Ruby on Rails Hello World

Daniel Weibel
Created 21 Apr 2014

Steps for installing and setting up Ruby on Rails, generating an example Ruby on Rails app, and putting it in production mode on Heroku. The assumed operating system is Mac OS X (tested on OS X 10.9.1).

Some of the following steps wouldn’t be really necessary for such a simple hello world app, however, the aim is to show all the basic important steps for creating and deploying serious apps.

Check Which Ruby Version To Use

Check the recommended Ruby version for the current Ruby on Rails release.

Install Required Ruby Version With rbenv

Install rbenv:

brew install rbenv ruby-build

Add the following to ~/.bash_profile and restart shell:

if which rbenv >/dev/null; then eval "$(rbenv init -)"; fi

List available Ruby versions:

rbenv install -l

Install desired Ruby version and set as global default:

rbenv install 2.2.3
rbenv global 2.2.3

Note: if the installation aborts with an error “dtrace: failed to compile script probes.d: Preprocessor not found”, try to install with:

CONFIGURE_OPTS="--disable-dtrace" rbenv install 2.1.0

Install Bundler and Ruby on Rails

gem install bundler
gem install rails

After this, restart shell.

Install Ruby on Rails Plugin for Vim

If you use Vim for editing Ruby on Rails source files, this is recommended. The rails.vim plugin is here

Install PostgreSQL

Note: if the app uses a database, a database must be installed on the local machine for development mode. Typically used databases are SQLite, MySQL, and PostgreSQL. SQLite is the only one that seems to be installed by default on Mac.

Heroku, the production server, uses PostgreSQL by default. It is advisable to use the same database for development and production. Therefore, if the app is to be deployed to Heroku, it’s recommended to install PostgreSQL on the local machine and use it as the development database.

brew install postgres

PostgreSQL Basics

Start PostgreSQL shell:


Here are some basic PostgreSQL shell commands:

db=# select * from pg_roles;  /* Display all PostgreSQL users and their privileges. In database.yml, the user in development mode must be one of these. */
db=# \list                    /* List all databases */
db=# drop database db_name;   /* Delete a specific database (db_name) */
db=# \c db_name	              /* Connect to a specific database (db_name) */
db=# \dt                      /* List all tables in current database */
db=# \q	                      /* Exit PostgreSQL shell */

Tip: enclose db_name or any other name in double quotes, if syntax errors occur.

Generate a Starter Ruby on Rails App

The RailsApps project provides barebones Rails apps that can be used as a starting point for building own apps. The starter apps can be installed and set up interactively with the Rails Composer from the same project. To generate a starter app with Rails Composer, type:

rails new hello-world -m

Rails Composer asks a couple of questions. Choose (for example):

Build a starter application?	Build a RailsApps example application
Starter apps for Rails 4.1.	rails-devise
Web server for development?	Thin
Web server for production?	Thin
Database used in development?	PostgreSQL
Template engine?			ERB
Continuous testing?		None
Front-end framework?		Bootstrap 3.0
Add support for sending email?	Gmail
Devise modules?			Devise with default modules
Use a form builder gem?		SimpleForm

The following questions are important because we use PostgreSQL as the development database:

Username for PostgreSQL?(leave blank to use the app name)
	Choose your UNIX username. The reason is that PostgreSQL has by default
	a user with all the needed privileges with that name.
Host for PostgreSQL in database.yml? (leave blank to use default socket conn.)	
	Leave blank
Password for PostgreSQL user dw? 
	Choose what you want

Run App in Development Mode

Start server (from within project directory):

rails server

The app is now served at http://localhost:3000/

Stop server with Ctr-C

If the starter app includes a login, the existing users and their credentials are in config/secrets.yml.

Now the app works in development mode. Let’s go over to production mode.

Set Up a Heroku Environment

  • First, create an account on the Heroku website.
  • Install the Heroku Toolbelt from here
  • Create SSH keys
      ssh-keygen -t rsa
  • Add public SSH key to Heroku
      heroku keys:add

Create an App Container on Heroku

heroku create hello-world

Most of the following information of deploying a RailsApps starter app to Heroku is also described here

Precompile Assets

Note: Rails compresses (compiles) CSS and JavaScript files (assets) before sending them to the browser. The below command makes sure that this is done at the time of deployment and not at the time of every single request.

rake assets:precompile

Add the rails_12factor Gem to Production Mode

Note: this seems to be missing from the example app. It makes sure that the assets are rendered correctly by Heroku.

Add the following to the Gemfile:

gem 'rails_12factor', group: :production

Adapt Configuration

All the values in config/secrets.yml must evaluate to meaningful strings. They can be pure strings, or they can be of the form ENV["VARIABLE"], in which case they evaluate to the value of the UNIX environment variable VARIABLE.

Set environment vars on Heroku:

heroku config:set VAR=value

Display all Heroku environment vars:

heroku config

Add Procfile for Heroku

Note: this sets to use the Thin application server on Heroku instead of the less robust WEBrick.

Create file Procfile in root of project directory with content:

web: bundle exec rails server thin -p $PORT -e $RACK_ENV

Make a Git commit

Note: the Git repository has been created by Rails Composer.

Push App to Heroku

Note: this pushes the head of the master branch of the Git repository to Heroku. After every local change, a Git commit is necessary before executing below command again.

git push heroku master

Set Up Database on Heroku

heroku run rake db:migrate
heroku run rake db:seed

Access App in Production Mode

heroku open