Zero-downtime deployment concept in Express - Mini Project: Build & Apply

Zero-downtime Deployment Concept with Express

📖 Scenario: You are building a simple Express server that serves a message. You want to prepare your code to support zero-downtime deployment, which means the server can restart without dropping any requests.

🎯 Goal: Build a basic Express server with a simple route. Then add a configuration variable to simulate a graceful shutdown delay. Finally, implement the logic to handle server shutdown gracefully to avoid downtime.

📋 What You'll Learn

Create an Express app with a GET route at '/' that returns 'Server is running'.

Add a variable called shutdownDelay set to 3000 (milliseconds).

Implement a function gracefulShutdown that closes the server after the delay.

Use process.on('SIGTERM') to trigger gracefulShutdown on termination signal.

💡 Why This Matters

🌍 Real World

Zero-downtime deployment is important for web servers to update or restart without interrupting user requests. This project shows how to prepare an Express server to close gracefully when the system signals it to stop.

💼 Career

Many backend developer roles require knowledge of server lifecycle management and deployment strategies. Understanding graceful shutdowns helps maintain reliable services in production.

1

Set up Express server with a GET route

Create an Express app by requiring express and calling it. Then create a server that listens on port 3000. Add a GET route at '/' that sends the text 'Server is running' as the response.

Express

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

// Your code here

Need a hint?

Use require('express') to import Express. Use app.get to create the route. Use app.listen(3000) to start the server.

2

Add shutdown delay configuration

Add a variable called shutdownDelay and set it to 3000 to represent milliseconds delay before shutdown.

Express

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

app.get('/', (req, res) => {
  res.send('Server is running');
});

const server = app.listen(3000);

// Your code here

Need a hint?

Declare const shutdownDelay = 3000; below the server start.

3

Implement graceful shutdown function

Write a function called gracefulShutdown that logs 'Shutdown initiated', waits for shutdownDelay milliseconds using setTimeout, then closes the server and logs 'Server closed'.

Express

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

app.get('/', (req, res) => {
  res.send('Server is running');
});

const server = app.listen(3000);

const shutdownDelay = 3000;

// Your code here

Need a hint?

Use setTimeout with shutdownDelay to delay closing the server.

4

Trigger graceful shutdown on SIGTERM signal

Add a listener for the 'SIGTERM' event on process that calls the gracefulShutdown function.

Express

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

app.get('/', (req, res) => {
  res.send('Server is running');
});

const server = app.listen(3000);

const shutdownDelay = 3000;

function gracefulShutdown() {
  console.log('Shutdown initiated');
  setTimeout(() => {
    server.close(() => {
      console.log('Server closed');
    });
  }, shutdownDelay);
}

// Your code here

Need a hint?

Use process.on('SIGTERM', gracefulShutdown); to listen for termination signals.