Starter Ruby Application

This document walks through creating a hello world application in Ruby with the Sinatra web framework.

config.ru for Sinatra

The first thing we need for OnDemand to recognize this directory is a config.ru file. For Sinatra this is the config.ru that you need.

# frozen_string_literal: true

require_relative 'app'
run App

config.ru for Ruby on Rails

This document does not cover Ruby on Rails, but this config.ru is given nonetheless for readers interested in building Ruby apps based on Ruby on Rails.

# frozen_string_literal: true

require_relative 'config/environment'

run Rails.application
Rails.application.load_server

Install dependencies

The application won’t boot with just the config.ru, though it will try. What you need now is to install the gems (the ruby dependencies).

We need a Gemfile to tell bundler (Ruby’s application for dependencies) what gems to install. Here’s that file.

# frozen_string_literal: true

source 'https://rubygems.org'

gem 'sinatra'

With the Gemfile written, we can now install the dependencies into vendor/bundle. Issue these commands to do that.

bundle config path --local vendor/bundle
bundle install

Write the app.rb file

Still, the app will not boot at this point. The config.ru is looking to load the app.rb file which does not exist yet.

The app.rb file that will actually import Sinatra and implement your routes. Here’s the simplest version of this file returning Hello World on the root URL.

require 'sinatra/base'

class App < Sinatra::Base
  get '/' do
    'Hello World'
  end
end

Publish App

Publishing an app requires two steps:

1. Updating the manifest.yml to specify the category and optionally subcategory, which indicates where in the dashboard menu the app appears.

2. Having an administrator checkout a copy of the production version to a directory under /var/www/ood/apps/sys.

Steps:

1. Add category to manifest so the app appears in the Files menu:

   name: Quota
   description: Display quotas
   icon: fa://hdd-o
   +category: Files
   +subcategory: Utilities
   

2. Version these changes. Click Shell button on app details view, and then commit the changes:

   git add .
   git commit -m "update manifest for production"
   
   # if there is an external remote associated with this, push to that
   git push origin master
   

3. As the admin, sudo copy or git clone this repo to production

   # as sudo on OnDemand host:
   cd /var/www/ood/apps/sys
   git clone /users/PZS0562/efranz/ondemand/dev/quota
   

4. Reload the dashboard.

Fig. 7 Every user can now launch the Quota from the Files menu.

Warning

Accessing this new app for the first time will cause your NGINX server to restart, killing all websocket connections, which means resetting your active web-based OnDemand Shell sessions.