docker-compose.postgres.yml

# PostgreSQL overlay. Layered onto docker-compose.yml with a second -f, which merges the two
# service maps: `app` gains its database dependency and connection environment, and the `db`
# service plus its volume appear. Kept separate rather than behind a compose profile because a
# profile cannot add a depends_on edge to an already-declared service.
services:
  app:
    depends_on:
      db:
        condition: service_healthy
    environment:
      # Host and port are both overridden; user, password and database reach the container through
      # env_file. There is deliberately no DATABASE_URL here — nothing in the application reads one,
      # so it would be a knob that looks like the connection string and changes nothing.
      POSTGRES_HOST: db
      # POSTGRES_PORT carries two meanings and only one of them belongs here. In .env it is the
      # HOST port the db service publishes on — a developer whose 5432 is already taken sets it to
      # something else, which is exactly what `make smoke` does by defaulting it to 15432. Inside
      # the network the container always listens on 5432, so letting the .env value through
      # env_file made the app dial db:<host port> and die with "connection refused" during the
      # entrypoint's alembic run. Measured: a project with POSTGRES_PORT=15433 in .env could not
      # bring up its own stack at all.
      POSTGRES_PORT: 5432

  db:
    image: postgres:15
    environment:
      POSTGRES_USER: ${POSTGRES_USER}
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
      POSTGRES_DB: ${POSTGRES_DB}
    ports:
      - "${POSTGRES_PORT:-5432}:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
      interval: 5s
      timeout: 5s
      retries: 5
      start_period: 10s

volumes:
  postgres_data: