Handling worker crashes and restart in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a worker thread in Node.js.

Node.js

const { Worker } = require('worker_threads');

const worker = new Worker([1]);

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

A'worker.js'

B'./worker.js'

C'./worker'

D'worker'

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting './' in the path string

Using a path without quotes

Passing a directory instead of a file

The Worker constructor requires the path to the worker script as a string with './' prefix to indicate a relative path.

2fill in blank

medium

Complete the code to listen for the 'exit' event on the worker.

Node.js

worker.on('[1]', (code) => {
  console.log(`Worker exited with code ${code}`);
});

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Aend

Bclose

Cfinish

Dexit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'close' or 'end' which are not valid worker events

Misspelling the event name

The 'exit' event is emitted when a worker thread stops running.

3fill in blank

hard

Fix the error in the code to restart the worker after it crashes.

Node.js

worker.on('exit', (code) => {
  if (code !== 0) {
    [1] = new Worker('./worker.js');
  }
});

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Aworker

BWorker

CnewWorker

DworkerThread

Attempts:

3 left

💡 Hint

Common Mistakes

Using a new variable name without updating references

Using the class name 'Worker' instead of the variable

We must assign the new Worker instance back to the existing 'worker' variable to replace the crashed worker.

4fill in blank

hard

Fill both blanks to listen for errors and restart the worker safely.

Node.js

worker.on('[1]', (err) => {
  console.error('Worker error:', err);
  worker.[2]();
  worker = new Worker('./worker.js');
});

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Aerror

Bexit

Cterminate

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'exit' event instead of 'error' for error handling

Calling a non-existent method instead of 'terminate()'

The 'error' event catches worker errors. Calling 'terminate()' stops the worker before restarting.

5fill in blank

hard

Fill all three blanks to send a message to the worker, listen for messages, and handle worker exit.

Node.js

worker.[1]({ task: 'start' });

worker.on('[2]', (msg) => {
  console.log('Message from worker:', msg);
});

worker.on('[3]', (code) => {
  if (code !== 0) {
    console.log('Restarting worker...');
    worker = new Worker('./worker.js');
  }
});

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

ApostMessage

Bmessage

Cexit

Dsend

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send' instead of 'postMessage' to send data

Listening for wrong event names

Not handling worker exit properly

Use 'postMessage' (A) to send messages to the worker, listen for the 'message' event (B), and handle the 'exit' event (C).