Node.js berjalan di single thread dengan event loop. Untuk tugas CPU-intensive, gunakan Worker Threads agar tidak memblokir event loop.

Masalah single thread:

// BLOCKING — ini akan memblokir semua request lain!
app.get("/heavy", (req, res) => {
  let result = 0;
  for (let i = 0; i < 10_000_000_000; i++) {
    result += i;
  }
  res.json({ result });
});

Solusi: Worker Threads

import { Worker, isMainThread, parentPort, workerData } from "worker_threads";

if (isMainThread) {
  // Main thread — buat worker
  const worker = new Worker("./heavy-task.js", {
    workerData: { iterations: 1_000_000 },
  });

  worker.on("message", (result) => {
    console.log("Hasil dari worker:", result);
  });

  worker.on("error", (err) => {
    console.error("Worker error:", err);
  });

  worker.on("exit", (code) => {
    console.log("Worker selesai dengan code:", code);
  });
} else {
  // Worker thread — terima data dan proses
  const { iterations } = workerData;
  let sum = 0;
  for (let i = 0; i < iterations; i++) {
    sum += i;
  }
  parentPort.postMessage(sum);
}

Komunikasi Worker ↔ Main Thread:

• workerData — kirim data awal ke worker
• parentPort.postMessage() — worker kirim hasil ke main
• worker.postMessage() — main kirim pesan ke worker
• parentPort.on("message") — worker terima pesan dari main

Worker Threads vs child_process:

Kapan pakai Worker Threads:

• Kalkulasi matematika berat
• Image/video processing
• Parsing file besar (CSV, XML)
• Enkripsi/hashing

Kapan TIDAK perlu Worker Threads:

• I/O operations (sudah non-blocking)
• Database queries (driver sudah async)
• HTTP requests (sudah async)

Worker pool pattern:

import { Worker } from "worker_threads";

function runWorker(data) {
  return new Promise((resolve, reject) => {
    const worker = new Worker("./task.js", { workerData: data });
    worker.on("message", resolve);
    worker.on("error", reject);
  });
}

app.get("/compute", async (req, res) => {
  const result = await runWorker({ n: 1000000 });
  res.json({ result });
});