docker-compose.yml

# docker-compose.yml file version
version: '2'

# Data volume for Mongo
volumes:
  mongostorage:

# Services (Docker containers)
services:

  # Mongo Database service
  mongodb:
    # Give it a name 
    container_name: mongodb_container
    # https://hub.docker.com/r/alexpunct/mongo/
    image: alexpunct/mongo:3.4
    # We use mongostorage data volume and we will use the /data/db path for the database inside the container
    volumes: 
    - mongostorage:/data/db
    # Expose a MongoDB port to connect to, defined by the MONGODB_EXPOSED_PORT environment variable
    # and map this port to the 27017 internal port which is what MongoDB uses
    ports:
    - "${MONGODB_EXPOSED_PORT}:27017"
    # Passing environment variables from the host to the container. 
    # Our container expects the following variables (as explained here: https://hub.docker.com/r/alexpunct/mongo/)
    environment:
    MONGODB_ADMIN_USER: $MONGODB_ADMIN_USER
    MONGODB_ADMIN_PASS: $MONGODB_ADMIN_PASS
    MONGODB_APPLICATION_DATABASE: $MONGODB_APPLICATION_DATABASE
    MONGODB_APPLICATION_USER: $MONGODB_APPLICATION_USER
    MONGODB_APPLICATION_PASS: $MONGODB_APPLICATION_PASS
 
  # REST API service
  restapi:
    # Give it a name
    container_name: restapi_container
    # https://hub.docker.com/r/linuxenko/mongo-rest/
    image: linuxenko/mongo-rest
    # The port that our API will have exposed so we can connect to
    ports:
    - "${REST_API_EXPOSED_PORT}:3000"
    # This field creates a hosts file entry in our container that points to the mongodb service
    # so we can access it with the hostname mongo as in http://mongo:3000 from this container.
    # It also tells the mongodb service to allow our service to connect to it (if we hand't have exposed a port already)
    # Ultimately, it makes sure that mongodb starts before our restaapi service
    links:
    - mongodb:mongo
    # Environment variables passed to the container.
    environment:
    ME_CONFIG_APIKEY: $REST_API_APIKEY
    ME_CONFIG_DBSTRING: "mongodb://${MONGODB_APPLICATION_USER}:${MONGODB_APPLICATION_PASS}@mongo:27017/${MONGODB_APPLICATION_DATABASE}"