@arrows/worker/spawn.js

Simple, promise-based API for native worker threads (with pools)

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const worker_threads_1 = require("worker_threads");
const os_1 = require("os");
const defaultConfig = {
    poolSize: os_1.cpus().length,
};
/**
 * Spawns a workers pool from worker defined in a separate file,
 * returns a function that handles messaging and returns responses as promises.
 *
 * Use when you want to separate worker definition from spawning a thread pool.
 *
 * @param fileName Path to a worker definition file created with `work` function
 * @param config Configuration options
 * @returns Async function that communicates with worker threads
 */
const spawn = (fileName, config = {}) => {
    const cfg = { ...defaultConfig, ...config };
    const { poolSize, transfer, ...options } = cfg;
    if (poolSize <= 0) {
        throw new Error("Pool size has to be > 0");
    }
    const promises = new Map();
    const workers = Array.from({ length: poolSize }, () => new worker_threads_1.Worker(fileName, options).on("message", ([id, data, error]) => {
        if (error) {
            promises.get(id).reject(error);
        }
        else {
            promises.get(id).resolve(data);
        }
        promises.delete(id);
    }));
    let workerIndex = 0;
    const fn = (payload, transferList) => {
        const id = process.hrtime.bigint();
        const promise = new Promise((resolve, reject) => {
            promises.set(id, { resolve, reject });
        });
        workers[workerIndex].postMessage([id, payload], transferList);
        workerIndex = (workerIndex + 1) % poolSize;
        return promise;
    };
    const task = Object.assign(fn, {
        ref() {
            workers.forEach((worker) => worker.ref());
        },
        unref() {
            workers.forEach((worker) => worker.unref());
        },
        terminate() {
            return Promise.all(workers.map((worker) => worker.terminate()));
        },
    });
    return task;
};
exports.spawn = spawn;
exports.default = spawn;