docker-compose.yml

# ============================================================
# docker-compose.yml
#
# Starts three services with one command: docker compose up
#
# SERVICES
#   db    — PostgreSQL 16 (persistent storage)
#   app   — FastAPI application (built from Dockerfile)
#   redis — Redis 7 (stretch goal, used in W4)
#
# NETWORKING
#   Docker creates a private network for these services.
#   Services reach each other by service name as hostname:
#     app → db    via  host "db",    port 5432
#     app → redis via  host "redis", port 6379
#   Your laptop reaches them via localhost:PORT (mapped below).
#
# VOLUMES
#   postgres_data — named volume; survives docker compose down.
#                   Data deleted only by: docker compose down -v
# ============================================================

services:

  # ── PostgreSQL ────────────────────────────────────────────
  db:
    image: postgres:16-alpine
    restart: unless-stopped
    environment:
      POSTGRES_DB:       tasks
      POSTGRES_USER:     taskuser
      POSTGRES_PASSWORD: taskpass
    volumes:
      - postgres_data:/var/lib/postgresql/data
      # NOTE: No init.sql mount needed anymore —
      # SQLAlchemy creates the table on app startup via
      # Base.metadata.create_all(engine) in main.py lifespan
    ports:
      - "5432:5432"     # localhost:5432 → container:5432
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U taskuser -d tasks"]
      interval: 5s
      timeout: 5s
      retries: 10       # give Postgres time to start on first launch

  # ── FastAPI app ───────────────────────────────────────────
  app:
    build: .            # reads Dockerfile in current directory
    restart: unless-stopped
    environment:
      # SQLAlchemy connection string format:
      #   postgresql+psycopg2://USER:PASS@HOST:PORT/DBNAME
      # HOST = "db" (the service name above, Docker DNS resolves it)
      DATABASE_URL: postgresql+psycopg2://taskuser:taskpass@db:5432/tasks
    ports:
      - "8000:8000"     # localhost:8000 → container:8000
    depends_on:
      db:
        condition: service_healthy   # wait for Postgres healthcheck to pass
    env_file:
      - path: .env
        required: false  # .env is optional (docker-compose env vars take priority)

  # ── Redis (Stretch / W4) ──────────────────────────────────
  redis:
    image: redis:7-alpine
    restart: unless-stopped
    ports:
      - "6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s
      timeout: 3s
      retries: 5

# ── Named volumes ─────────────────────────────────────────────
volumes:
  postgres_data:
    # Docker manages the storage location on your machine.
    # Windows: C:\Users\<user>\AppData\Local\Docker\...
    # Mac/Linux: /var/lib/docker/volumes/...