Starter NodeJS Application

This document describes how to start a Passenger application in NodeJs language.

Initialize the application

In this example we’re going to initialize an application called nodejs-hello-world. You may want to rename this directory to something more appropriate.

cd ~/ondemand/dev
mkdir nodejs-hello-world
cd nodejs-hello-world
npm init

Warning

npm init will initialize the main script as index.js. For OnDemand to recognzie this application, the main attribute in package.json should be app.js not index.js.

Add Web Framework

First we need to add Express web framework. Like all web frameworks, this library will route requests to the appropriate pages.

Issue these commands to add and install the package.

npm add express
npm install

Tip

While this example uses Express, you can choose any NodeJs web framework available.

Add and edit app.js

Now we need the app.js file that’s the entrypoint for this application. After creating this file, we’ve provided this starter content for you add to the file.

This app.js imports the Express framework and sets up the router to route requests to the functions that can serve that request. This starter file only has one route to the root url / and returns a simple Hello World string.

// app.js

const express = require('express');
const app = express();
const port = 3000;

// have to use a Router to mount the `PASSENGER_BASE_URI`
// base uri that's /pun/dev/appname or /pun/sys/appname depending
// on the environment.
const router = express.Router();
app.use(process.env.PASSENGER_BASE_URI || '/', router);

router.get('/', (req, res) => {
  res.send('Hello World!');
})

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
})

Boot the application

Now that the app’s all setup and implemented, you should be able to boot it up. To do so, simply navigate to My Sandbox Apps (Development) in the Develop menu of your OnDemand installation.

There you should see this application at the top of the list. Clicking Launch Nodejs Hello World will launch this application in a new tab.

When the new tab opens you should see a blank page with the text Hello World. This is your new NodeJs application!

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. 8 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.