Building a Time Scheduled Communication Micro-service

In this article, we will build a Node.js application that automatically sends messages to users at a specified time interval.

Prerequisites

To follow along with this article, you need:

Node.js installed on your computer.
Some basic knowledge of working with JavaScript.
A Twilio developer account.

Setting up the application
Configuring Twilio on the application
Sending a message using Twilio API
Automating process flow using node-cron
[Conclusion]

Setting up the application

To get started, proceed to your preferred working directory and then initialize the project with the following command:

npm init -y

The command above will create a package.json file on the project directory with all the default configurations.

In this project, we will need the following dependencies:

dotenv: For loading environmental variables.
node-cron: For running our program on a timely basis.
twilio: For sending messages.
nodemon: For automatically restarting the development server.

Install the dependencies by running the following command:

npm i --save dotenv node-cron twilio
npm i --save-dev nodemon

In the package.json file, modify the scripts object to include the following properties:

"scripts": {
    "start": "node index.js",
    "start:dev": "nodemon index.js"
}

Next, create an index.js file on the root project directory. This file will host all the functionalities that we will implement in the subsequent steps.

Configuring Twilio on the application

To send a message via Twilio API, you need to have your account_sid, auth_token, and Twilio phone number.

In the project folder, create a .env file. The file will host our Twilio credentials or properties.

On the file, add the details below:

TWILIO_ACCOUNT_SID = "your_twilio_account_sid"
TWILIO_AUTH_TOKEN = "your_twilio_auth_token"
TWILIO_PHONE_NUMBER = "your_twilio_phone_no"

To access the above credentials, navigate to your Twilio dashboard, under Project Info, copy the value of ACCOUNT SID and paste it on the file.

Do the same thing for AUTH TOKEN and PHONE NUMBER.

Once you have the credentials set, we are ready for the next step.

Sending a message using Twilio

On the index.js file:

Import the necessary modules, as shown below:

const twilio = require('twilio');
const dotenv = require('dotenv');

Next, load the environmental variables by initializing the config() method from dotenv:

dotenv.config();

Then create a function to send a message:

async function send_message(message){

    // Get the variables
    let accountSid = process.env.TWILIO_ACCOUNT_SID;
    let authToken = process.env.TWILIO_AUTH_TOKEN;
    let senderPhone = process.env.TWILIO_PHONE_NUMBER;

    // Initialize the twilio client
    const client = new twilio(accountSid, authToken);

    // Send a message
    let response = await client.messages.create({
        body: message,
        from: senderPhone,
        to: 'your_phone_number'
    });

    console.log(response);
}

In the above function, we are:

Retrieving our environmental variables.
Initializing the Twilio client.
Sending a message using the Twilio client.

On a trial account, the phone number you put in must be verified by Twilio. You can access your verified phone number list from here.

In case you want to send to a different number than the ones on the list, ensure you add it by clicking the Add new caller ID button on the top right.

In case you want to send to more than one party, use an array and separate the phone numbers with a comma as follows:

['phone_number_1','phone_number_2']

Below the send_message function, add the following code to send a hello message:

send_message("Hello there");

We can now run our application using the command below:

npm run dev

Once the function runs, you should receive a hello there message on the phone number that you set.

In the next step, we will automate the process (sending messages) on a timely basis.

Automating process flow using node-cron

Automating the process flow on a timely basis involves sending a message after a specific period. For example: after every hour, minute, second, or even day.

We will implement this functionality using the following steps:

Import the node_cron module:

const node_cron = require('node-cron');

Write a scheduler to call the function after every five minutes:

node_cron.schedule('*/5 * * * *', () => {
    // Run the function after every five minutes.
    console.log("Running after every five minutes");
    send_message('Hello There!'); 
});

Ensure that the send_message('Hello there!') function is still running. If it is not, you will need to call the method as demonstrated in the previous step.

You should now receive a Hello There! message every five minutes.