Can't figure out where to initiate CronJob in react app - reactjs

Question

I have a react app, which must perform a weekly task every Monday #7:58 am. The task is setup as a separate function "notification()". And I want to use the 'CRON' package from NPM to call notification() at the appropriate time.
I have CRON wrapped inside of a function like this:
let mondayNotif = () => {
new CronJob('* 58 7 * * 2', function() {
notification()
}, null, true, 'America/Los_Angeles');
};
My question: where should I call the function mondayNotif(), to make sure that the CronJob is initiated correctly? I thought at first it must be on the backend, but the NPM package doesn't seem to support server-side. But if I call mondayNotif() on the client side, will the CronJob still happen if the site is inactive?

Answer 1

From what I know React JS is front end - it runs on client side. You need a server. In this case a node.js based server. Theroetically if nobody opens the website nothing will be fired up in react js. Look up how to schedule cron jobs on node.js
enter link description here

Answer 2

I found my own answer. But first, a few insights on CronJobs that would have helped me:
CronJobs are essentially a third-party function with an embedded clock. Once they are "initiated", you don't have to call them. The third-party calls them remotely, based on the time that you scheduled in the parameters (ie: "30 6 * * 5").
There is some discrepancy in different blogs about the CRON time. For instance some blogs insisted there are 6 time variables, but I found it worked with 5.
CronJobs should be in a separate file from the body of your main code, typically at the top of your folder structure near your "package.json" & "server.js" files.
It seems to be cleanest to setup all of your CronJob utilities directly inside the cronjob.js file. For instance: I used a separate database connection directly in cronjob.js and by-passed the api routes completely.
CronJobs should be initiated exactly once, at the beginning of the app launch. There are a few ways to do this: package.json or server.js are the most obvious choices.
Here is the file structure I ended up using:
-App
--package.json
--server.js
--cronjob.js
--/routes
--/src
--/models
--/public
...And then I imported the cronjob.js into "server.js". This way the cronjob function is initiated one time, when the server.js file is loaded during "dev" or "build".
For reference, here's the raw cronjob.js file (this is for an email notification):
const CronJob = require('cron').CronJob;
const Department = require('./models/department.js');
const template_remind = require('./config/remindEmailTemplate.js');
const SparkPost = require('sparkpost');
const client = new SparkPost('#############################');
const mongoose = require("mongoose");
const MONGODB_URI =
process.env.MONGODB_URI || "mongodb://localhost:27017/app";
mongoose.Promise = Promise;
// -------------------------- MongoDB -----------------------------
// Connect to the Mongo DB
mongoose.connect(MONGODB_URI, { useNewUrlParser: true }, (err, db) => {
if (err) {
console.log("Unable to connect to the mongoDB server. Error:", err);
} else {
console.log("Connection established to", MONGODB_URI);
}
});
const db = mongoose.connection;
// Show any mongoose errors
db.on("error", error => {
console.log("Mongoose Error: ", error);
});
// Once logged in to the db through mongoose, log a success message
db.once("open", () => {
console.log("Mongoose CRON connection successful.");
});
// ------------------------ Business Logic --------------------------
function weekday(notifications) {
Department.find({"active": true, "reminders": notifications, "week": {$lt: 13}}).distinct('participants', function(err, doc) {
if(err){
// console.log("The error: "+err)
} else {
console.log("received from database... "+JSON.stringify(doc))
for(let i=0; i<doc.length; i++){
client.transmissions.send({
recipients: [{address: doc[i]}],
content: {
from: 'name#sparkmail.email.com',
subject: 'Your email notification',
html: template_remind()
},
options: {sandbox: false}
}).then(data => {})
}
}
})
}
function weeklyNotif() {
new CronJob('45 7 * * 1', function() {weekday(1)}, null, true, 'America/New_York');
new CronJob('25 15 * * 3', function() {weekday(2)}, null, true, 'America/New_York');
new CronJob('15 11 * * 5', function() {weekday(3)}, null, true, 'America/New_York');
}
module.exports = weeklyNotif()
As you can see, I setup a unique DB connection and email server connection (separate from my API file), and ran all of the logic inside this one file, and then exported the initiation function.
Here's what appears in server.js:
const cronjob = require("./cronjob.js");
All you have to do here is require the file, and because it is exported as a function, this automatically initiates the cronjob.
Thanks for reading. If you have feedback, please share.

Answer 3

Noway, do call CronJob from client-side, because if there are 100 users, CronJob will be triggered 100 times. You need to have it on Server-Side for sure