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index.ts
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import {EventEmitter} from 'eventemitter3';
import pTimeout, {TimeoutError} from 'p-timeout';
import {Queue, RunFunction} from './queue.js';
import PriorityQueue from './priority-queue.js';
import {QueueAddOptions, Options, TaskOptions} from './options.js';
type Task<TaskResultType> =
| ((options: TaskOptions) => PromiseLike<TaskResultType>)
| ((options: TaskOptions) => TaskResultType);
/**
The error thrown by `queue.add()` when a job is aborted before it is run. See `signal`.
*/
export class AbortError extends Error {}
type EventName = 'active' | 'idle' | 'empty' | 'add' | 'next' | 'completed' | 'error';
/**
Promise queue with concurrency control.
*/
export default class PQueue<QueueType extends Queue<RunFunction, EnqueueOptionsType> = PriorityQueue, EnqueueOptionsType extends QueueAddOptions = QueueAddOptions> extends EventEmitter<EventName> {
readonly #carryoverConcurrencyCount: boolean;
readonly #isIntervalIgnored: boolean;
#intervalCount = 0;
readonly #intervalCap: number;
readonly #interval: number;
#intervalEnd = 0;
#intervalId?: NodeJS.Timeout;
#timeoutId?: NodeJS.Timeout;
#queue: QueueType;
readonly #queueClass: new () => QueueType;
#pending = 0;
// The `!` is needed because of https://github.com/microsoft/TypeScript/issues/32194
#concurrency!: number;
#isPaused: boolean;
readonly #throwOnTimeout: boolean;
/**
Per-operation timeout in milliseconds. Operations fulfill once `timeout` elapses if they haven't already.
Applies to each future operation.
*/
timeout?: number;
// TODO: The `throwOnTimeout` option should affect the return types of `add()` and `addAll()`
constructor(options?: Options<QueueType, EnqueueOptionsType>) {
super();
// eslint-disable-next-line @typescript-eslint/consistent-type-assertions
options = {
carryoverConcurrencyCount: false,
intervalCap: Number.POSITIVE_INFINITY,
interval: 0,
concurrency: Number.POSITIVE_INFINITY,
autoStart: true,
queueClass: PriorityQueue,
...options,
} as Options<QueueType, EnqueueOptionsType>;
if (!(typeof options.intervalCap === 'number' && options.intervalCap >= 1)) {
throw new TypeError(`Expected \`intervalCap\` to be a number from 1 and up, got \`${options.intervalCap?.toString() ?? ''}\` (${typeof options.intervalCap})`);
}
if (options.interval === undefined || !(Number.isFinite(options.interval) && options.interval >= 0)) {
throw new TypeError(`Expected \`interval\` to be a finite number >= 0, got \`${options.interval?.toString() ?? ''}\` (${typeof options.interval})`);
}
this.#carryoverConcurrencyCount = options.carryoverConcurrencyCount!;
this.#isIntervalIgnored = options.intervalCap === Number.POSITIVE_INFINITY || options.interval === 0;
this.#intervalCap = options.intervalCap;
this.#interval = options.interval;
this.#queue = new options.queueClass!();
this.#queueClass = options.queueClass!;
this.concurrency = options.concurrency!;
this.timeout = options.timeout;
this.#throwOnTimeout = options.throwOnTimeout === true;
this.#isPaused = options.autoStart === false;
}
get #doesIntervalAllowAnother(): boolean {
return this.#isIntervalIgnored || this.#intervalCount < this.#intervalCap;
}
get #doesConcurrentAllowAnother(): boolean {
return this.#pending < this.#concurrency;
}
#next(): void {
this.#pending--;
this.#tryToStartAnother();
this.emit('next');
}
#onResumeInterval(): void {
this.#onInterval();
this.#initializeIntervalIfNeeded();
this.#timeoutId = undefined;
}
get #isIntervalPaused(): boolean {
const now = Date.now();
if (this.#intervalId === undefined) {
const delay = this.#intervalEnd - now;
if (delay < 0) {
// Act as the interval was done
// We don't need to resume it here because it will be resumed on line 160
this.#intervalCount = (this.#carryoverConcurrencyCount) ? this.#pending : 0;
} else {
// Act as the interval is pending
if (this.#timeoutId === undefined) {
this.#timeoutId = setTimeout(
() => {
this.#onResumeInterval();
},
delay,
);
}
return true;
}
}
return false;
}
#tryToStartAnother(): boolean {
if (this.#queue.size === 0) {
// We can clear the interval ("pause")
// Because we can redo it later ("resume")
if (this.#intervalId) {
clearInterval(this.#intervalId);
}
this.#intervalId = undefined;
this.emit('empty');
if (this.#pending === 0) {
this.emit('idle');
}
return false;
}
if (!this.#isPaused) {
const canInitializeInterval = !this.#isIntervalPaused;
if (this.#doesIntervalAllowAnother && this.#doesConcurrentAllowAnother) {
const job = this.#queue.dequeue();
if (!job) {
return false;
}
this.emit('active');
job();
if (canInitializeInterval) {
this.#initializeIntervalIfNeeded();
}
return true;
}
}
return false;
}
#initializeIntervalIfNeeded(): void {
if (this.#isIntervalIgnored || this.#intervalId !== undefined) {
return;
}
this.#intervalId = setInterval(
() => {
this.#onInterval();
},
this.#interval,
);
this.#intervalEnd = Date.now() + this.#interval;
}
#onInterval(): void {
if (this.#intervalCount === 0 && this.#pending === 0 && this.#intervalId) {
clearInterval(this.#intervalId);
this.#intervalId = undefined;
}
this.#intervalCount = this.#carryoverConcurrencyCount ? this.#pending : 0;
this.#processQueue();
}
/**
Executes all queued functions until it reaches the limit.
*/
#processQueue(): void {
// eslint-disable-next-line no-empty
while (this.#tryToStartAnother()) {}
}
get concurrency(): number {
return this.#concurrency;
}
set concurrency(newConcurrency: number) {
if (!(typeof newConcurrency === 'number' && newConcurrency >= 1)) {
throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${newConcurrency}\` (${typeof newConcurrency})`);
}
this.#concurrency = newConcurrency;
this.#processQueue();
}
async #throwOnAbort(signal: AbortSignal): Promise<never> {
return new Promise((_resolve, reject) => {
signal.addEventListener('abort', () => {
// TODO: Reject with signal.throwIfAborted() when targeting Node.js 18
// TODO: Use ABORT_ERR code when targeting Node.js 16 (https://nodejs.org/docs/latest-v16.x/api/errors.html#abort_err)
reject(new AbortError('The task was aborted.'));
}, {once: true});
});
}
/**
Adds a sync or async task to the queue. Always returns a promise.
*/
async add<TaskResultType>(function_: Task<TaskResultType>, options: {throwOnTimeout: true} & Exclude<EnqueueOptionsType, 'throwOnTimeout'>): Promise<TaskResultType>;
async add<TaskResultType>(function_: Task<TaskResultType>, options?: Partial<EnqueueOptionsType>): Promise<TaskResultType | void>;
async add<TaskResultType>(function_: Task<TaskResultType>, options: Partial<EnqueueOptionsType> = {}): Promise<TaskResultType | void> {
options = {
timeout: this.timeout,
throwOnTimeout: this.#throwOnTimeout,
...options,
};
return new Promise((resolve, reject) => {
this.#queue.enqueue(async () => {
this.#pending++;
this.#intervalCount++;
try {
// TODO: Use options.signal?.throwIfAborted() when targeting Node.js 18
if (options.signal?.aborted) {
// TODO: Use ABORT_ERR code when targeting Node.js 16 (https://nodejs.org/docs/latest-v16.x/api/errors.html#abort_err)
throw new AbortError('The task was aborted.');
}
let operation = function_({signal: options.signal});
if (options.timeout) {
operation = pTimeout(Promise.resolve(operation), options.timeout);
}
if (options.signal) {
operation = Promise.race([operation, this.#throwOnAbort(options.signal)]);
}
const result = await operation;
resolve(result);
this.emit('completed', result);
} catch (error: unknown) {
if (error instanceof TimeoutError && !options.throwOnTimeout) {
resolve();
return;
}
reject(error);
this.emit('error', error);
} finally {
this.#next();
}
}, options);
this.emit('add');
this.#tryToStartAnother();
});
}
/**
Same as `.add()`, but accepts an array of sync or async functions.
@returns A promise that resolves when all functions are resolved.
*/
async addAll<TaskResultsType>(
functions: ReadonlyArray<Task<TaskResultsType>>,
options?: {throwOnTimeout: true} & Partial<Exclude<EnqueueOptionsType, 'throwOnTimeout'>>,
): Promise<TaskResultsType[]>
async addAll<TaskResultsType>(
functions: ReadonlyArray<Task<TaskResultsType>>,
options?: Partial<EnqueueOptionsType>,
): Promise<Array<TaskResultsType | void>>;
async addAll<TaskResultsType>(
functions: ReadonlyArray<Task<TaskResultsType>>,
options?: Partial<EnqueueOptionsType>,
): Promise<Array<TaskResultsType | void>> {
return Promise.all(functions.map(async function_ => this.add(function_, options)));
}
/**
Start (or resume) executing enqueued tasks within concurrency limit. No need to call this if queue is not paused (via `options.autoStart = false` or by `.pause()` method.)
*/
start(): this {
if (!this.#isPaused) {
return this;
}
this.#isPaused = false;
this.#processQueue();
return this;
}
/**
Put queue execution on hold.
*/
pause(): void {
this.#isPaused = true;
}
/**
Clear the queue.
*/
clear(): void {
this.#queue = new this.#queueClass();
}
/**
Can be called multiple times. Useful if you for example add additional items at a later time.
@returns A promise that settles when the queue becomes empty.
*/
async onEmpty(): Promise<void> {
// Instantly resolve if the queue is empty
if (this.#queue.size === 0) {
return;
}
await this.#onEvent('empty');
}
/**
@returns A promise that settles when the queue size is less than the given limit: `queue.size < limit`.
If you want to avoid having the queue grow beyond a certain size you can `await queue.onSizeLessThan()` before adding a new item.
Note that this only limits the number of items waiting to start. There could still be up to `concurrency` jobs already running that this call does not include in its calculation.
*/
async onSizeLessThan(limit: number): Promise<void> {
// Instantly resolve if the queue is empty.
if (this.#queue.size < limit) {
return;
}
await this.#onEvent('next', () => this.#queue.size < limit);
}
/**
The difference with `.onEmpty` is that `.onIdle` guarantees that all work from the queue has finished. `.onEmpty` merely signals that the queue is empty, but it could mean that some promises haven't completed yet.
@returns A promise that settles when the queue becomes empty, and all promises have completed; `queue.size === 0 && queue.pending === 0`.
*/
async onIdle(): Promise<void> {
// Instantly resolve if none pending and if nothing else is queued
if (this.#pending === 0 && this.#queue.size === 0) {
return;
}
await this.#onEvent('idle');
}
async #onEvent(event: EventName, filter?: () => boolean): Promise<void> {
return new Promise(resolve => {
const listener = () => {
if (filter && !filter()) {
return;
}
this.off(event, listener);
resolve();
};
this.on(event, listener);
});
}
/**
Size of the queue, the number of queued items waiting to run.
*/
get size(): number {
return this.#queue.size;
}
/**
Size of the queue, filtered by the given options.
For example, this can be used to find the number of items remaining in the queue with a specific priority level.
*/
sizeBy(options: Readonly<Partial<EnqueueOptionsType>>): number {
// eslint-disable-next-line unicorn/no-array-callback-reference
return this.#queue.filter(options).length;
}
/**
Number of running items (no longer in the queue).
*/
get pending(): number {
return this.#pending;
}
/**
Whether the queue is currently paused.
*/
get isPaused(): boolean {
return this.#isPaused;
}
}
// TODO: Rename `DefaultAddOptions` to `QueueAddOptions` in next major version
export {Queue, QueueAddOptions, QueueAddOptions as DefaultAddOptions, Options};