Install Node.js and PM2

Published on: 5th Dec 2020

Updated on: 30th Jan 2022

What is Node.js

Node.js is a virtual machine for hosting JavaScript programs. It is powerful such that you can write a simple website in a few lines of code.

Why we need it

You may develop your website using Node.js or develop a script to analyze the web access log, etc.

Here's how you install Node.js

To install Node.js

cd ~

# download the setup script - you may review it before executing this script
curl -sL https://deb.nodesource.com/setup_16.x -o nodesource_setup.sh

sudo bash nodesource_setup.sh
sudo apt install nodejs
sudo apt install build-essential

To check version,
```
node -v 
npm -v
```

To remove Node.js

sudo apt-get purge --auto-remove nodejs

If you install Node.js directly, you will have more work when upgrading it to the latest version. To avoid such a situation, we are going to install n which is a Node.js version manager. To install n, run the following command,

# create a directory for 'n' program.
sudo mkdir -p /usr/local/n
sudo chown -R $(whoami) /usr/local/n

sudo mkdir -p /usr/local/node_modules
sudo chown -R $(whoami) /usr/local/node_modules

# create the necessary directories for 'n' to run
sudo mkdir -p /usr/local/bin /usr/local/lib /usr/local/include /usr/local/share
sudo chown -R $(whoami) /usr/local/bin /usr/local/lib /usr/local/include /usr/local/share

If you are running Nodes.js on any of the Linux variant, you may install n which is a Node.js version manager.
```
# ready to install `n` package
npm install -g n
```
- To view the available Node.js version to install,
```
n --lts
```
- To install the latest long term support (lts) version,
```
n lts
```
- To install a specific version,
```
n 17.4.0
```
If you are running Node.js on Windows, you will have to install nvm. Please following the installation steps in the following page:

https://github.com/coreybutler/nvm-windows

Maintaining Node.js app dependencies

First, you have to set the current location to the same as the package.json of your app.

cd /var/www/app1

To check if there is any outdated packages
```
npm outdated
```
To update the node-cron package (for example) to the latest version, run the following command:
```
npm install node-cron@latest
```

Install PM2

The website hosted in Node.js will not be back online after server reboot. In this case, we need a program to start the website. There are many options to achieve this. For us, we choose pm2 due to its flexibility and easy to configure.

To install PM2
```
npm install pm2@latest -g
```
To install log rotate
```
pm2 install pm2-logrotate
```
Set as startup (in Linux) - run the following command in a NON root context,
```
pm2 startup systemd
```
Then, the following result will appear on the screen. You need to copy the command on the screen and run it accordingly. Please take note that 'tester' is our user ID and you may expect different user ID and path.
```
sudo env PATH=$PATH:/usr/local/bin /usr/local/lib/node_modules/pm2/bin/pm2 startup systemd -u tester --hp /home/tester
```

To add your Node.js website to pm2

# goto the app directory
cd /var/www/app1

# start the Node.js app
pm2 start index.js

# save the configuration
pm2 save

To view the app setting (where 'index' is the app name),
```
pm2 describe index
```

Adding Node.js app to pm2 using ecosystem.config.js file

This can be done easily. First, you have to create a ecosystem.config.js file in the app directory (same as the startup script location which is /var/www/app1 used in our blog post) which has the following contents:

module.exports = {
apps: [
    {
    name: "yourappname",
    script: "./index.js",
    exec_mode: "cluster",
    instances: 2,
    shutdown_with_message: true,
    env: {
        NODE_ENV: "production",
    }
}]};

The above settings
- name - the app name that will be displayed when you run the command of pm2 ls.
- script - it is the script file to be running.
- exec_mode - it can be (1) running your app in fork mode or (2) cluster which runs your app multiple instances with port sharing. Default is fork mode.
- instances - the number of instances to be started by pm2.
- shutdown_with_message - if true, the app will be shutdown with process.send('shutdown') instead of process.kill(pid, SIGINT). With true value, your app may listen to the 'shutdown' app message.
After that, run the following command to add the app to pm2,
```
pm2 start ecosystem.config.js
```
For more information, visit the following page:

https://pm2.keymetrics.io/docs/usage/application-declaration/

References

For Node.js, visit this page: https://nodejs.org/en/
For n, Node.js version manager (for Linux platform), visit this page: https://github.com/tj/n
For nvm (for Windows platform), visit this page: https://github.com/coreybutler/nvm-windows
For pm2, you may find out more information at https://pm2.keymetrics.io/

For how to allow public to access your Node.js website, please refers to Install Nginx

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Author

Lau Hon Wan, software developer.