Implementing Pino Logger in Node.js and ExpressJS: A Comprehensive Guide

Logging is an essential part of any application, offering critical insights into the system's behavior, aiding in debugging, and monitoring performance. In the Node.js ecosystem, Pino stands out as a fast, low-overhead logging library. In this guide, we will explore how to implement Pino logger in a Node.js and ExpressJS application.

Why Pino?

Pino is favored for several reasons:

• Performance: It is designed to be extremely fast, with minimal overhead.

• Structured Logs: Logs are output in JSON format, making them easy to parse and analyze.

• Ecosystem: Pino offers a rich ecosystem of plugins and integrations.

Setting Up Your Node.js and Express Project

Before we start, ensure you have Node.js and npm installed. Create a new Node.js project and set up ExpressJS:

mkdir express-pino-logger
cd express-pino-logger
npm init -y
npm install express

Installing Pino and Related Packages

Next, install Pino and its HTTP logging middleware for Express:

npm install pino pino-http

Optionally, you can install pino-pretty for better log readability during development:

npm install pino-pretty --save-dev

Configuring Pino in Your Express Application

1. Create a Logger Configuration File

   Start by creating a logger.js file to configure Pino:

    const pino = require('pino');
   
    const logger = pino({
      level: process.env.NODE_ENV !== 'production' ? 'debug' : 'info',
      transport: process.env.NODE_ENV !== 'production' ? {
        target: 'pino-pretty',
        options: {
          colorize: true
        }
      } : undefined
    });
   
    module.exports = logger;
   

2. Integrate Pino HTTP Middleware

   Next, set up the Pino HTTP middleware in your Express application. Modify your app.js (or index.js if you are using that as your main file):

    const express = require('express');
    const pino = require('pino-http');
    const logger = require('./logger');
   
    const app = express();
   
    // Use Pino HTTP middleware
    app.use(pino({ logger }));
   
    app.get('/', (req, res) => {
      req.log.info('Root route accessed');
      res.send('Hello World!');
    });
   
    const port = 3000;
    app.listen(port, () => {
      logger.info(`Server is running on port ${port}`);
    });
   

Using Pino Logger in Your Application

With Pino integrated, you can now use the logger within your application routes and middleware.

Logging Requests and Responses

Pino HTTP middleware logs incoming requests and outgoing responses automatically. The logs include details such as HTTP method, URL, status code, and response time.

Custom Logging

You can log custom messages within your routes and middleware using req.log. For example:

app.get('/custom', (req, res) => {
  req.log.info('Custom route accessed');
  res.send('This is a custom route');
});

Pretty-Printing Logs in Development

To enhance log readability during development, ensure the transport option is set up correctly in the logger.js file. The pino-pretty transport formats the logs for better readability:

const logger = pino({
  level: process.env.NODE_ENV !== 'production' ? 'debug' : 'info',
  transport: process.env.NODE_ENV !== 'production' ? {
    target: 'pino-pretty',
    options: {
      colorize: true
    }
  } : undefined
});

Conclusion

Integrating Pino logger into a Node.js and ExpressJS application significantly enhances logging capabilities while maintaining performance. Pino's structured logging and extensive feature set make it an excellent choice for modern web applications. By following this guide, you can set up and start using Pino in your ExpressJS projects, ensuring efficient and structured logging.

Happy coding!