Why logging matters in production in Express - See It in Action

Why logging matters in production

📖 Scenario: You are building a simple Express server that handles user requests. In real life, servers need to keep track of what happens during their operation. This is called logging. Logging helps developers understand what the server is doing, find problems, and improve the system.

🎯 Goal: Learn how to add basic logging to an Express server to record important events like incoming requests and errors. This will help you see why logging is important in production environments.

📋 What You'll Learn

Create an Express server with a basic route

Add a configuration variable to control logging level

Implement logging of requests and errors based on the logging level

Print the logs to the console

💡 Why This Matters

🌍 Real World

In real production servers, logging is essential to monitor server health, debug issues, and understand user activity.

💼 Career

Knowing how to add and manage logging is a key skill for backend developers and DevOps engineers to maintain reliable applications.

1

Set up a basic Express server

Create an Express server by importing express, then create an app with express(). Add a GET route at '/' that sends the text 'Hello World'. Finally, make the app listen on port 3000.

Express

const express = require('express');
const app = express();

// Your code here

Need a hint?

Use express() to create the app. Use app.get for the route. Use app.listen(3000) to start the server.

2

Add a logging level configuration

Create a variable called LOG_LEVEL and set it to the string 'info'. This variable will control how much logging the server does.

Express

const express = require('express');
const app = express();

const LOG_LEVEL = 'info';

// Your code here

Need a hint?

Just create a constant LOG_LEVEL and assign it the string 'info'.

3

Add logging for incoming requests

Use app.use to add a middleware function that logs the HTTP method and URL of every incoming request, but only if LOG_LEVEL is set to 'info'. Use console.log to print the message Received [METHOD] request for [URL].

Express

const express = require('express');
const app = express();

const LOG_LEVEL = 'info';

app.use((req, res, next) => {
  // Your code here
});

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

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

Need a hint?

Use app.use to add middleware. Inside it, check if LOG_LEVEL is 'info'. If yes, log the method and URL. Call next() to continue.

4

Log errors and print logs

Add an error-handling middleware using app.use with four parameters: err, req, res, next. Inside it, use console.error to log the error message only if LOG_LEVEL is 'info'. Then send a 500 status with the text 'Server error'. Finally, print 'Logging complete' to the console.

Express

const express = require('express');
const app = express();

const LOG_LEVEL = 'info';

app.use((req, res, next) => {
  if (LOG_LEVEL === 'info') {
    console.log(`Received ${req.method} request for ${req.url}`);
  }
  next();
});

// Your code here

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

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

Need a hint?

Add error middleware with four parameters. Log errors with console.error if LOG_LEVEL is 'info'. Send 500 status and message. Print 'Logging complete' after server starts.