Web worker pool
npm install @esportsplus/workersLightweight, type-safe worker pool for Browser and Node.js. Features proxy-based API, automatic transferable detection, task cancellation, timeouts, and typed per-task events.
``bash`
pnpm add @esportsplus/workers
`ts
// worker.ts
import { onmessage } from '@esportsplus/workers';
let actions = {
math: {
add(a: number, b: number) {
return a + b;
},
multiply(a: number, b: number) {
return a * b;
}
},
async fetchData(url: string) {
let response = await fetch(url);
return response.json();
}
};
onmessage(actions);
export type Actions = typeof actions;
`
`ts
// main.ts
import { pool } from '@esportsplus/workers';
import type { Actions } from './worker';
let workers = pool
// Call methods - all return TaskPromise (extends Promise)
let sum = await workers().math.add(1, 2); // 3
let product = await workers().math.multiply(3, 4); // 12
let data = await workers().fetchData('https://api.example.com');
`
`ts`
let workers = pool
limit: 4, // Max concurrent workers (default: CPU cores - 1)
idleTimeout: 30000 // Terminate idle workers after 30s (default: 0 = never)
});
| Option | Type | Default | Description |
|--------|------|---------|-------------|
| limit | number | cpus - 1 | Maximum worker threads |idleTimeout
| | number | 0 | MS before idle workers terminate (0 = keep alive) |
Cancel tasks that take too long:
`ts`
// Task fails after 5 seconds
let result = await workers({ timeout: 5000 }).math.add(1, 2);
Cancel tasks programmatically:
`ts
let controller = new AbortController();
// Start task
let promise = workers({ signal: controller.signal }).fetchData(url);
// Cancel it
controller.abort();
// Promise rejects with abort error
await promise; // throws '@esportsplus/workers: task aborted'
`
`ts
let controller = new AbortController();
let result = await workers({
signal: controller.signal,
timeout: 10000
}).processData(largeDataset);
`
Transferable objects (ArrayBuffer, MessagePort, ImageBitmap, OffscreenCanvas) are automatically detected and transferred for zero-copy performance. No manual configuration required.
`ts
// ArrayBuffer - automatically transferred (sender loses access)
let buffer = new ArrayBuffer(1024 1024 8);
let result = await workers().processBuffer(buffer);
// buffer.byteLength === 0 after transfer
// OffscreenCanvas - automatically transferred
let canvas = document.createElement('canvas');
let offscreen = canvas.transferControlToOffscreen();
await workers().render(offscreen);
`
The library recursively scans arguments and return values to find transferables in nested objects and arrays.
Workers can dispatch typed events back to the main thread during task execution. Events are received on the TaskPromise returned by each method call.
`ts
// types.ts
type Events = {
progress: { percent: number; message: string };
log: { level: string; text: string };
};
export type { Events };
`
Access dispatch via this context in your action functions:
`ts
// worker.ts
import { onmessage, WorkerContext } from '@esportsplus/workers';
import type { Events } from './types';
let actions = {
async processItems(this: WorkerContext
for (let i = 0, n = items.length; i < n; i++) {
this.dispatch('progress', { percent: (i / n) * 100, message: Processing ${items[i]} });Item ${i + 1} of ${n}
this.dispatch('log', { level: 'info', text: });
// ... processing ...
}
this.dispatch('progress', { percent: 100, message: 'Complete' });
return { processed: items.length };
}
};
onmessage
export type Actions = typeof actions;
`
Events are scoped to individual task executions via the TaskPromise.on() method:
`ts
// main.ts
import { pool } from '@esportsplus/workers';
import type { Actions } from './worker';
import type { Events } from './types';
let workers = pool
// Subscribe to events on the task promise (chainable)
let result = await workers()
.processItems(['a', 'b', 'c'])
.on('progress', (data) => {
console.log(${data.percent}%: ${data.message});[${data.level}] ${data.text}
})
.on('log', (data) => {
console.log();
});
console.log(result); // { processed: 3 }
`
`ts
let stats = workers.stats();
// {
// workers: 4, // Total workers
// busy: 2, // Currently executing
// idle: 2, // Available for work
// queued: 10, // Tasks waiting
// completed: 150 // Total completed
// }
`
Waits for running tasks, rejects queued tasks:
`ts`
await workers.shutdown();
Works in both Browser (Web Workers) and Node.js (worker_threads):
`ts
// Browser - use URL path
let workers = pool
// Node.js - use file URL
let workers = pool
`
Workers auto-detect their context - no configuration needed:
`ts
// worker.ts - works in both environments
import { onmessage } from '@esportsplus/workers';
onmessage(actions); // Auto-detects self (browser) or parentPort (node)
`
Data is serialized using the structured clone algorithm (native to postMessage). Transferable objects are automatically detected and transferred for zero-copy performance.
`ts
// Main thread - pass plain values
let result = await workers().process({ name: 'test', values: [1, 2, 3] });
// Worker - receives plain values, returns plain values
let actions = {
process(data: { name: string; values: number[] }) {
return { sum: data.values.reduce((a, b) => a + b, 0) };
}
};
`
Supported types: primitives, objects, arrays, Date, Map, Set, ArrayBuffer, TypedArrays, and more (see structured clone docs).
Creates a worker pool.
Type Parameters:
- T - Actions type (for method typing)E
- - Events type (for event typing)
Returns: Callable proxy with pool methods
`ts
let workers = pool
// Execute tasks - returns TaskPromise
workers(taskOptions?).path.to.method(args);
// Pool methods
workers.stats(); // Get pool statistics
workers.shutdown(); // Graceful shutdown
`
Sets up worker-side message handler.
Type Parameters:
- E - Events type (for dispatch typing)
`ts`
onmessage
Extended Promise returned by task execution. Supports event subscriptions.
`ts
let promise = workers().someMethod(args);
// Subscribe to events (chainable)
promise.on('eventName', (data) => { ... });
// Still a regular Promise
let result = await promise;
`
Type for the this context available in worker actions:
`ts
type WorkerContext
dispatch:
};
// Usage in action (declare this type for TypeScript)
let actions = {
myAction(this: WorkerContext
this.dispatch('eventName', eventData);
return result;
}
};
`
- Type-safe - Full TypeScript inference for methods, args, returns, and events
- Proxy API - Chain paths like workers().namespace.method()`
- Auto transferables - ArrayBuffer, MessagePort, ImageBitmap, OffscreenCanvas detected automatically
- Auto pooling - Workers created on-demand, recycled automatically
- Task queue - Backpressure handling when workers busy
- Cancellation - AbortSignal support for task cancellation
- Timeouts - Per-task timeout configuration
- Per-task events - Typed worker-to-main communication scoped to each task
- Idle timeout - Auto-terminate unused workers
- Crash recovery - Failed workers replaced automatically
- Cross-platform - Browser Web Workers + Node.js worker_threads