docker-compose.yml

version: '3'
services:
  mongo:
    image: mongo
    # volumes:
    #   - ./db:/data/db # uncomment this line for database persistency
    ports:
      - "27017:27017"
  server:
    build:
      context: .
      dockerfile: Dockerfile.dev
    ports: 
      - "4000:4000"
    volumes:
      - /app/node_modules
      - .:/app
    depends_on:
      - mongo
  
#  In our docker-compose.yml we have added 'database' as a name to our MongoDB service. Now, we can use this as a reference while connecting to MongoDB. So in our index.js we can change mongoose.connect('localhost:27017/myapp') to mongoose.connect('database:27017/myapp')
#  Volumes allow you to mount folders on the host machine to folders in the container. Meaning, when something inside the container refers to a folder, it will actually be accessing a folder on the host machine. This is especially helpful for database containers because containers are meant to be disposable. With a mount to the physical folder on the host machine, you’ll be able to destroy a container and rebuild it and the data files for the container will still be there on the host machine. So add a volume tag in the db section mounting the /data/db folder in the container (where Mongo stores its data) to the db folder in your application’s root folder