Run CPU work on workers

You will move a CPU-heavy step out of a request handler onto a worker thread, declare the module, set a time limit and test it. It takes about 10 minutes and needs no account.

You need

• A MainSDK app with a main.yaml.
• A function that burns CPU for more than a few milliseconds and needs no network, database or secret. A worker may not call other MainSDK interfaces.

1. Declare the module

workers:
  size: auto
  timeout: 10s
  modules: ["src/workers/*.worker.ts"]

2. Write the worker module

import { worker } from "mainsdk/workers";

export default worker((rows: number[][], ctx) => {
  ctx.log.info("scoring", { rows: rows.length });
  return rows.map((r) => r.reduce((a, b) => a + b, 0));
});

3. Call it

import { workers } from "mainsdk";

export function score(rows: number[][], signal?: AbortSignal) {
  return workers.run<number[][], number[]>("./src/workers/score.worker.ts", rows, { signal });
}

Pass plain data in and out. Never pass a secret: it fails with MAIN-WORKER-0004.

4. Test it

createTestApp() runs the task inline. Add workers: "threads" to prove it on a real thread.

import { createTestApp } from "@mainsdk/testing";

const app = createTestApp({ yaml: "schema: 1\nproject: t\nworkers:\n  modules: [src/workers/*.worker.ts]\n", workers: "threads" });
const out = await app.workers.run("./src/workers/score.worker.ts", [[1, 2], [3]]);

Check it worked

• npx mainsdk check has no MAIN-WORKER- finding, and npx mainsdk discover lists the module.
• workers.snapshot() shows completed rising and threads back to 0 after the idle time.
• A task that loops past the timeout fails with MAIN-WORKER-0005 and the next task still runs.