/** * The `worker_threads` module enables the use of threads that execute JavaScript * in parallel. To access it: * * ```js * const worker = require('worker_threads'); * ``` * * Workers (threads) are useful for performing CPU-intensive JavaScript operations. * They do not help much with I/O-intensive work. The Node.js built-in * asynchronous I/O operations are more efficient than Workers can be. * * Unlike `child_process` or `cluster`, `worker_threads` can share memory. They do * so by transferring `ArrayBuffer` instances or sharing `SharedArrayBuffer`instances. * * ```js * const { * Worker, isMainThread, parentPort, workerData * } = require('worker_threads'); * * if (isMainThread) { * module.exports = function parseJSAsync(script) { * return new Promise((resolve, reject) => { * const worker = new Worker(__filename, { * workerData: script * }); * worker.on('message', resolve); * worker.on('error', reject); * worker.on('exit', (code) => { * if (code !== 0) * reject(new Error(`Worker stopped with exit code ${code}`)); * }); * }); * }; * } else { * const { parse } = require('some-js-parsing-library'); * const script = workerData; * parentPort.postMessage(parse(script)); * } * ``` * * The above example spawns a Worker thread for each `parseJSAsync()` call. In * practice, use a pool of Workers for these kinds of tasks. Otherwise, the * overhead of creating Workers would likely exceed their benefit. * * When implementing a worker pool, use the `AsyncResource` API to inform * diagnostic tools (e.g. to provide asynchronous stack traces) about the * correlation between tasks and their outcomes. See `"Using AsyncResource for a Worker thread pool"` in the `async_hooks` documentation for an example implementation. * * Worker threads inherit non-process-specific options by default. Refer to `Worker constructor options` to know how to customize worker thread options, * specifically `argv` and `execArgv` options. * @see [source](https://github.com/nodejs/node/blob/v18.0.0/lib/worker_threads.js) */ declare module 'worker_threads' { import { Blob } from 'node:buffer'; import { Context } from 'node:vm'; import { EventEmitter } from 'node:events'; import { EventLoopUtilityFunction } from 'node:perf_hooks'; import { FileHandle } from 'node:fs/promises'; import { Readable, Writable } from 'node:stream'; import { URL } from 'node:url'; import { X509Certificate } from 'node:crypto'; const isMainThread: boolean; const parentPort: null | MessagePort; const resourceLimits: ResourceLimits; const SHARE_ENV: unique symbol; const threadId: number; const workerData: any; /** * Instances of the `worker.MessageChannel` class represent an asynchronous, * two-way communications channel. * The `MessageChannel` has no methods of its own. `new MessageChannel()`yields an object with `port1` and `port2` properties, which refer to linked `MessagePort` instances. * * ```js * const { MessageChannel } = require('worker_threads'); * * const { port1, port2 } = new MessageChannel(); * port1.on('message', (message) => console.log('received', message)); * port2.postMessage({ foo: 'bar' }); * // Prints: received { foo: 'bar' } from the `port1.on('message')` listener * ``` * @since v10.5.0 */ class MessageChannel { readonly port1: MessagePort; readonly port2: MessagePort; } interface WorkerPerformance { eventLoopUtilization: EventLoopUtilityFunction; } type TransferListItem = ArrayBuffer | MessagePort | FileHandle | X509Certificate | Blob; /** * Instances of the `worker.MessagePort` class represent one end of an * asynchronous, two-way communications channel. It can be used to transfer * structured data, memory regions and other `MessagePort`s between different `Worker` s. * * This implementation matches [browser `MessagePort`](https://developer.mozilla.org/en-US/docs/Web/API/MessagePort) s. * @since v10.5.0 */ class MessagePort extends EventEmitter { /** * Disables further sending of messages on either side of the connection. * This method can be called when no further communication will happen over this`MessagePort`. * * The `'close' event` is emitted on both `MessagePort` instances that * are part of the channel. * @since v10.5.0 */ close(): void; /** * Sends a JavaScript value to the receiving side of this channel.`value` is transferred in a way which is compatible with * the [HTML structured clone algorithm](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm). * * In particular, the significant differences to `JSON` are: * * * `value` may contain circular references. * * `value` may contain instances of builtin JS types such as `RegExp`s,`BigInt`s, `Map`s, `Set`s, etc. * * `value` may contain typed arrays, both using `ArrayBuffer`s * and `SharedArrayBuffer`s. * * `value` may contain [`WebAssembly.Module`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Module) instances. * * `value` may not contain native (C++-backed) objects other than: * * ```js * const { MessageChannel } = require('worker_threads'); * const { port1, port2 } = new MessageChannel(); * * port1.on('message', (message) => console.log(message)); * * const circularData = {}; * circularData.foo = circularData; * // Prints: { foo: [Circular] } * port2.postMessage(circularData); * ``` * * `transferList` may be a list of [`ArrayBuffer`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer), `MessagePort` and `FileHandle` objects. * After transferring, they are not usable on the sending side of the channel * anymore (even if they are not contained in `value`). Unlike with `child processes`, transferring handles such as network sockets is currently * not supported. * * If `value` contains [`SharedArrayBuffer`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer) instances, those are accessible * from either thread. They cannot be listed in `transferList`. * * `value` may still contain `ArrayBuffer` instances that are not in`transferList`; in that case, the underlying memory is copied rather than moved. * * ```js * const { MessageChannel } = require('worker_threads'); * const { port1, port2 } = new MessageChannel(); * * port1.on('message', (message) => console.log(message)); * * const uint8Array = new Uint8Array([ 1, 2, 3, 4 ]); * // This posts a copy of `uint8Array`: * port2.postMessage(uint8Array); * // This does not copy data, but renders `uint8Array` unusable: * port2.postMessage(uint8Array, [ uint8Array.buffer ]); * * // The memory for the `sharedUint8Array` is accessible from both the * // original and the copy received by `.on('message')`: * const sharedUint8Array = new Uint8Array(new SharedArrayBuffer(4)); * port2.postMessage(sharedUint8Array); * * // This transfers a freshly created message port to the receiver. * // This can be used, for example, to create communication channels between * // multiple `Worker` threads that are children of the same parent thread. * const otherChannel = new MessageChannel(); * port2.postMessage({ port: otherChannel.port1 }, [ otherChannel.port1 ]); * ``` * * The message object is cloned immediately, and can be modified after * posting without having side effects. * * For more information on the serialization and deserialization mechanisms * behind this API, see the `serialization API of the v8 module`. * @since v10.5.0 */ postMessage(value: any, transferList?: ReadonlyArray): void; /** * Opposite of `unref()`. Calling `ref()` on a previously `unref()`ed port does_not_ let the program exit if it's the only active handle left (the default * behavior). If the port is `ref()`ed, calling `ref()` again has no effect. * * If listeners are attached or removed using `.on('message')`, the port * is `ref()`ed and `unref()`ed automatically depending on whether * listeners for the event exist. * @since v10.5.0 */ ref(): void; /** * Calling `unref()` on a port allows the thread to exit if this is the only * active handle in the event system. If the port is already `unref()`ed calling`unref()` again has no effect. * * If listeners are attached or removed using `.on('message')`, the port is`ref()`ed and `unref()`ed automatically depending on whether * listeners for the event exist. * @since v10.5.0 */ unref(): void; /** * Starts receiving messages on this `MessagePort`. When using this port * as an event emitter, this is called automatically once `'message'`listeners are attached. * * This method exists for parity with the Web `MessagePort` API. In Node.js, * it is only useful for ignoring messages when no event listener is present. * Node.js also diverges in its handling of `.onmessage`. Setting it * automatically calls `.start()`, but unsetting it lets messages queue up * until a new handler is set or the port is discarded. * @since v10.5.0 */ start(): void; addListener(event: 'close', listener: () => void): this; addListener(event: 'message', listener: (value: any) => void): this; addListener(event: 'messageerror', listener: (error: Error) => void): this; addListener(event: string | symbol, listener: (...args: any[]) => void): this; emit(event: 'close'): boolean; emit(event: 'message', value: any): boolean; emit(event: 'messageerror', error: Error): boolean; emit(event: string | symbol, ...args: any[]): boolean; on(event: 'close', listener: () => void): this; on(event: 'message', listener: (value: any) => void): this; on(event: 'messageerror', listener: (error: Error) => void): this; on(event: string | symbol, listener: (...args: any[]) => void): this; once(event: 'close', listener: () => void): this; once(event: 'message', listener: (value: any) => void): this; once(event: 'messageerror', listener: (error: Error) => void): this; once(event: string | symbol, listener: (...args: any[]) => void): this; prependListener(event: 'close', listener: () => void): this; prependListener(event: 'message', listener: (value: any) => void): this; prependListener(event: 'messageerror', listener: (error: Error) => void): this; prependListener(event: string | symbol, listener: (...args: any[]) => void): this; prependOnceListener(event: 'close', listener: () => void): this; prependOnceListener(event: 'message', listener: (value: any) => void): this; prependOnceListener(event: 'messageerror', listener: (error: Error) => void): this; prependOnceListener(event: string | symbol, listener: (...args: any[]) => void): this; removeListener(event: 'close', listener: () => void): this; removeListener(event: 'message', listener: (value: any) => void): this; removeListener(event: 'messageerror', listener: (error: Error) => void): this; removeListener(event: string | symbol, listener: (...args: any[]) => void): this; off(event: 'close', listener: () => void): this; off(event: 'message', listener: (value: any) => void): this; off(event: 'messageerror', listener: (error: Error) => void): this; off(event: string | symbol, listener: (...args: any[]) => void): this; } interface WorkerOptions { /** * List of arguments which would be stringified and appended to * `process.argv` in the worker. This is mostly similar to the `workerData` * but the values will be available on the global `process.argv` as if they * were passed as CLI options to the script. */ argv?: any[] | undefined; env?: NodeJS.Dict | typeof SHARE_ENV | undefined; eval?: boolean | undefined; workerData?: any; stdin?: boolean | undefined; stdout?: boolean | undefined; stderr?: boolean | undefined; execArgv?: string[] | undefined; resourceLimits?: ResourceLimits | undefined; /** * Additional data to send in the first worker message. */ transferList?: TransferListItem[] | undefined; /** * @default true */ trackUnmanagedFds?: boolean | undefined; } interface ResourceLimits { /** * The maximum size of a heap space for recently created objects. */ maxYoungGenerationSizeMb?: number | undefined; /** * The maximum size of the main heap in MB. */ maxOldGenerationSizeMb?: number | undefined; /** * The size of a pre-allocated memory range used for generated code. */ codeRangeSizeMb?: number | undefined; /** * The default maximum stack size for the thread. Small values may lead to unusable Worker instances. * @default 4 */ stackSizeMb?: number | undefined; } /** * The `Worker` class represents an independent JavaScript execution thread. * Most Node.js APIs are available inside of it. * * Notable differences inside a Worker environment are: * * * The `process.stdin`, `process.stdout` and `process.stderr` may be redirected by the parent thread. * * The `require('worker_threads').isMainThread` property is set to `false`. * * The `require('worker_threads').parentPort` message port is available. * * `process.exit()` does not stop the whole program, just the single thread, * and `process.abort()` is not available. * * `process.chdir()` and `process` methods that set group or user ids * are not available. * * `process.env` is a copy of the parent thread's environment variables, * unless otherwise specified. Changes to one copy are not visible in other * threads, and are not visible to native add-ons (unless `worker.SHARE_ENV` is passed as the `env` option to the `Worker` constructor). * * `process.title` cannot be modified. * * Signals are not delivered through `process.on('...')`. * * Execution may stop at any point as a result of `worker.terminate()` being invoked. * * IPC channels from parent processes are not accessible. * * The `trace_events` module is not supported. * * Native add-ons can only be loaded from multiple threads if they fulfill `certain conditions`. * * Creating `Worker` instances inside of other `Worker`s is possible. * * Like [Web Workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API) and the `cluster module`, two-way communication can be * achieved through inter-thread message passing. Internally, a `Worker` has a * built-in pair of `MessagePort` s that are already associated with each other * when the `Worker` is created. While the `MessagePort` object on the parent side * is not directly exposed, its functionalities are exposed through `worker.postMessage()` and the `worker.on('message')` event * on the `Worker` object for the parent thread. * * To create custom messaging channels (which is encouraged over using the default * global channel because it facilitates separation of concerns), users can create * a `MessageChannel` object on either thread and pass one of the`MessagePort`s on that `MessageChannel` to the other thread through a * pre-existing channel, such as the global one. * * See `port.postMessage()` for more information on how messages are passed, * and what kind of JavaScript values can be successfully transported through * the thread barrier. * * ```js * const assert = require('assert'); * const { * Worker, MessageChannel, MessagePort, isMainThread, parentPort * } = require('worker_threads'); * if (isMainThread) { * const worker = new Worker(__filename); * const subChannel = new MessageChannel(); * worker.postMessage({ hereIsYourPort: subChannel.port1 }, [subChannel.port1]); * subChannel.port2.on('message', (value) => { * console.log('received:', value); * }); * } else { * parentPort.once('message', (value) => { * assert(value.hereIsYourPort instanceof MessagePort); * value.hereIsYourPort.postMessage('the worker is sending this'); * value.hereIsYourPort.close(); * }); * } * ``` * @since v10.5.0 */ class Worker extends EventEmitter { /** * If `stdin: true` was passed to the `Worker` constructor, this is a * writable stream. The data written to this stream will be made available in * the worker thread as `process.stdin`. * @since v10.5.0 */ readonly stdin: Writable | null; /** * This is a readable stream which contains data written to `process.stdout` inside the worker thread. If `stdout: true` was not passed to the `Worker` constructor, then data is piped to the * parent thread's `process.stdout` stream. * @since v10.5.0 */ readonly stdout: Readable; /** * This is a readable stream which contains data written to `process.stderr` inside the worker thread. If `stderr: true` was not passed to the `Worker` constructor, then data is piped to the * parent thread's `process.stderr` stream. * @since v10.5.0 */ readonly stderr: Readable; /** * An integer identifier for the referenced thread. Inside the worker thread, * it is available as `require('worker_threads').threadId`. * This value is unique for each `Worker` instance inside a single process. * @since v10.5.0 */ readonly threadId: number; /** * Provides the set of JS engine resource constraints for this Worker thread. * If the `resourceLimits` option was passed to the `Worker` constructor, * this matches its values. * * If the worker has stopped, the return value is an empty object. * @since v13.2.0, v12.16.0 */ readonly resourceLimits?: ResourceLimits | undefined; /** * An object that can be used to query performance information from a worker * instance. Similar to `perf_hooks.performance`. * @since v15.1.0, v14.17.0, v12.22.0 */ readonly performance: WorkerPerformance; /** * @param filename The path to the Worker’s main script or module. * Must be either an absolute path or a relative path (i.e. relative to the current working directory) starting with ./ or ../, * or a WHATWG URL object using file: protocol. If options.eval is true, this is a string containing JavaScript code rather than a path. */ constructor(filename: string | URL, options?: WorkerOptions); /** * Send a message to the worker that is received via `require('worker_threads').parentPort.on('message')`. * See `port.postMessage()` for more details. * @since v10.5.0 */ postMessage(value: any, transferList?: ReadonlyArray): void; /** * Opposite of `unref()`, calling `ref()` on a previously `unref()`ed worker does_not_ let the program exit if it's the only active handle left (the default * behavior). If the worker is `ref()`ed, calling `ref()` again has * no effect. * @since v10.5.0 */ ref(): void; /** * Calling `unref()` on a worker allows the thread to exit if this is the only * active handle in the event system. If the worker is already `unref()`ed calling`unref()` again has no effect. * @since v10.5.0 */ unref(): void; /** * Stop all JavaScript execution in the worker thread as soon as possible. * Returns a Promise for the exit code that is fulfilled when the `'exit' event` is emitted. * @since v10.5.0 */ terminate(): Promise; /** * Returns a readable stream for a V8 snapshot of the current state of the Worker. * See `v8.getHeapSnapshot()` for more details. * * If the Worker thread is no longer running, which may occur before the `'exit' event` is emitted, the returned `Promise` is rejected * immediately with an `ERR_WORKER_NOT_RUNNING` error. * @since v13.9.0, v12.17.0 * @return A promise for a Readable Stream containing a V8 heap snapshot */ getHeapSnapshot(): Promise; addListener(event: 'error', listener: (err: Error) => void): this; addListener(event: 'exit', listener: (exitCode: number) => void): this; addListener(event: 'message', listener: (value: any) => void): this; addListener(event: 'messageerror', listener: (error: Error) => void): this; addListener(event: 'online', listener: () => void): this; addListener(event: string | symbol, listener: (...args: any[]) => void): this; emit(event: 'error', err: Error): boolean; emit(event: 'exit', exitCode: number): boolean; emit(event: 'message', value: any): boolean; emit(event: 'messageerror', error: Error): boolean; emit(event: 'online'): boolean; emit(event: string | symbol, ...args: any[]): boolean; on(event: 'error', listener: (err: Error) => void): this; on(event: 'exit', listener: (exitCode: number) => void): this; on(event: 'message', listener: (value: any) => void): this; on(event: 'messageerror', listener: (error: Error) => void): this; on(event: 'online', listener: () => void): this; on(event: string | symbol, listener: (...args: any[]) => void): this; once(event: 'error', listener: (err: Error) => void): this; once(event: 'exit', listener: (exitCode: number) => void): this; once(event: 'message', listener: (value: any) => void): this; once(event: 'messageerror', listener: (error: Error) => void): this; once(event: 'online', listener: () => void): this; once(event: string | symbol, listener: (...args: any[]) => void): this; prependListener(event: 'error', listener: (err: Error) => void): this; prependListener(event: 'exit', listener: (exitCode: number) => void): this; prependListener(event: 'message', listener: (value: any) => void): this; prependListener(event: 'messageerror', listener: (error: Error) => void): this; prependListener(event: 'online', listener: () => void): this; prependListener(event: string | symbol, listener: (...args: any[]) => void): this; prependOnceListener(event: 'error', listener: (err: Error) => void): this; prependOnceListener(event: 'exit', listener: (exitCode: number) => void): this; prependOnceListener(event: 'message', listener: (value: any) => void): this; prependOnceListener(event: 'messageerror', listener: (error: Error) => void): this; prependOnceListener(event: 'online', listener: () => void): this; prependOnceListener(event: string | symbol, listener: (...args: any[]) => void): this; removeListener(event: 'error', listener: (err: Error) => void): this; removeListener(event: 'exit', listener: (exitCode: number) => void): this; removeListener(event: 'message', listener: (value: any) => void): this; removeListener(event: 'messageerror', listener: (error: Error) => void): this; removeListener(event: 'online', listener: () => void): this; removeListener(event: string | symbol, listener: (...args: any[]) => void): this; off(event: 'error', listener: (err: Error) => void): this; off(event: 'exit', listener: (exitCode: number) => void): this; off(event: 'message', listener: (value: any) => void): this; off(event: 'messageerror', listener: (error: Error) => void): this; off(event: 'online', listener: () => void): this; off(event: string | symbol, listener: (...args: any[]) => void): this; } interface BroadcastChannel extends NodeJS.RefCounted {} /** * Instances of `BroadcastChannel` allow asynchronous one-to-many communication * with all other `BroadcastChannel` instances bound to the same channel name. * * ```js * 'use strict'; * * const { * isMainThread, * BroadcastChannel, * Worker * } = require('worker_threads'); * * const bc = new BroadcastChannel('hello'); * * if (isMainThread) { * let c = 0; * bc.onmessage = (event) => { * console.log(event.data); * if (++c === 10) bc.close(); * }; * for (let n = 0; n < 10; n++) * new Worker(__filename); * } else { * bc.postMessage('hello from every worker'); * bc.close(); * } * ``` * @since v15.4.0 */ class BroadcastChannel { readonly name: string; /** * Invoked with a single \`MessageEvent\` argument when a message is received. * @since v15.4.0 */ onmessage: (message: unknown) => void; /** * Invoked with a received message cannot be deserialized. * @since v15.4.0 */ onmessageerror: (message: unknown) => void; constructor(name: string); /** * Closes the `BroadcastChannel` connection. * @since v15.4.0 */ close(): void; /** * @since v15.4.0 * @param message Any cloneable JavaScript value. */ postMessage(message: unknown): void; } /** * Mark an object as not transferable. If `object` occurs in the transfer list of * a `port.postMessage()` call, it is ignored. * * In particular, this makes sense for objects that can be cloned, rather than * transferred, and which are used by other objects on the sending side. * For example, Node.js marks the `ArrayBuffer`s it uses for its `Buffer pool` with this. * * This operation cannot be undone. * * ```js * const { MessageChannel, markAsUntransferable } = require('worker_threads'); * * const pooledBuffer = new ArrayBuffer(8); * const typedArray1 = new Uint8Array(pooledBuffer); * const typedArray2 = new Float64Array(pooledBuffer); * * markAsUntransferable(pooledBuffer); * * const { port1 } = new MessageChannel(); * port1.postMessage(typedArray1, [ typedArray1.buffer ]); * * // The following line prints the contents of typedArray1 -- it still owns * // its memory and has been cloned, not transferred. Without * // `markAsUntransferable()`, this would print an empty Uint8Array. * // typedArray2 is intact as well. * console.log(typedArray1); * console.log(typedArray2); * ``` * * There is no equivalent to this API in browsers. * @since v14.5.0, v12.19.0 */ function markAsUntransferable(object: object): void; /** * Transfer a `MessagePort` to a different `vm` Context. The original `port`object is rendered unusable, and the returned `MessagePort` instance * takes its place. * * The returned `MessagePort` is an object in the target context and * inherits from its global `Object` class. Objects passed to the [`port.onmessage()`](https://developer.mozilla.org/en-US/docs/Web/API/MessagePort/onmessage) listener are also created in the * target context * and inherit from its global `Object` class. * * However, the created `MessagePort` no longer inherits from [`EventTarget`](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget), and only * [`port.onmessage()`](https://developer.mozilla.org/en-US/docs/Web/API/MessagePort/onmessage) can be used to receive * events using it. * @since v11.13.0 * @param port The message port to transfer. * @param contextifiedSandbox A `contextified` object as returned by the `vm.createContext()` method. */ function moveMessagePortToContext(port: MessagePort, contextifiedSandbox: Context): MessagePort; /** * Receive a single message from a given `MessagePort`. If no message is available,`undefined` is returned, otherwise an object with a single `message` property * that contains the message payload, corresponding to the oldest message in the`MessagePort`’s queue. * * ```js * const { MessageChannel, receiveMessageOnPort } = require('worker_threads'); * const { port1, port2 } = new MessageChannel(); * port1.postMessage({ hello: 'world' }); * * console.log(receiveMessageOnPort(port2)); * // Prints: { message: { hello: 'world' } } * console.log(receiveMessageOnPort(port2)); * // Prints: undefined * ``` * * When this function is used, no `'message'` event is emitted and the`onmessage` listener is not invoked. * @since v12.3.0 */ function receiveMessageOnPort(port: MessagePort): | { message: any; } | undefined; type Serializable = string | object | number | boolean | bigint; /** * Within a worker thread, `worker.getEnvironmentData()` returns a clone * of data passed to the spawning thread's `worker.setEnvironmentData()`. * Every new `Worker` receives its own copy of the environment data * automatically. * * ```js * const { * Worker, * isMainThread, * setEnvironmentData, * getEnvironmentData, * } = require('worker_threads'); * * if (isMainThread) { * setEnvironmentData('Hello', 'World!'); * const worker = new Worker(__filename); * } else { * console.log(getEnvironmentData('Hello')); // Prints 'World!'. * } * ``` * @since v15.12.0, v14.18.0 * @param key Any arbitrary, cloneable JavaScript value that can be used as a {Map} key. */ function getEnvironmentData(key: Serializable): Serializable; /** * The `worker.setEnvironmentData()` API sets the content of`worker.getEnvironmentData()` in the current thread and all new `Worker`instances spawned from the current context. * @since v15.12.0, v14.18.0 * @param key Any arbitrary, cloneable JavaScript value that can be used as a {Map} key. * @param value Any arbitrary, cloneable JavaScript value that will be cloned and passed automatically to all new `Worker` instances. If `value` is passed as `undefined`, any previously set value * for the `key` will be deleted. */ function setEnvironmentData(key: Serializable, value: Serializable): void; } declare module 'node:worker_threads' { export * from 'worker_threads'; }