SystemD with NodeJS

I want to run a nodeJS application via SystemD.   These will be my simple notes on how to do this.

Simple Node Express app

First let me create a simple Node Express Server.

> mkdir node-systemd   > cd node-systemd

> vi package.json

And put the following in it.

{   "name": "node-systemd",   "version": "0.1.0",   "description": "Simple Node Express app to run via systemd",   "main": "app.js",   "private": true,   "author": "Patrick Bailey",   "dependencies": {     "express": "^4.15.2"   } }

Now create the app.js

> vi app.js

var express = require('express'); const app = express() app.get('/', function (req, res) {   res.send('Hello World!')   console.log("Hello World") }) app.get('/kill', function (req, res) {   res.send('killing app!')   console.log("Shutting down application")   process.exit() }) app.listen(3000, function () {   console.log('Example app listening on port 3000!') })

Now run npm

> npm install   > nodejs app.js

Now run a simple curl

> curl localhost:3000

Now curl the /kill url

> curl localhost:3000

That should kill the app

And it did.

I wanted to add this so that I can easily test that systemd will restart the app if it is shut down.

SystemD

Let me move my node-system app to /opt on my server

> sudo mv node-systemd /opt

Then create a nodejs user/group to use to run the nodejs app.   (It will not have a default shell)

> sudo addgroup nodejs   > sudo adduser --system --ingroup nodejs \      --no-create-home nodejs

 

Now change ownership of all the node-systemd files to nodejs:nodejs

> sudo chown -R nodejs:nodejs /opt/node-systemd

Now create a systemd script

> sudo vi /lib/systemd/system/nodejs.service

And place the following in it

[Unit] Description=NodeJS Express Server Requires=network.target After=network.target ConditionPathExists=/opt/node-systemd/app.js [Service] Type=simple PIDFile=/var/run/nodejs.pid User=nodejs Group=nodejs WorkingDirectory=/ opt/node-systemd ExecStart=/usr/bin/nodejs app.js Restart=always RestartSec=3 [Install] WantedBy=multi-user.target Alias=nodejs.service

 

Make enable it and start it.  (Enable will cause it to start whenever the server reboots)

> sudo systemctl enable nodejs.service   > sudo systemctl start nodejs

Now try and curl it

> curl localhost:3000

OK that failed I did something wrong…

Query the status of this service

> sudo systemctl status nodejs

Yep something is wrong.

Running it by hand works…

Switching to the nodejs user and running it works.

> sudo su nodejs -s /bin/bash

Oops I see it now.  There is a space after / and before opt in my Working Directory.

Let me fix that

> sudo vi /lib/systemd/system/nodejs.service

And place the following in it

[Unit] Description=NodeJS Express Server Requires=network.target After=network.target ConditionPathExists=/opt/node-systemd/app.js [Service] Type=simple PIDFile=/var/run/nodejs.pid User=nodejs Group=nodejs WorkingDirectory=/opt/node-systemd ExecStart=/usr/bin/nodejs app.js Restart=always RestartSec=3 [Install] WantedBy=multi-user.target Alias=nodejs.service

Now let me start it and check the status

But first I need to reload since the script was altered

> sudo systemctl daemon-reload

> sudo systemctl start nodejs   > sudo systemctl status nodejs

 

Looks better!  Now to test it.

> curl localhost:3000

That worked.

This program is not currently logging to any directory.  But I can use the journalctl like I might use the tail command to see its output.

> sudo journalctl -f -u nodejs

Now if I run a few curls

Now let me use the /kill url to kill it and it should restart itself.

> curl localhost:3000/kill

Boom!   it restarted itself after a failure!

Now to double check it all let me reboot the server and make sure it starts up.

> sudo reboot now

> sudo journalctl -f -u nodejs

And start a few curls

> curl localhost:3000   > curl localhost:3000   > curl localhost:3000/kill

Looks good!

References

NA