Virtual Machines

• Learning Outcomes
• Resources
• Lab
  • Create a Node.js Application
  • Create a Firewall Rule
  • Create a Virtual Machine
  • Install Node.js on the Virtual Machine
  • Deploying a Node.js Application to a Virtual Machine
  • Crash a Node.js Application
  • Use a Daemon Process Manager to Keep a Node.js Application Alive

Learning Outcomes

• distinguish between real and virtual machines
• configure and provision a VM in the public cloud
• deploy a Node.js application to virtual machine
• use a daemon process manager to keep a Node.js application alive

Resources

• Virtualization Explained (video)
• slides
• narated slides (video)

Lab

Video walkthrough of this lab.

Create a Node.js Application

Start the Google Cloud Shell.

In the terminal, use the Express application generator to create an application skeleton:

npx express-generator --view=ejs myapp

Change to the application directory:

cd myapp

Install the dependencies:

npm install

Run the application:

PORT=8080 DEBUG=myapp:* npm start

Preview the application using the web preview button .

Stop the application (CTRL-C).

Open the editor .

Make a visible change to myapp/views/index.ejs and save the changes.

Re-start the application:

PORT=8080 DEBUG=myapp:* npm start

Refresh the application in the browser and confirm the change took effect.

Stop the application (CTRL-C).

Create a Firewall Rule

From the Google Cloud console page, go to “NETWORKING | VPC network | Firewall”. You may be asked to enable the compute engine API. Just go ahead and enable it.

Click on the “CREATE FIREWALL RULE” button.

• For “Name”, enter “allow-http-8080”.
• Leave “Logs” in the “Off” setting.
• Leave “Network” at “default”
• Leave “Priority” at “1000”.
• Leave “Direction of traffic” at “Ingress”.
• Leave “Action on match” at “Allow”.
• For “Targets”, choose “Specified target tags”.
• For “Target tags”, enter “http-server-8080”.
• Leave “Source filter” at “IP ranges”.
• For “Source IP ranges”, enter “0.0.0.0/0”.
• Leave “Second source filter” at “None”.
• Leave “Protocols and ports” at “Specified protocols and ports”.
• Check “tcp” and enter “8080”.

Click on the “CREATE” button.

Create a Virtual Machine

From the Google Cloud console page, go to “COMPUTE | Compute Engine | VM instances”.

Click on the “CREATE INSTANCE” button.

• For “Name”, enter “lab1”.
• For “Region”, choose either the region geographically closest to you (if you are in Vancouver, this would be “us-west1 (Oregon)”) or “northamerica-northeast1 (Montreal)”.
• Leave “Zone” alone.
• For “Machine configuration | Series”, choose “N1”.
• For “Machine configuration | Machine type”, choose “f1-micro”.
• Confirm that “Boot disk” is set to “Debian GNU/Linux 10 (buster)”.
• Click the “Management, security, disks, networking, sole tenancy” link to expand the available options.
• Click on the “Networking” tab.
• For “Network tags”, enter “http-server-8080”.

Click on the “Create” button.

Install Node.js on the Virtual Machine

Back in the Cloud Shell terminal, verify that the new virtual machine instance is running:

(You may be asked to authorize the API call).

gcloud compute instances list

SSH into the new virtual machine:

gcloud compute ssh lab1 --zone YOUR_ZONE_GOES_HERE

(It will proabably generate a SSH key first. You can leave the passphrase blank.)

Install Node.js:

curl -sL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
sudo apt-get install -y nodejs

Log out of the virtual machine (CTRL-D).

Deploying a Node.js Application to a Virtual Machine

Delete the node_modules directory:

rm -r node_modules

Move to the parent directory:

cd ..

Copy the application to the virtual machine:

gcloud compute scp --recurse myapp lab1: --zone YOUR_ZONE_GOES_HERE

SSH back into the new virtual machine:

gcloud compute ssh lab1 --zone YOUR_ZONE_GOES_HERE

Change to the application directory:

cd myapp

Install the dependencies:

npm install

Run the application:

PORT=8080 DEBUG=myapp:* npm start

In a new tab, browse to the application using the external IP address for the virtual machine (http://NNN.NNN.NNN.NNN:8080).

Stop the application (CTRL-C).

Log out of the virtual machine (CTRL-D).

Crash a Node.js Application

In myapp/views/index.ejs add links to the home page as follows:

<p><a href="/">Home</a></p>
<p><a href="/crash">Crash</a></p>

Create myapp/routes/crash.js as follows:

var express = require('express');
var router = express.Router();

function crash() {
    process.exit();
}

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('index', { title: 'Crash!' });
  setTimeout( crash, 4000 );
});

module.exports = router;

In myapp/app.js, require the “crash” router:

var crashRouter = require('./routes/crash');

and configure the app to use the new router:

app.use('/crash', crashRouter);

Re-start the application:

cd myapp
npm install
PORT=8080 DEBUG=myapp:* npm start

Preview the running application in the browser and follow the “Crash” link to “crash” the application. Wait 4 seconds; follow the “Home” link in the page. The page should not load because the application has stopped.

Remove the node_modules directory and copy the modified application to the virtual machine:

rm -r node_modules
cd ..
gcloud compute scp --recurse myapp lab1: --zone YOUR_ZONE_GOES_HERE

SSH back into the virtual machine:

gcloud compute ssh lab1 --zone YOUR_ZONE_GOES_HERE

Change to the application directory:

cd myapp

Run the application:

PORT=8080 DEBUG=myapp:* npm start

In a new tab, browse to the application using the external IP address for the virtual machine (http://NNN.NNN.NNN.NNN:8080). Follow the “Crash” link to “crash” the application. Wait 4 seconds; follow the “Home” link in the page. The page should not load because the application has stopped.

Use a Daemon Process Manager to Keep a Node.js Application Alive

Install the PM2 daemon process manager:

sudo npm install pm2@latest -g

Change to the bin directory of the application:

cd bin

Start the application using the process manager:

PORT=8080 DEBUG=myapp:* pm2 start www

View the logs for the running application:

pm2 logs

Browse to the application using the external IP address for the virtual machine (http://NNN.NNN.NNN.NNN:8080). Follow the “Crash” link to “crash” the application. Watch the log entries and notice how the process manager automatically restarts the application. Follow the “Home” link in the page and observe how it now works correctly.

Stop the logging application (CTRL-C).

Log out of the virtual machine (CTRL-D).