flask-docker-swarm/docker-compose-swarm.yml

# Image: Instead of referencing the local build directory, we are now using an image to set the context
# Deploy: We added a deploy keyword to configure the number of replicas, restart_policy, and placement contstraints for each service
# REFERENCE: https://docs.docker.com/compose/compose-file/

version: '3.6'

services:

  web:
    image: androiddrew/flask-docker-swarm_web:latest
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
      placement:
        constraints: [node.role == worker]
    expose:
      - 5000
    environment:
      - FLASK_ENV=production
      - APP_SETTINGS=project.config.ProductionConfig
      - DB_USER=postgres
      - DB_PASSWORD=postgres
    #  - SECRET_CODE=myprecious
    # here we are going to use docker secrets to keep everything safe
    #see the secrets section below
    secrets:
      - secret_code
    depends_on:
      - db
    networks:
      - app
    # We can add a health check to either a conmpose file or Dockerfile https://docs.docker.com/engine/reference/builder/#healthcheck
    healthcheck:
      # Test is the actual command that will be run to check the health status
      # It should return 0 (Healthy) or 1 (Unhealthy)
      test: curl --fail http://localhost:5000/ping || exit 1
      interval: 10s
      timeout: 2s
      retries: 5

  db:
    image: androiddrew/flask-docker-swarm_db:latest
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
      placement:
        #constraints: [node.role == manager]
        constraints: [node.role == worker]
    volumes:
      - data-volume:/var/lib/postgresql/data
    expose:
      - 5432
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
    networks:
      - app

  nginx:
    image: androiddrew/flask-docker-swarm_nginx:latest
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
      placement:
        constraints: [node.role == worker]
    ports:
      - 80:80
    depends_on:
      - web
    networks:
      - app

  visualizer:
    image: dockersamples/visualizer:latest
    ports:
      - 8080:8080
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    deploy:
      placement:
        constraints: [node.role == manager]
    networks:
      - app

# We are now using an overlay network to connect multiple Docker engines across each host and enable communication between Swarm services
networks:
  app:
    driver: overlay

volumes:
  #data-volume:
  #  driver: local
  data-volume:
    driver: local
    driver_opts:
      type: nfs
      o: addr=nas1.androiddrew.com,rw
      device: ":/volume1/expanse/flask_data"
# Secrets can be configured in either external or file-based manner
secrets:
  secret_code:
    external: true