Schedule A Cron Job In NodeJS Using node-cron

This tutorial will see how we can Schedule A Cron Job In NodeJS Using the node-cron module.

What is a cron job?

A cron job is the event schedular that runs a job as per the given time interval. So it executes a file linked which is linked to that particular job, it runs the code snippet of it and this configuration is set on the server.
But in NodeJS we can actually set cron job within the application code using the node-cron module.

Installing node-cron and express package

Let us start with creating a new application i.e. a new folder for your project.

# Create a folder
mkdir cron-jobs-node

# Go to a folder
cd cron-jobs-node

# Initialize it, which creates a package.json file that you will use to track dependencies
npm init -y

# Add the express web framework and node-cron module by running the following command
npm install express node-cron

As we have installed the basic required dependencies. Let’s build the server.

Case 1 – Scheduling a task using node-cron

Now, we can build the server and also will use node-cron to schedule a task that will run every minute.
so let’s first create an index.js file

nano index.js

Now, let’s import the required packages and create our scheduler.

// IMPORTING PACKAGES
const express = require('express');
const cron = require('node-cron');
app = express();

// Schedule job to be run on the server.
cron.schedule('* * * * *', () => {
  console.log('running a job every minute');
});

// SERVE THE APP
app.listen(3000);

Now run the server and let’s see what we get in result:

node index.js

# Output
running a job every minute
running a job every minute
running a job every minute
...

You have an example job running every minute. You can stop the server with CTRL+C.

Case 2 – Use node-cron to back up databases

Consider a case where your project needs a backup of the database every day at some timestamp.
This event is basically to prevent any corrupted data which might break the database, so in that case, a backup of a database can be very helpful and it can be less damage for your business.

So let’s assume we have an SQLite DB installed and running on our environment. The Shell command for making a database backup may resemble this:

sqlite3 database.sqlite .dump > data_dump.sql

So there a package available called shelljs which runs the shell command directly from the code.

npm install shelljs --save

Now inside the schedule method, we can run our shell script to dump the database and make a copy of it.

// IMPORTING PACKAGES
const cron = require('node-cron');
const shell = require('shelljs');
const express = require('express');
app = express();

// Backup a database at 11:59 PM every day.
cron.schedule('59 23 * * *', function() {
  console.log('---------------------');
  console.log('Running Cron Job');
  if (shell.exec('sqlite3 database.sqlite .dump > data_dump.sql').code !== 0) {
    shell.exit(1);
  }
  else {
    shell.echo('Database backup complete');
  }
});

// SERVE THE APP
app.listen(3000);

More use case for cronjobs

Similarly, there can be many use cases where we can automate our workflow using the corn job scheduler.
Example such as:

• Send Scheduled Emails
• Maintaining Error Logs
• Cleaning and Maintaining Database
• … etc.

Conclusion

In this article, you learned how to use node-cron to schedule jobs on a Node.js server.
You were introduced to the broader concept of automating repetitive tasks in a consistent and predictable manner. This concept can be applied to your current and future projects.