node.js: install simple sheduler as a rebootsafe service on ubuntu 16.04

There are many situations, in whioch you want to process a serverside workerscript to process queued tasks. Here is a simple solution to setup a nodejs cron script wich runs as a systemd service on ubuntu.

In this sample we are logging a text every second to the console, the filesystem and to the system d status log.

Prerequisits

Installed node.js, npm

Create your project

create a folder "/var/www/html/sheduler"

Init a npm project

create a package.json with following content

	{
	"name": "sheduler",
	"version": "1.0.0",
	"description": "a simple sheduler",
	"main": "index.js",
	"dependencies": {
	"chai": "^3.5.0",
	"mocha": "^3.0.2",
	"node-cron": "^1.1.1",
	"winston": "^2.2.0"
	},
	"devDependencies": {},
	"scripts": {
	"test": "echo \"Error: no test specified\" && exit 1"
	},
	"keywords": [
	"cron",
	"node"
	],
	"author": "pboethig",
	"license": "MIT",
	"bugs": {
	"url": "https://github.com/pboethig/node-cron/issues"
	},
	"homepage": "https://github.com/pboethig/node-cron#readme"
	}

view raw package.json hosted with ❤ by GitHub

open a terminal and run
$ npm install

Install the sheduler

We want to use node-cron for our sheduler.  Node-cron allows us to trigger a script every second. That is ideal, if you want to build a worker wich runs every second. install follwing script 

	var winston = require('winston');
	var logger = new (winston.Logger)({
	transports:[
	new winston.transports.File({
	level: 'info',
	filename: '/var/www/html/sheduler/all-logs.log',
	handleExceptions: true,
	json: true,
	maxsize: 5242880, //5MB
	maxFiles: 5,
	colorize: false
	}),
	new winston.transports.Console({
	level:'debug',
	handleExceptions:true,
	json: false,
	colorize:true
	})
	],
	exitOnError:false
	});
	module.exports = logger;
	var cron = require('cron');
	var cronJob = cron.job("* * * * * *", function()
	{
	logger.info("test1");
	logger.debug("test2");
	});
	cronJob.start();

view raw index.js hosted with ❤ by GitHub

This simple script creates a logger to log to the filesystem and to console every second. The logfile path is set to /var/www/html/sheduler/all-log.log

Install sheduler as a systemd service

To make our sheduler reboot save we now add the script as a systemd service.

add a file:
/etc/systemd/system/nodecron.service

paste following script in this service unit

	[Unit]
	Description=nodecron service
	After=network.target
	[Service]
	User=root
	ExecStart=/usr/bin/node /var/www/html/sheduler/index.js
	[Install]
	WantedBy=multi-user.target

view raw nodecron.service hosted with ❤ by GitHub

This adds a servicedesfinition with the information, what script to execute.

Test your systemd-service

At last we reload our service units by typing:
$ systemctl --system daemon-reload

Enable your service
$ systemctl enable nodecron

 Start your service
$ systemctl start nodecron


Get status
$ systemctl status nodecron 

 If everything works you will get a status like that:

This tells us, that our logger logs every second a info and a debugmessage.
As you can see, our node.js script gets executed successfully. The service is tunning even, if you reboot the machine.

At the end you will find a logfile with your 2 loggings under:
/var/www/html/sheduler/all-logs.log

Disable your service like that
$ systemctl disable nodecron