Structured Clone vs JSON: Faster Worker Message Passing in Node

// scripts/bench-ipc.ts
import { Worker } from "node:worker_threads";
import { performance } from "node:perf_hooks";

const bytes = Buffer.alloc(1024 * 1024, 1);

function benchJson() {
  const t0 = performance.now();
  for (let i = 0; i < 200; i++) JSON.parse(JSON.stringify({ bytes: bytes.toString("base64") }));
  return performance.now() - t0;
}

function benchClone() {
  const t0 = performance.now();
  for (let i = 0; i < 200; i++) structuredClone({ bytes: bytes.buffer.slice(bytes.byteOffset, bytes.byteOffset + bytes.byteLength) });
  return performance.now() - t0;
}

console.log({ jsonMs: benchJson().toFixed(1), cloneMs: benchClone().toFixed(1) });

// ❌ postMessage(JSON.stringify(huge)) — double tax + string bloat
worker.postMessage(JSON.stringify({ frames }));

// src/worker-pool.ts
import { Worker } from "node:worker_threads";

export function submitJob(worker: Worker, meta: { jobId: string }, payload: Buffer) {
  const ab = payload.buffer.slice(payload.byteOffset, payload.byteOffset + payload.byteLength);
  // ✅ Transfer moves ownership — main thread must not touch `ab` after
  worker.postMessage({ type: "job", meta, payload: ab }, [ab]);
}

// worker.js
import { parentPort } from "node:worker_threads";
parentPort!.on("message", (msg) => {
  if (msg.type !== "job") return;
  const view = Buffer.from(msg.payload);
  const result = processBytes(view);
  const out = result.buffer.slice(result.byteOffset, result.byteOffset + result.byteLength);
  parentPort!.postMessage({ type: "done", jobId: msg.meta.jobId, out }, [out]);
});