Question

You inherit the following docker-compose.yml for a network automation stack:

services:
  nautobot:
    image: networktocode/nautobot:latest
    depends_on:
      - db
      - redis
    volumes:
      - nautobot_media:/opt/nautobot/media
    networks:
      - backend
    ports:
      - "8080:8080"
  db:
    image: postgres:13
    volumes:
      - db_data:/var/lib/postgresql/data
    networks:
      - backend
  redis:
    image: redis:6
    networks:
      - backend
networks:
  backend:
volumes:
  nautobot_media:
  db_data:

The nautobot container starts but immediately errors with a database connection refused, even though the db container is running. Which statement correctly explains the behavior of this file?

Accepted Answer

depends_on only controls container startup order, not readiness, so nautobot may start before PostgreSQL is accepting connections.

Answer

The db service is unreachable because it is on the 'backend' network while nautobot only publishes port 8080 to the host.

Answer

Named volumes cannot be shared across services, so db_data prevents PostgreSQL from initializing and rejecting connections.

Answer

Without a 'links:' directive, nautobot cannot resolve the db service name, causing the connection to be refused.