Introduction to Kue Scheduler

Kue-scheduler is a powerful and flexible job scheduling tool for Node.js, built on top of Kue. It allows developers to create, schedule, and manage jobs with ease. This guide will provide an in-depth look at kue-scheduler, explaining its APIs with coding examples to help you understand how to integrate it into your applications.

Installation

 npm install kue-scheduler --save

Creating a Kue Scheduler Instance

 const kue = require('kue');
 const Queue = require('kue-scheduler');
 const queue = Queue.createQueue();

Scheduling Jobs

Scheduling a job with kue-scheduler is straightforward. Here are some examples:

Scheduling a Job to Run Once at a Specific Time

 const job = queue.createJob('myJobType', { title: 'my job' });
 queue.schedule('at 03:30pm', job);

Scheduling a Recuring Job

 queue.every('5 minutes', 'myRecurringJob', { title: 'my recurring job' });

Scheduling with a Crontab Syntax

 queue.schedule('0 15 * * *', 'myCrontabJob', { title: 'my crontab job' });

Managing Scheduled Jobs

kue-scheduler provides several methods to manage jobs:

Checking if a Job is Scheduled

 queue.scheduled('every 5 minutes', 'myRecurringJob', (err, isScheduled) => {
   if (isScheduled) {
     console.log('The job is scheduled');
   }
 });

Removing a Scheduled Job

 queue.remove('every 5 minutes', 'myRecurringJob', (err) => {
   if (!err) {
     console.log('The job has been removed');
   }
 });

Using kue-scheduler in an Application

Below is an example of a simple Node.js application that uses kue-scheduler to handle job scheduling:

 const express = require('express');
 const kue = require('kue');
 const Queue = require('kue-scheduler');
 const queue = Queue.createQueue();

 const app = express();

 const jobType = 'email';

 // Job processing logic
 queue.process(jobType, (job, done) => {
   sendEmail(job.data, done);
 });

 // Function to send an email (dummy function)
 function sendEmail(data, done) {
   console.log('Sending email to:', data.email);
   setTimeout(() => {
     done();
   }, 1000);
 }

 // API to schedule an email job
 app.post('/schedule-email', (req, res) => {
   const email = req.body.email;
   const job = queue.createJob(jobType, { email });
   queue.schedule('at 10:00am', job);
   res.send('Email job scheduled');
 });

 app.listen(3000, () => {
   console.log('Server is running on port 3000');
 });

This application sets up an Express server with an endpoint to schedule jobs. When a POST request is made to /schedule-email with an email address, it schedules an email job to be sent at 10:00am. The job is processed by the queue.process method, which simulates sending an email.

Conclusion

kue-scheduler is a robust solution for job scheduling in Node.js. It seamlessly integrates with Kue and provides a range of APIs to create and manage jobs. By leveraging these features, you can build efficient job scheduling systems tailor-made for your application’s needs.

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