Zero-downtime deployment concept in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an Express server that listens on port 3000.

Express

const express = require('express');
const app = express();
app.get('/', (req, res) => res.send('Hello World!'));
app.listen([1], () => console.log('Server running'));

Drag options to blanks, or click blank then click option'

A3000

B80

C5000

D8080

Attempts:

3 left

💡 Hint

Common Mistakes

Using port 80 without permissions

Using an undefined port variable

The server listens on port 3000, which is a common default for Express apps.

2fill in blank

medium

Complete the code to gracefully close the server on shutdown.

Express

const server = app.listen(3000);
process.on('SIGTERM', () => {
  server.[1](() => {
    console.log('Server closed');
  });
});

Drag options to blanks, or click blank then click option'

Aclose

Bstop

Cshutdown

Dend

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like stop or shutdown

Calling end which is for streams

The close method stops the server from accepting new connections and waits for existing connections to finish.

3fill in blank

hard

Fix the error in the code to handle new connections during zero-downtime deployment.

Express

const http = require('http');
const server = http.createServer(app);
server.listen(3000);
server.on('connection', (socket) => {
  socket.[1] = false;
});

Drag options to blanks, or click blank then click option'

Aclose

Bdestroy

Cclosed

Ddestroyed

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods instead of properties

Confusing 'close' event with property

The destroyed property indicates if the socket is destroyed. Setting it to false means the socket is active.

4fill in blank

hard

Fill both blanks to track active connections and close them on shutdown.

Express

const connections = new Set();
server.on('connection', (socket) => {
  connections.[1](socket);
  socket.on('close', () => connections.[2](socket));
});

Drag options to blanks, or click blank then click option'

Aadd

Bremove

Cdelete

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'push' on a Set

Using 'remove' which is not a Set method

Use add to add sockets to the set and delete to remove them when closed.

5fill in blank

hard

Fill all three blanks to close all active connections during server shutdown.

Express

process.on('SIGTERM', () => {
  server.[1](() => console.log('Server closed'));
  for (const socket of connections) {
    socket.[2]();
    connections.[3](socket);
  }
});

Drag options to blanks, or click blank then click option'

Aclose

Bdestroy

Cdelete

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'stop' which does not exist

Using 'close' on sockets instead of 'destroy'

Call close on the server, destroy on each socket to close it, and delete to remove the socket from the set.