.dockerignore

node_modules

.gitignore

node_modules

docker-compose.yml

version: '3'
services:
  db:
    image: mongo
    # ports:
    #   - "27017:27017"
  my-project:
    image: my-project
    build:
      context: .
    links:
      - db

Dockerfile

FROM node:6.9.4-alpine

WORKDIR /app

ADD package.json ./
RUN npm install --production
ADD server.js ./

CMD npm start

package.json

{
  "name": "test-dc",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "start": "node server.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "mongodb": "^2.2.25"
  }
}

server.js

const MongoClient = require('mongodb').MongoClient
const DATABASE_URL = process.env.DATABASE_URL || 'mongodb://db:27017/myproject'

function connect (url) {
  return new Promise((resolve, reject) => {
    MongoClient.connect(url, (err, db) => {
      if (err) reject(err)
      else resolve(db)
    })
  })
}

function wait (ms, val) {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve(val)
    })
  }, ms)
}

function retry (coroutine, tries, interval = 500) {
  return Promise.resolve(coroutine())
    .catch(err => {
      if (tries) return wait(interval, () => retry(coroutine, tries - 1))
      else throw err
    })
}


retry(() => connect(DATABASE_URL), 5).then(db => {
  console.log(`Connected to database [${DATABASE_URL}]`)
  
  db.close()
})