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

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Node.js Cluster vs Reverse Proxy

Which statement best explains the main difference between using Node.js cluster module and a reverse proxy like Nginx for handling multiple requests?

A Cluster and reverse proxy both create multiple Node.js processes but differ in how they handle database connections.

B Cluster forwards requests to external servers, while reverse proxy creates multiple Node.js processes internally.

C Cluster creates multiple Node.js processes to use all CPU cores, while reverse proxy forwards requests to one or more servers without creating Node.js processes.

D Cluster is used only for load balancing HTTP requests, reverse proxy is used only for caching static files.

💡 Hint

Think about where the work happens: inside Node.js or outside it.

The cluster module creates multiple Node.js processes to utilize multiple CPU cores, improving concurrency within the same machine. A reverse proxy like Nginx forwards incoming requests to one or more backend servers but does not create Node.js processes itself.

❓ component_behavior

intermediate

Behavior of Node.js Cluster Module

Given the following Node.js cluster code, what will be the output when you run it on a machine with 2 CPU cores?

import cluster from 'cluster';
import os from 'os';

if (cluster.isPrimary) {
  const cpuCount = os.cpus().length;
  for (let i = 0; i < cpuCount; i++) {
    cluster.fork();
  }
  console.log(`Primary process started ${cpuCount} workers.`);
} else {
  console.log(`Worker process ${process.pid} started.`);
}

A

Primary process started 2 workers.
Worker process 1234 started.
Worker process 1235 started.

B

Primary process started 1 worker.
Worker process 1234 started.

C Only one line: Primary process started 2 workers.

D SyntaxError due to missing require statements.

💡 Hint

Remember that cluster.fork() creates a new worker process for each CPU core.

The primary process forks one worker per CPU core. Each worker logs its own start message. So you see one primary message and two worker messages on a 2-core machine.

❓ state_output

advanced

Load Distribution with Reverse Proxy

Consider a reverse proxy setup with Nginx forwarding requests to two Node.js servers running on ports 3000 and 3001. If Nginx uses round-robin load balancing, what will be the sequence of server ports handling 4 consecutive requests?

A 3000, 3000, 3001, 3001

B 3000, 3001, 3000, 3001

C 3001, 3000, 3001, 3000

D All requests handled by 3000

💡 Hint

Round-robin means cycling through servers one by one.

Round-robin load balancing sends each new request to the next server in the list, cycling through them evenly.

📝 Syntax

advanced

Correct Cluster Setup Syntax

Which option correctly sets up a Node.js cluster that logs worker IDs when they start?

Node.js

import cluster from 'cluster';
import os from 'os';

if (cluster.isPrimary) {
  const cpuCount = os.cpus().length;
  for (let i = 0; i < cpuCount; i++) {
    cluster.fork();
  }
} else {
  console.log(`Worker ${cluster.worker.id} started.`);
}

A Add parentheses after cluster.fork like cluster.fork().

B Replace cluster.isPrimary with cluster.isMaster.

C Use cluster.worker.process.id instead of cluster.worker.id.

D Correct as is.

💡 Hint

Check the current Node.js cluster API for primary process detection.

In Node.js 20+, cluster.isPrimary replaces cluster.isMaster. The code uses the correct property and syntax.

🔧 Debug

expert

Debugging Reverse Proxy Connection Issue

You have a reverse proxy (Nginx) forwarding requests to a Node.js server on port 4000. The proxy returns 502 Bad Gateway errors. Which of the following is the most likely cause?

A Node.js server is not running or not listening on port 4000.

B Node.js server is running but has a syntax error in the code.

C Nginx configuration has a syntax error unrelated to upstream settings.

D Client browser cache is outdated.

💡 Hint

502 Bad Gateway means the proxy cannot reach the backend server.

A 502 error usually means the reverse proxy cannot connect to the backend server. If the Node.js server is not running or listening on the expected port, Nginx cannot forward requests.