Make scalable Cron jobs in Node js

Learn How to make scalable cron jobs in Nodejs

What is a Cron Job?
A cron job is basically a Linux command used for scheduling tasks to be executed sometime in the future. This is normally used to schedule a job that is executed periodically — for example, to send out a notice every morning or send a unique discount coupon to customers based on a business logic.

Why Node js ?
It is very simple . Node js is lightweight , fast and works like a charm microservices architecture.
Let us see how simple it is to setup .

Dependencies -

npm i --save node-schedule dotenv

Test Function -

const myCronJob = async () => {
try {
console.info("myCronJob Start")
/* perform your async operation *
await asyncOperation(2000)
console.info("myCronJob End")
}
catch (err) {console.error(`Func.cronJobFunc: ${err}`);}
}

Let us make a mock function which will perform the async operation -

const asyncOperation = (ms)=> new Promise(resolve => setTimeout(resolve, ms));

Cron Expression -

1. A cron expression is a string consisting of six or seven subexpressions (fields) that describe individual details of the schedule .

<minute> <hour> <day-of-month> <month> <day-of-week> <command>

2. Let us schedule our batch job at a specific time everyday.

import { scheduleJob } from “node-schedule”;
scheduleJob(‘0 8 * * *’, () => myCronJob);

3. Here the cron expression is 0 8 * * * which means every day at 8am.

4. You can also make the cron expression configurable by adding a config variable in the .env file , for this case MY_CRON_EXP=0 8 * * * .

import { scheduleJob } from “node-schedule”;
require(“dotenv”).config();
scheduleJob(process.env.MY_CRON_EXP, () => myCronJob);

Note : Make sure to point to the path where you are calling scheduleJob ,
this way the server always listens to your batch job and executes whenever the cron expression is true.

Start Script -

node server.js

Output -

myCronJob Start
myCronJob End

That’s it ! It was that simple this solution can be used to make robust batch jobs by calling databases, implementing a business logic or sending dynamic emails to clients . Every task can be automated !

Thanks for the read . Feel free to ask any questions☺