A simple heroku-docker example for nodejs with development, CI and deployment instructions

This README acts as a quick start guide to setting up and using heroku-docker, the repo itself contains the final result.

Install some deps

• docker-compose
• heroku toolbelt

Via the CLI, install the heroku-docker plugin

heroku plugins:install heroku-docker

We'll also assume you'll have this code in a repo on github

Create a package.json

{
  "name": "heroku-docker-nodejs",
  "private": true,
  "version": "0.0.0",
  "dependencies": {
    "express": "^4.13.3"
  }
}

...an app.js

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send("Hello from container land!");
});

var server = app.listen(process.env.PORT, function () {
  var port = server.address().port;
  console.log('Example app listening at http:/localhost:%s', port);
});

...an app.json describing your app

{
  "name": "nodejs-heroku-docker",
  "description": "A simple docker heroku example for nodejs",
  "image": "heroku/nodejs",
  "addons": []
}

...and a Procfile to start our app with^

web: npm install; node app.js

Now lets get the heroku toolbelt to generate us some heroku config

$ heroku docker:init
Wrote Dockerfile
Wrote docker-compose.yml

This will have created 2 files which docker-compose uses to create and run your containers. Now go and add some additional bits to your docker-compose.yml, this will allow you to share files between the host and the container during dev.

web: 
  volumes:
   - ./:/app/user/
   - /app/user/node_modules

Then run

$ docker-compose build

Note if the Dockerfile has changed then you'll have to rerun the above command, to rebuild the container

When running the app in development the main requirement is quick restarts of your app. So instead of reloading the VM each time, we'll start a bash shell in the container and run the app manually.

$ docker-compose run --service-ports web bash

The important part above is docker-compose run web which will run a command in our docker container. --service-ports tells docker-compose that we want to setup the port mappings. You should now be seeing a bash prompt where you can start your app.

root@52697b69237b:/code# npm install
root@52697b69237b:/code# npm start

Open another terminal and run the following to hit the web server from a browser

$ open "http://$(docker-machine ip default):8080"

To deploy the VM to production first off create an app on heroku

heroku create [optional name]

Now instead of running git push heroku as you'd normally do with heroku, we instead run

heroku docker:release

As normal you can now open the app in your browser

heroku open

Next up lets setup some CI with circleci, first off create an account if you haven't already got one.

Create a simple test (ok it doesn't actually test anything but you'll get the idea)

//  ./test/index.js 
var assert = require("assert");

describe("heroku-docker-nodejs", function() {
  it("should pass test :)", function() {
    assert(true);
  });
});

Add the test script and mocha dependency to your package.json

{
  "dependencies": {
    "mocha": "^2.3.3"
  },
  "scripts": {
    "test": "mocha test/index.js"
  }
}

Next up add a circle.yml to the base of the repo and push this to github

machine:
  services:
    - docker

dependencies:
  pre:
    - sudo pip install --upgrade docker-compose==1.3.0
  override:
    - docker-compose build

test:
  override:
    - docker-compose run --service-ports web npm test

Then add the project in circleci and you should very shortly see passing test :)

We'll add postgres as an example here as it's probably the most common addon for heroku. First off add the following to your docker-compose.yml

web:
  environment:
    DATABASE_URL: 'postgres://postgres:@herokuPostgresql:5432/postgres'
  links:
    - herokuPostgresql
shell:
  environment:
    DATABASE_URL: 'postgres://postgres:@herokuPostgresql:5432/postgres'
  links:
    - herokuPostgresql
# This defines a new service called herokuPostgresql
herokuPostgresql:
  image: postgres

herokuPostgresql defines a new service which uses the postgres image from dockerhub, this is linked from the web/shell services. When you setup a link the service will be added to /etc/hosts

So the host herokuPostgresql will point to our postgres server running in another container, cool huh!

Now we'll add psql so we can connect to postgres from within our web service. To do this append the following to the Dockerfile

RUN apt-get update && apt-get install -y postgresql-client-9.3

Now rebuild the image

docker-compose build

We can now start a shell and test that we can connect to postgres.

$ docker-compose run --service-ports web bash
$ psql $DATABASE_URL

Note: The DATABASE_URL was defined in the docker-compose-yml above.

You should now be connected to the postgres server! If you want to know more about the postgres docker image see https://hub.docker.com/_/postgres/

I've also added a few scripts (just shorthands really) to the ./scripts directory

• shell - to run in development
• open - to open in a browser
• rebuild - rebuild the container
• run - to run in a production like way

• https://circleci.com/docs/continuous-deployment-with-heroku
• https://devcenter.heroku.com/articles/docker
• https://ddollar.github.io/foreman
• https://hub.docker.com/_/postgres

To samgiles and oliverbrooks for the pointers

MIT