How to fix Error: Cannot send message on closed message port (worker disconnected) in Node.js

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

const worker = new Worker('./worker.js');

// Track when worker exits
worker.on('exit', (code) => {
  console.log(`Worker exited with code ${code}`);
  // Stop sending messages after this point
});

// Track when worker encounters an error
worker.on('error', (error) => {
  console.error('Worker error:', error);
});

// Track when worker is terminated
worker.on('messageerror', (error) => {
  console.error('Message error:', error);
});

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

const { port1, port2 } = new MessageChannel();
let isPortOpen = true;

port1.on('close', () => {
  isPortOpen = false;
  console.log('Port closed');
});

// Safe message sending
function sendMessage(data) {
  if (isPortOpen) {
    port1.postMessage(data);
  } else {
    console.warn('Cannot send message: port is closed');
  }
}

// main.js
const { Worker } = require('worker_threads');

const worker = new Worker('./worker.js');
let workerActive = true;

worker.on('message', (msg) => {
  if (msg.type === 'DONE') {
    workerActive = false;
    worker.terminate();
  }
});

function sendToWorker(data) {
  if (workerActive) {
    worker.postMessage(data);
  } else {
    console.log('Worker has completed, not sending message');
  }
}

// worker.js
const { parentPort } = require('worker_threads');

parentPort.on('message', (data) => {
  // Process data
});

// Signal completion before exit
parentPort.postMessage({ type: 'DONE' });

function safeSendMessage(worker, message) {
  try {
    worker.postMessage(message);
  } catch (error) {
    if (error.message.includes('closed message port')) {
      console.warn('Worker port is closed, message not sent');
      // Handle the closed port scenario
    } else {
      throw error; // Re-throw unexpected errors
    }
  }
}

class WorkerPool {
  constructor(workerScript, poolSize) {
    this.workers = [];
    this.activeWorkers = new Set();

    for (let i = 0; i < poolSize; i++) {
      const worker = new Worker(workerScript);
      this.workers.push(worker);
      this.activeWorkers.add(worker);

      worker.on('exit', () => {
        this.activeWorkers.delete(worker);
      });
    }
  }

  sendToAvailableWorker(data) {
    const availableWorker = Array.from(this.activeWorkers)[0];

    if (availableWorker) {
      availableWorker.postMessage(data);
      return true;
    } else {
      console.warn('No active workers available');
      return false;
    }
  }

  terminate() {
    this.workers.forEach(w => w.terminate());
    this.activeWorkers.clear();
  }
}