Cluster vs reverse proxy decision in Node.js - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a cluster that forks worker processes.

Node.js

const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  for (let i = 0; i < [1]; i++) {
    cluster.fork();
  }
} else {
  http.createServer((req, res) => {
    res.writeHead(200);
    res.end('Hello from worker ' + process.pid);
  }).listen(8000);
}

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

Aprocess

Bcluster

Chttp

DnumCPUs

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'cluster' or 'http' instead of the CPU count variable.

The code uses numCPUs to fork a worker for each CPU core.

2fill in blank

medium

Complete the code to set up a simple reverse proxy using the 'http-proxy' library.

Node.js

const http = require('http');
const httpProxy = require('http-proxy');

const proxy = httpProxy.createProxyServer({});

const server = http.createServer((req, res) => {
  proxy.web(req, res, { target: [1] });
});

server.listen(8000);

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

A'http://localhost:8000'

B'https://example.com'

C'http://localhost:3000'

D'http://127.0.0.1:8080'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same port as the proxy server or an unrelated URL.

The proxy target is usually a backend server, here running on port 3000 locally.

3fill in blank

hard

Fix the error in the cluster code to properly listen on a port in each worker.

Node.js

const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
} else {
  http.createServer((req, res) => {
    res.writeHead(200);
    res.end('Worker ' + process.pid);
  }).listen([1]);
}

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

A'8000'

B8000

Cprocess.pid

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using process.pid or a string instead of a number for the port.

The server must listen on a numeric port like 8000, not a string or other value.

4fill in blank

hard

Fill both blanks to create a cluster that logs when a worker exits and forks a new one.

Node.js

const cluster = require('cluster');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  for (let i = 0; i < [1]; i++) {
    cluster.fork();
  }

  cluster.on('[2]', (worker, code, signal) => {
    console.log(`Worker ${worker.process.pid} died`);
    cluster.fork();
  });
}

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

AnumCPUs

Bexit

Cdisconnect

Donline

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong event names like 'disconnect' or 'online' for worker death.

The cluster forks workers equal to numCPUs and listens for the 'exit' event to restart workers.

5fill in blank

hard

Fill all three blanks to create a reverse proxy that logs requests and forwards them to a backend.

Node.js

const http = require('http');
const httpProxy = require('http-proxy');

const proxy = httpProxy.createProxyServer({});

const server = http.createServer((req, res) => {
  console.log('Request URL:', [1]);
  proxy.web(req, res, { target: [2] });
});

server.listen([3]);

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

Areq.url

B'http://localhost:4000'

C8080

Dreq.headers

Attempts:

3 left

💡 Hint

Common Mistakes

Logging headers instead of URL, wrong target URL, or wrong listen port.

The code logs the request URL, proxies to the backend at port 4000, and listens on port 8080.