What I intend to do is a program that sends congratulatory emails for their birthday to several users, then the program will take today and execute a query to the database (it is an Excel file), in which it will take the date of the users and compare their date of birth with the current date, if the month and day coincide, mail will be sent. I think it can be done with a setInterval(), but I don't know if it affects the performance of the program. Since it will be uploaded on a windows server 2012 server of my company.

My code:

const express = require("express");
const app = express();
const excel = require('./public/scripts/readExcel.js');
const email = require('./services/email/sendEmail.js');
     
app.post('/send-email',(req, res)=>{
  setInterval(() => {
    email.sendEmail()
    .then((result) => {
        res.status(200).jsonp(req.body);;
        console.log(result)
    }).catch((err) => {
        res.status(500).jsonp(req.body);;
        console.log(err);
    });
  }, 3600000);//1 hour
    
});
app.listen(4000, ()=>{
    console.log("Serven on -> http://localhost:4000");
})

Basically what it does is call the sendEmail function every hour which reads the Excel file or the database and extracts the date fields, compares with the current day, and sends the mail with Nodemailer to those who have birthdays. Also, the setInterval would go in the route of "/send-email" or how would the request be made?

CodePudding user response：

For that, you can also run a cron job at every hour using npm package cron-job using

var cron = require('node-cron');

cron.schedule('* * 1 * *', () => {
  console.log('running a task every hour');
});

CodePudding user response：

I'll break down my answer in two parts

1. What you need to do to make your solution work
2. How can you optimise the performance

1. What you need to do to make your solution work

There are two essential problems you need to resolve.

a. Your solution will work as it is, only thing you need to do is to call /send-email endpoint once after starting your server. BUT... this comes with side effects. As setInterval will call the email.sendEmail... code block every hour, and this code block calls res.status(200).jsonp(req.body) every time. If you don't know this res.status.. sets the response for the request you receive. In this case, your request to /send-email. For the first time, it will work fine because you are returning the response to your above request. But when second time call to this code block kicks in, it has nothing to respond to because request has already been responded. Remember, HTTP protocol responds to a request once, then the request has been completed. So for this reason, your code block res.status... becomes invalid. So first thing, call res.status only once. So I'd remove this line out of the setInterval code block as follows

app.post('/send-email',(req, res)=>{
  setInterval(() => {
    email.sendEmail()
    .then((result) => {
        console.log(result)
    }).catch((err) => {
        console.log(err);
    });
  }, 3600000);//1 hour
  res.status(200).jsonp(req.body);
})

b. Also I don't think you'd want the hastle of calling /send-email every time you start server, so I'd also make sure that this code block for birthday wishes gets kicked off every time you start server automatically. So I'd then just remove the line app.post('/send-email',(req, res)=>{. Also not that I'm not calling this for a request, I don't have any request to send response to so I can also remove the res.status.. line. And your code looks like this now

const express = require("express");
const app = express();
const email = require('./services/email/sendEmail.js');

(function(){ 
  // Birthday wish email functionality
  setInterval(() => {
    email.sendEmail()
    .then((result) => {
        console.log(result)
    }).catch((err) => {
        console.log(err);
    });
  }, 3600000);//1 hour
})() // Immediately invoked function
    

That's it, your solution works now. Now to send birthday wish emails, you don't need to do anything else other than just starting your server.

Let's move on to second part now

2. How can you optimise the performance

a. Set interval to be 24hrs instead of 1 hr

Why do you need to check every hour for birthday? If you don't have a good answer here, I'd definitely change the interval to be 24hrs

b. Making the code more robust to deal with large data

As long as you have only 100s of entries in your excels and they are not going to grow much in future, I wouldn't go into making it more complex for performance. But if your entries are destined to grow to 1000s and further. I'd suggest to use database(such as mongodb, postgres or mysql, etc.) to store your data and query only the entries with the birthday matching the particular date. I'd also implement a queuing system to process query and send emails in batches instead of doing all of that at once.