The node-on-heroku-guide from sethbergman

Node.js on Heroku Guide

A barebones Node.js app using Express 4.

This application supports the Getting Started with Node on Heroku article - check it out.

Running Locally

Prepare the app

git clone https://github.com/heroku/node-js-getting-started.git
cd node-js-getting-started

Setup Remote Repository

git remote -v
origin  https://github.com/heroku/node-js-getting-started.git (fetch)
origin  https://github.com/heroku/node-js-getting-started.git (push)

git remote set-url --push origin https://github.com/sethbergman/node-on-heroku-guide.git

git remote -v
origin  https://github.com/heroku/node-js-getting-started.git (fetch)
origin  https://github.com/sethbergman/node-on-heroku-guide.git (push)

Deploy the app

heroku create

Now deploy your code:

git push heroku master

The application is now deployed. Ensure that at least one instance of the app is running:

heroku ps:scale web=1

Now visit the app at the URL generated by its app name. As a handy shortcut, you can open the website as follows:

heroku open

View logs

Heroku treats logs as streams of time-ordered events aggregated from the output streams of all your app and Heroku components, providing a single channel for all of the events.

View information about your running app using one of the logging commands, heroku logs:

heroku logs --tail

Visit your application in the browser again, and you’ll see another log message generated. Press Control+C to stop streaming the logs.

Define a Procfile

Use a Procfile, a text file in the root directory of your application, to explicitly declare what command should be executed to start your app.

The Procfile in the example app you deployed looks like this:

web: node index.js

This declares a single process type, web, and the command needed to run it. The name web is important here. It declares that this process type will be attached to the HTTP routing stack of Heroku, and receive web traffic when deployed.

Procfiles can contain additional process types. For example, you might declare one for a background worker process that processes items off of a queue.

Scale the app

Right now, your app is running on a single web dyno. Think of a dyno as a lightweight container that runs the command specified in the Procfile.

You can check how many dynos are running using the ps command:

heroku ps

Declare app dependencies

Heroku recognizes an app as Node.js by the existence of a package.json file in the root directory. For your own apps, you can create one by running npm init.

The demo app you deployed already has a package.json, and it looks something like this:

{
  "name": "node-js-getting-started",
  "version": "0.1.4",
  ...
  "dependencies": {
    "ejs": "^2.3.1",
    "express": "~4.9.x"
  },
  ...
  "engines": {
    "node": "0.12.2"
  },
}

The package.json file determines both the version of Node.js that will be used to run your application on Heroku, as well as the dependencies that should be installed with your application.

When an app is deployed, Heroku reads this file and installs the appropriate node version together with the dependencies using the npm install command.

Run this command in your local directory to install the dependencies, preparing your system for running the app locally:

npm install

Due to a bug in npm, you may receive an error message on Windows that reads something like Error: ENOENT, stat C:\Users\YOURUSERNAME\AppData\Roaming\npm. If you do, manually create this directory with mkdir C:\Users\YOURUSERNAME\AppData\Roaming\npm and rerun npm install.

Once dependencies are installed, you will be ready to run your app locally.

Run the app locally

Now start your application locally using Foreman, which was installed as part of the Toolbelt:

foreman start web

Just like Heroku, Foreman examines the Procfile to determine what to run. Your app will now be running at localhost:5000. Test that it’s working with curl or a web browser, then Ctrl-C to exit.

Foreman doesn’t just run your app - it also sets “config vars”, something you’ll encounter in a later tutorial.

Push local changes

In this step you’ll learn how to propagate a local change to the application through to Heroku. As an example, you’ll modify the application to add an additional dependency and the code to use it. Modify package.json to include a dependency for cool-ascii-faces:

  "dependencies": {
    "ejs": "^2.3.1",
    "express": "~4.9.x",
    "cool-ascii-faces": "~1.3.x"
  },

Modify index.js so that it requires this module at the start. Also add a new route (/cool) that uses it. Your final code should look like this:

var cool = require('cool-ascii-faces');
var express = require('express');
var app = express();

app.set('port', (process.env.PORT || 5000));

app.use(express.static(__dirname + '/public'));

// views is directory for all template files
app.set('views', __dirname + '/views');
app.set('view engine', 'ejs');

app.get('/', function(request, response) {
  response.render('pages/index')
});

app.get('/cool', function(request, response) {
  response.send(cool());
});

app.listen(app.get('port'), function() {
  console.log('Node app is running on port', app.get('port'));
});

Now test locally:

npm install
foreman start

Visiting your application at http://localhost:5000/cool(, you should see cute faces displayed on each refresh: ( ⚆ _ ⚆ ).

Now deploy. Almost every deploy to Heroku follows this same pattern. First, add the modified files to the local git repository:

git add .

Now commit the changes to the repository:

git commit -m "My cool new Node.js app running on Heroku!"

Now deploy, just as you did previously:

git push heroku master

Finally, check that everything is working:

heroku open

Navigate to the /cool route, and you should see another face.

Provision add-ons

Add-ons are third-party cloud services that provide out-of-the-box additional services for your application, from persistence through logging to monitoring and more.

By default, Heroku stores 1500 lines of logs from your application. However, it makes the full log stream available as a service - and several add-on providers have written logging services that provide things such as log persistence, search, and email and SMS alerts when certain conditions are met.

Provision the papertrail logging add-on:

heroku addons:create papertrail

The add-on is now deployed and configured for your application. You can list add-ons for your app like so:

heroku addons

To see this particular add-on in action, visit your application’s Heroku URL a few times. Each visit will generate more log messages, which should now get routed to the papertrail add-on. Visit the papertrail console to see the log messages:

heroku addons:open papertrail

A console will open up, showing the latest log events, and providing you with an interface to search and set up alerts.

Start a console

You can run a command, typically scripts and applications that are part of your app, in a one-off dyno using the heroku run command. It can also be used to launch a REPL process attached to your local terminal for experimenting in your app’s environment:

$ heroku run node
Running `node` attached to terminal... up, run.2132
Detected 512 MB available memory, 512 MB limit per process (WEB_MEMORY)
Recommending WEB_CONCURRENCY=1
>

If you receive an error, Error connecting to process, then you may need to configure your firewall.

When the console starts, it has nothing loaded other than the Node.js standard library. From here you can require some of your application files.

For example, you will be be able to run the following:

> var cool = require('cool-ascii-faces')
> cool()
( ⚆ _ ⚆ )

To get a real feel for how dynos work, you can create another one-off dyno and run the bash command, which opens up a shell on that dyno. You can then execute commands there. Each dyno has its own ephemeral filespace, populated with your app and its dependencies - once the command completes (in this case, bash), the dyno is removed.

$ heroku run bash
Running `bash` attached to terminal... up, run.3052
~ $ ls
Procfile  README.md  composer.json  composer.lock  vendor  views  web
~ $ exit
exit

Don’t forget to type exit to exit the shell and terminate the dyno.

Define config vars

Heroku lets you externalise configuration - storing data such as encryption keys or external resource addresses in config vars.

At runtime, config vars are exposed as environment variables to the application. For example, modify index.js so that the method repeats an action depending on the value of the TIMES environment variable:

app.get('/', function(request, response) {
  var result = ''
  var times = process.env.TIMES || 5
  for (i=0; i < times; i++)
    result += cool();
  response.send(result);
});

Foreman will automatically set up the environment based on the contents of the .env file in your local directory. Create a .env file that has the following contents:

TIMES=2

If you run the app with foreman start, you’ll see two faces will be generated every time. To set the config var on Heroku, execute the following:

heroku config:set TIMES=2

View the config vars that are set using heroku config:

heroku config

Deploy your changed application to Heroku to see this in action.

Provision a database

The add-on marketplace has a large number of data stores, from Redis and MongoDB providers, to Postgres and MySQL. In this step you will add a free Heroku Postgres Starter Tier dev database to your app.

Add the database:

heroku addons:create heroku-postgresql:hobby-dev

This creates a database, and sets a DATABASE_URL environment variable (you can check by running heroku config).

Edit your package.json file to add the pg npm module to your dependencies:

"dependencies": {
    "pg": "4.x",
    "ejs": "^2.3.1",
    "express": "~4.9.x",
    "cool-ascii-faces": "~1.3.x"
}

Type npm install to install the new module for running your app locally. Now edit your index.js file to use this module to connect to the database specified in your DATABASE_URL environment variable:

var pg = require('pg');

app.get('/db', function (request, response) {
  pg.connect(process.env.DATABASE_URL, function(err, client, done) {
    client.query('SELECT * FROM test_table', function(err, result) {
      done();
      if (err)
       { console.error(err); response.send("Error " + err); }
      else
       { response.render('pages/db', {results: result.rows} ); }
    });
  });
})

This ensures that when you access your app using the /db route, it will return all rows in the test_table table.

Deploy this to Heroku. If you access /db you will receive an error as there is no table in the database. Assuming that you have Postgres installed locally, use the heroku pg:psql command to connect to the remote database, create a table and insert a row:

$ heroku pg:psql
psql (9.3.2, server 9.3.3)
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
Type "help" for help.
=> create table test_table (id integer, name text);
CREATE TABLE
=> insert into test_table values (1, 'hello database');
INSERT 0 1
=> \q

Now when you access your app’s /db route, you will see something like this:

                                Database Results
                              * 1 - hello database

Read more about Heroku PostgreSQL. A similar technique can be used to install MongoDB or Redis add-ons.

Next steps

You now know how to deploy an app, change its configuration, view logs, scale, and attach add-ons.

Here’s some recommended reading. The first, an article, will give you a firmer understanding of the basics. The second is a pointer to the main Node.js category here on Dev Center:

*Read How Heroku Works for a technical overview of the concepts you’ll encounter while writing, configuring, deploying and running applications.

*Read Deploying Node.js Apps on Heroku to understand how to take an existing Node.js app and deploy it to Heroku.

*Visit the Node.js category to learn more about developing and deploying Node.js applications.

Documentation

For more information about using Node.js on Heroku, see these Dev Center articles:

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