How to restart Node.js application when uncaught exception happen ?

In this article, we are going to learn, about restarting a Node.js application when an uncaught exception happens. For this, we are going to use the pm2 module.

Approach: Let's see the approach step by step:

• Step 1: Install the pm2 module and use it to start the server.
• Step 2: When an uncaught exception happens, then execute the command process.exit() to stop the server.
• Step 3: Then, pm2 module will automatically start the server again.

process.exit() stop the server and pm2 force it to start. In this way, the server will restart.

Implementation: Below is the step-by-step implementation of the above approach.

Step 1: Initializes NPM: Create and Locate your project folder in the terminal & type the command

npm init -y

It initializes our node application & makes a package.json file.

Step 2: Install Dependencies: Locate your root project directory into the terminal and type the command

npm install express pm2

To install express and pm2 as dependencies inside your project

Step 3: Creating a list of products: Let's create an array of products and set it to constant products.

const products = [];

Step 4: Creating Routes for the home page and the products page: Let's create two routes so that users can access the home page and the products page.

app.get('/', (req, res) => {
   res.send('Hello Geeks!');
});

app.get('/products', (req, res) => {
   if (products.length === 0) {
       res.send('No products found!');
       process.exit();
   } else {
       res.json(products);
   }
});

Inside the product route, we use process.exit() method to stop the server.

Complete Code:

const express = require('express');
const app = express();
const products = [];

app.get('/', (req, res) => {
    res.send('Hello Geeks!');
});

app.get('/products', (req, res) => {
    if (products.length === 0) {
        res.send('No products found!');
        process.exit();
    } else {
        res.json(products);
    }
});


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

Steps to run the application: Inside the terminal type the command to run your script 'app.js' with pm2.

pm2 start app.js

Output: