container
  → Changes on the host are immediately visible in the container
  → Use for: development hot-reload, sharing config files
  → DO NOT use in production — host path must exist

tmpfs mounts (in-memory):
  → Stored in host memory, not on disk
  → Cleared when container stops
  → Use for: temporary data, secrets that should never touch disk

# Without a volume: SQL Server data is lost when the container is recreated
# With a named volume: data persists across docker compose down / up

services:
  sqlserver:
    image: mcr.microsoft.com/mssql/server:2022-latest
    environment:
      - ACCEPT_EULA=Y
      - SA_PASSWORD=${DB_PASSWORD}
    volumes:
      - sqlserver-data:/var/opt/mssql  # named volume → SQL Server data directory
    healthcheck:
      test: /opt/mssql-tools/bin/sqlcmd -S localhost -U sa -P ${DB_PASSWORD} -Q "SELECT 1"
      interval: 10s
      retries: 10
      start_period: 30s

  redis:
    image: redis:7-alpine
    command: redis-server --appendonly yes  # enable Redis AOF persistence
    volumes:
      - redis-data:/data  # named volume → Redis data directory

volumes:
  sqlserver-data:   # Docker manages this directory
  redis-data:

# Development compose override — hot-reload with volume-mounted source code
# File: docker-compose.override.yml (applied on top of docker-compose.yml in development)

services:
  prescription-service:
    build:
      context: ./src/Services/PrescriptionService
      dockerfile: Dockerfile
    volumes:
      # Mount source code for hot-reload (dotnet watch)
      - ./src/Services/PrescriptionService:/app/src:ro
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
      - DOTNET_USE_POLLING_FILE_WATCHER=true
    command: ["dotnet", "watch", "run", "--project", "src/PrescriptionService.csproj"]

# docker-compose.override.yml is loaded automatically alongside docker-compose.yml
# For production: docker compose -f docker-compose.yml up (ignores override)

# Mount configuration files into containers as read-only
# Useful for: Nginx config, certificates, appsettings overrides

services:
  nginx:
    image: nginx:alpine
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro  # :ro = read-only
      - ./nginx/ssl:/etc/nginx/ssl:ro

  prescription-service:
    image: clinical/prescription-service:latest
    volumes:
      # Override appsettings with environment-specific file (read-only)
      - ./config/appsettings.Integration.json:/app/appsettings.Integration.json:ro

# Use case: prescription-service writes PDFs, nginx serves them
# Both share the same volume

services:
  prescription-service:
    image: clinical/prescription-service:latest
    volumes:
      - prescription-pdfs:/app/generated-pdfs  # writes PDFs here

  nginx:
    image: nginx:alpine
    volumes:
      - prescription-pdfs:/usr/share/nginx/html/pdfs:ro  # reads from same volume (read-only)
    # nginx serves /pdfs/prescription-{id}.pdf directly without routing through the API

volumes:
  prescription-pdfs:

# List all volumes
docker volume ls

# Inspect a specific volume (shows mount point on host)
docker volume inspect clinical_sqlserver-data

# Remove a specific volume (WARNING: deletes data)
docker volume rm clinical_sqlserver-data

# Remove all unused volumes (dangerous — removes orphaned volumes)
docker volume prune

# Remove everything (containers, networks, volumes) — full reset
docker compose down -v
# -v removes named volumes — data is DELETED
# Without -v: containers stop but volumes persist (data preserved)

# Backup a named volume
docker run --rm \
  -v clinical_sqlserver-data:/data \
  -v $(pwd)/backup:/backup \
  alpine tar czf /backup/sqlserver-backup.tar.gz -C /data .

# Restore from backup
docker run --rm \
  -v clinical_sqlserver-data:/data \
  -v $(pwd)/backup:/backup \
  alpine tar xzf /backup/sqlserver-backup.tar.gz -C /data

# Development: use bind mounts + named volumes (convenience over isolation)
# Testing: use tmpfs (fast, clean slate every run)
# Production: named volumes with backup strategy (or external managed storage)

# Testing compose (fastest startup, no persistence between test runs):
services:
  sqlserver:
    image: mcr.microsoft.com/mssql/server:2022-latest
    tmpfs:
      - /var/opt/mssql/data  # in-memory — test data lost when container stops
    # Fast startup, clean state for each test run

  redis:
    image: redis:7-alpine
    tmpfs:
      - /data  # in-memory Redis — no persistence needed for tests