p-limit vs async vs promise-queue vs bluebird vs promise-limit
JavaScript Promise and Async Control Libraries
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JavaScript Promise and Async Control Libraries

JavaScript Promise and Async Control Libraries are tools that help manage asynchronous operations in JavaScript, providing more control over how and when these operations are executed. They offer features like limiting concurrency, queuing tasks, and handling promises more efficiently, which can improve performance and resource management in applications. These libraries are particularly useful in scenarios where you need to perform multiple asynchronous tasks but want to avoid overwhelming the system or running into issues like callback hell or unhandled promise rejections. They provide a more structured and manageable way to work with asynchronous code, making it easier to write, read, and maintain.

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p-limit442,781,588-16.1 kB-2 months agoMIT
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promise-limit0---8 years agoISC

Feature Comparison: p-limit vs async vs promise-queue vs bluebird vs promise-limit

Concurrency Control

  • p-limit:

    p-limit is specifically designed for limiting the concurrency of promise-based tasks. You can create a limit function that enforces a maximum number of concurrent promises, making it simple to control resource usage.

  • async:

    The async library provides various functions for controlling concurrency, such as async.parallelLimit and async.eachLimit, allowing you to specify limits on how many tasks run simultaneously.

  • promise-queue:

    promise-queue manages concurrency by queuing tasks and executing them in order with a specified limit on how many run simultaneously. This ensures that tasks are completed in the order they were added.

  • bluebird:

    bluebird offers concurrency control through its Promise.map method, which allows you to set a concurrency limit while mapping over an array of values, executing promises in parallel up to the specified limit.

  • promise-limit:

    promise-limit provides a straightforward way to limit the number of concurrent promises. It exports a function that takes a limit and returns a wrapper function to control concurrency when executing promises.

Task Queuing

  • p-limit:

    p-limit does not provide task queuing features. It focuses solely on limiting concurrency for promise-based tasks without managing their execution order.

  • async:

    async supports task queuing through its queue and priorityQueue functions, allowing you to create queues with customizable concurrency and priority levels.

  • promise-queue:

    promise-queue is designed for task queuing, ensuring that tasks are executed in the order they are added to the queue. It allows you to set a concurrency limit while maintaining the order of execution.

  • bluebird:

    bluebird does not have built-in task queuing, but you can implement it using its promise chaining and mapping features. The library focuses more on promise management than queuing.

  • promise-limit:

    promise-limit does not include task queuing capabilities. It is designed for simple concurrency limiting without queuing tasks for later execution.

Error Handling

  • p-limit:

    p-limit handles errors in promise-based tasks by allowing them to be rejected as usual. It does not provide special error handling features but works seamlessly with standard promise error handling.

  • async:

    async provides robust error handling mechanisms, including support for error-first callbacks, try/catch in async functions, and the ability to handle errors in parallel and series tasks.

  • promise-queue:

    promise-queue handles errors by allowing rejected promises to propagate through the queue. It does not provide specialized error handling but ensures that errors are managed in the order tasks are executed.

  • bluebird:

    bluebird offers advanced error handling features, including promise cancellation, error propagation, and the ability to catch errors at different stages of promise execution. It also supports unhandled rejection tracking.

  • promise-limit:

    promise-limit allows errors to be handled by the promises it manages. It does not introduce any special error handling mechanisms, relying on standard promise behavior.

Performance

  • p-limit:

    p-limit is lightweight and introduces minimal overhead when limiting concurrency. It is designed for performance, making it suitable for scenarios where you need to control concurrency without significant impact on execution speed.

  • async:

    async is efficient for managing asynchronous operations, but its performance can vary depending on the complexity of the tasks and the concurrency settings. It is designed for flexibility rather than raw performance.

  • promise-queue:

    promise-queue is efficient in managing queued tasks, but its performance depends on the concurrency limit and the number of tasks. It is designed to balance order and concurrency without significant overhead.

  • bluebird:

    bluebird is one of the fastest promise libraries available, optimized for performance with features like lazy evaluation, efficient memory usage, and minimal overhead for promise creation and resolution.

  • promise-limit:

    promise-limit is designed to be simple and efficient, with low overhead for limiting concurrent promise execution. It is suitable for performance-sensitive applications that require basic concurrency control.

Ease of Use: Code Examples

  • p-limit:

    Concurrency control with p-limit library

    const pLimit = require('p-limit');

const limit = pLimit(2); // Limit concurrency to 2
const tasks = [
  () => new Promise((resolve) => setTimeout(() => resolve('Task 1 complete'), 1000)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 2 complete'), 500)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 3 complete'), 2000)),
];

const limitedTasks = tasks.map((task) => limit(task));
Promise.all(limitedTasks)
  .then((results) => console.log(results))
  .catch((err) => console.error(err));
  • async:

    Concurrency control with async library

    const async = require('async');

const tasks = [
  (callback) => setTimeout(() => callback(null, 'Task 1 complete'), 1000),
  (callback) => setTimeout(() => callback(null, 'Task 2 complete'), 500),
  (callback) => setTimeout(() => callback(null, 'Task 3 complete'), 2000),
];

// Limit concurrency to 2 tasks at a time
async.parallelLimit(tasks, 2, (err, results) => {
  if (err) console.error(err);
  console.log(results);
});
  • promise-queue:

    Task queuing with promise-queue library

    const PromiseQueue = require('promise-queue');

const queue = new PromiseQueue(2, Infinity); // Limit concurrency to 2
const tasks = [
  () => new Promise((resolve) => setTimeout(() => resolve('Task 1 complete'), 1000)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 2 complete'), 500)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 3 complete'), 2000)),
];

// Add tasks to the queue
const promises = tasks.map((task) => queue.add(task));
Promise.all(promises)
  .then((results) => console.log(results))
  .catch((err) => console.error(err));
  • bluebird:

    Concurrency control with bluebird library

    const Promise = require('bluebird');

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
const tasks = [
  () => delay(1000).then(() => 'Task 1 complete'),
  () => delay(500).then(() => 'Task 2 complete'),
  () => delay(2000).then(() => 'Task 3 complete'),
];

// Limit concurrency to 2 tasks at a time
Promise.map(tasks, (task) => task(), { concurrency: 2 })
  .then((results) => console.log(results))
  .catch((err) => console.error(err));
  • promise-limit:

    Concurrency control with promise-limit library

    const promiseLimit = require('promise-limit');

const limit = promiseLimit(2); // Limit concurrency to 2
const tasks = [
  () => new Promise((resolve) => setTimeout(() => resolve('Task 1 complete'), 1000)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 2 complete'), 500)),
  () => new Promise((resolve) => setTimeout(() => resolve('Task 3 complete'), 2000)),
];

const limitedTasks = tasks.map((task) => limit(task));
Promise.all(limitedTasks)
  .then((results) => console.log(results))
  .catch((err) => console.error(err));

How to Choose: p-limit vs async vs promise-queue vs bluebird vs promise-limit

  • p-limit:

    Choose p-limit if you need a simple and lightweight solution for limiting the concurrency of promise-based tasks. It is perfect for scenarios where you want to control the number of promises running simultaneously without adding much overhead.

  • async:

    Choose async if you need a comprehensive toolkit for managing asynchronous operations with a wide range of utilities, including parallel, series, and waterfall execution. It is ideal for complex workflows that require fine-grained control over task execution.

  • promise-queue:

    Choose promise-queue if you need a queue-based approach to managing asynchronous tasks, ensuring that they are executed in order and with a specified concurrency limit. It is ideal for scenarios where task order is important, and you want to prevent resource exhaustion.

  • bluebird:

    Choose bluebird if you want a high-performance promise library that offers advanced features like cancellation, progress tracking, and a rich set of utility methods. It is suitable for applications that require efficient promise handling and want to avoid the limitations of native promises.

  • promise-limit:

    Choose promise-limit if you want a straightforward implementation for limiting the number of concurrent promises. It is easy to use and integrates well with existing promise-based code, making it a good choice for projects that need basic concurrency control.

Similar Npm Packages to p-limit

p-limit is a utility library that allows developers to limit the number of concurrent promises that can be executed at a time. This is particularly useful when dealing with APIs or other asynchronous operations where you want to avoid overwhelming the server or hitting rate limits. By using p-limit, you can control the flow of asynchronous tasks, ensuring that only a specified number of them run concurrently, while the others wait in line until a slot becomes available.

While p-limit is a great tool for managing concurrency, there are other libraries that provide similar functionality. Here are a couple of alternatives:

  • p-queue is a promise queue that allows you to manage the concurrency of asynchronous tasks. It provides a more feature-rich solution than p-limit, with options for prioritizing tasks, setting a maximum concurrency level, and even handling retries. If you need more control over the order and execution of your asynchronous operations, p-queue is an excellent choice. It’s particularly useful for scenarios where you need to manage complex workflows or prioritize certain tasks over others.

  • p-throttle is another alternative that focuses on limiting the rate at which a function can be called. Unlike p-limit, which limits concurrent executions, p-throttle allows you to control how often a function can be invoked over time. This can be particularly useful for scenarios like API rate limiting, where you want to ensure that a function is not called too frequently. If your primary concern is controlling the rate of function execution rather than managing concurrency, p-throttle is the right tool for the job.

To see how p-limit compares with p-queue and p-throttle, check out the comparison: Comparing p-limit vs p-queue vs p-throttle.

Similar Npm Packages to async

async is a utility module that provides powerful functions for working with asynchronous JavaScript. It simplifies the process of managing asynchronous operations, allowing developers to write cleaner and more maintainable code. With features like parallel execution, series execution, and control flow, async is particularly useful for handling complex asynchronous workflows. However, there are several alternatives in the JavaScript ecosystem that also provide similar functionalities. Here are a few notable ones:

  • bluebird is a fully-featured promise library that offers a wide range of utilities for working with promises. It enhances the native Promise functionality by providing additional features such as cancellation, progress tracking, and more robust error handling. bluebird is known for its performance and is a great choice for developers looking for an advanced promise library that can handle complex asynchronous tasks with ease.

  • p-map is a lightweight utility that allows you to map over an array asynchronously, executing a provided function for each element in parallel. It is particularly useful when you need to perform asynchronous operations on an array of items and want to control the concurrency level. p-map is simple to use and can be a great alternative for scenarios where you need to process multiple asynchronous tasks without the overhead of a larger library.

  • q is another promise library that focuses on providing a simple and straightforward API for working with asynchronous code. It was one of the earlier promise libraries in the JavaScript ecosystem and offers features like chaining, error handling, and more. While it may not be as feature-rich as some of the newer libraries, q is still a solid choice for developers looking for a lightweight solution for managing asynchronous operations.

To see how async compares with bluebird, p-map, and q, check out the comparison: Comparing async vs bluebird vs p-map vs q.

Similar Npm Packages to promise-queue

promise-queue is a JavaScript library that helps manage a queue of promises, allowing developers to control the concurrency of asynchronous operations. It provides a simple way to limit the number of promises that can be executed simultaneously, which is particularly useful when dealing with APIs or resources that have rate limits. While promise-queue is effective for managing promise execution, there are several alternatives that offer similar functionality. Here are a few noteworthy options:

  • async is a widely-used utility module that provides powerful functions for working with asynchronous JavaScript. It includes a variety of methods for managing asynchronous control flow, including queues, series, and parallel execution. async is particularly useful for handling complex workflows where you need to manage multiple asynchronous tasks in a structured way. Its extensive feature set makes it suitable for a wide range of scenarios, from simple promise management to complex asynchronous workflows.

  • bottleneck is a rate limiter for JavaScript that provides a robust way to control the execution of asynchronous functions. It allows you to set limits on how many times a function can be called in a given timeframe, making it ideal for scenarios where you need to avoid overwhelming a server or API. bottleneck is highly configurable, allowing you to set different limits for different functions, and it can handle both promise-based and callback-based functions seamlessly.

  • p-queue is a promise queue implementation that allows you to manage the concurrency of promise-based tasks. It provides a simple API for adding tasks to the queue and controlling how many tasks can run simultaneously. p-queue is particularly useful when you need to manage a large number of asynchronous operations while ensuring that you don't exceed certain concurrency limits. Its lightweight nature and focus on promises make it a great alternative to promise-queue.

  • queue-promise is another library designed for managing a queue of promise-based tasks. It allows you to control the concurrency of your asynchronous operations while providing a straightforward API for adding tasks to the queue. queue-promise is particularly useful for scenarios where you need to ensure that tasks are executed in a specific order while managing concurrency effectively.

To explore how promise-queue compares with async, bottleneck, p-queue, and queue-promise, check out the comparison: Comparing async vs bottleneck vs p-queue vs promise-queue vs queue-promise.

Similar Npm Packages to bluebird

bluebird is a fully-featured promise library for JavaScript that provides a powerful and flexible way to work with asynchronous operations. It enhances the native JavaScript promises by adding a wide range of features, such as cancellation, progress reporting, and more robust error handling. Bluebird is particularly useful for developers who need to manage complex asynchronous workflows and want to take advantage of its performance optimizations.

While Bluebird is a popular choice for promise management, there are several alternatives available in the JavaScript ecosystem. Here are a few noteworthy options:

  • lie is a lightweight promise library that aims to provide a simple and minimalistic implementation of the Promise/A+ specification. It is designed for developers who need a straightforward promise solution without the additional features and overhead that come with larger libraries like Bluebird. Lie is particularly useful for smaller projects or when you want to keep your dependencies minimal.

  • q is another promise library that offers a rich set of features for managing asynchronous operations. It was one of the first libraries to implement the promise concept in JavaScript and provides a variety of utilities for working with promises, such as chaining, error handling, and more. Q is a good choice for developers who need a robust promise implementation with a focus on compatibility and performance.

  • rsvp is a promise library that was created to provide a simple and reliable implementation of promises for JavaScript. It includes features like promise chaining, error handling, and the ability to handle multiple promises concurrently. RSVP is particularly useful for developers who want a straightforward promise solution that is easy to use and integrates well with existing codebases.

  • when is a promise library that focuses on providing a powerful and flexible way to work with asynchronous operations. It offers features like chaining, error handling, and the ability to combine multiple promises. When is a great option for developers who need a comprehensive promise library that can handle complex asynchronous workflows.

To see how Bluebird compares with lie, q, rsvp, and when, check out the comparison: Comparing bluebird vs lie vs q vs rsvp vs when.

Similar Npm Packages to promise-limit

promise-limit is a utility library that allows you to limit the number of concurrent promises that can be executed at the same time. This is particularly useful when dealing with APIs or tasks that can overwhelm a server or when you want to manage resource usage more effectively. By controlling the concurrency of promise execution, promise-limit helps improve performance and prevent issues related to too many simultaneous requests.

While promise-limit offers a straightforward solution for managing concurrency, there are several alternatives in the JavaScript ecosystem that provide similar functionalities. Here are a few notable ones:

  • async is a powerful utility module that provides various functions for working with asynchronous JavaScript. It offers a wide range of features, including control flow, concurrency management, and more. With async, you can easily manage the execution of asynchronous tasks, making it suitable for complex workflows. If you need a comprehensive toolkit for handling asynchronous operations, async is a great choice.
  • bluebird is a fully-featured promise library that provides a rich set of features for working with promises, including concurrency control. It allows you to limit the number of concurrent promises and provides additional utilities for managing promise chains. If you are looking for a promise library that offers advanced features and optimizations, bluebird is worth considering.
  • p-limit is a lightweight library that allows you to limit the number of concurrent executions of asynchronous functions. It provides a simple API for creating a limited promise executor, making it easy to manage concurrency in your applications. If you need a minimalistic solution specifically for limiting concurrency, p-limit is an excellent option.
  • promise-queue is a library that provides a queue for managing promises. It allows you to enqueue promises and control the maximum number of concurrent executions. This is particularly useful when you want to ensure that only a specific number of tasks are running at any given time. If you need a queue-based approach to manage promise execution, promise-queue is a solid choice.

To see how promise-limit compares with async, bluebird, p-limit, and promise-queue, check out the comparison: Comparing async vs bluebird vs p-limit vs promise-limit vs promise-queue.

README for p-limit

p-limit

Run multiple promise-returning & async functions with limited concurrency

Works in Node.js and browsers.

Install

npm install p-limit

Usage

import pLimit from 'p-limit';

const limit = pLimit(1);

const input = [
	limit(() => fetchSomething('foo')),
	limit(() => fetchSomething('bar')),
	limit(() => doSomething())
];

// Only one promise is run at once
const result = await Promise.all(input);
console.log(result);

API

pLimit(concurrency) default export

Returns a limit function.

concurrency

Type: number | object
Minimum: 1

Concurrency limit.

You can pass a number or an options object with a concurrency property.

rejectOnClear

Type: boolean
Default: false

Reject pending promises with an AbortError when clearQueue() is called. This is recommended if you await the returned promises, for example with Promise.all, so pending tasks do not remain unresolved after clearQueue().

import pLimit from 'p-limit';

const limit = pLimit({concurrency: 1});

limit(fn, ...args)

Returns the promise returned by calling fn(...args).

fn

Type: Function

Promise-returning/async function.

args

Any arguments to pass through to fn.

Support for passing arguments on to the fn is provided in order to be able to avoid creating unnecessary closures. You probably don't need this optimization unless you're pushing a lot of functions.

Warning: Avoid calling the same limit function inside a function that is already limited by it. This can create a deadlock where inner tasks never run. Use a separate limiter for inner tasks.

limit.map(iterable, mapperFunction)

Process an iterable of inputs with limited concurrency.

The mapper function receives the item value and its index.

Returns a promise equivalent to Promise.all(Array.from(iterable, (item, index) => limit(mapperFunction, item, index))).

If the iterable throws during iteration, the returned promise rejects with that error. Mapper functions that were already scheduled still run, and their results are discarded.

This is a convenience function for processing inputs that arrive in batches. For more complex use cases, see p-map.

limit.activeCount

The number of promises that are currently running.

limit.pendingCount

The number of promises that are waiting to run (i.e. their internal fn was not called yet).

limit.clearQueue()

Discard pending promises that are waiting to run.

This might be useful if you want to tear down the queue at the end of your program's lifecycle or discard any function calls referencing an intermediary state of your app.

Note: This does not cancel promises that are already running.

When rejectOnClear is enabled, pending promises are rejected with an AbortError. This is recommended if you await the returned promises, for example with Promise.all, so pending tasks do not remain unresolved after clearQueue().

limit.concurrency

Get or set the concurrency limit.

limitFunction(fn, options) named export

Returns a function with limited concurrency.

The returned function manages its own concurrent executions, allowing you to call it multiple times without exceeding the specified concurrency limit.

Ideal for scenarios where you need to control the number of simultaneous executions of a single function, rather than managing concurrency across multiple functions.

import {limitFunction} from 'p-limit';

const limitedFunction = limitFunction(async () => {
	return doSomething();
}, {concurrency: 1});

const input = Array.from({length: 10}, limitedFunction);

// Only one promise is run at once.
await Promise.all(input);

fn

Type: Function

Promise-returning/async function.

options

Type: object

concurrency

Type: number
Minimum: 1

Concurrency limit.

rejectOnClear

Type: boolean
Default: false

Reject pending promises with an AbortError when clearQueue() is called. This is recommended if you await the returned promises, for example with Promise.all, so pending tasks do not remain unresolved after clearQueue().

limitedFunction.clearQueue()

Discard pending calls that have not started yet.

When rejectOnClear is enabled, pending promises are rejected with an AbortError. Otherwise, their promises remain unresolved.

This does not cancel calls that are already running.

Recipes

See recipes.md for common use cases and patterns.

FAQ

How is this different from the p-queue package?

This package is only about limiting the number of concurrent executions, while p-queue is a fully featured queue implementation with lots of different options, introspection, and ability to pause the queue.

Related

  • p-throttle - Throttle promise-returning & async functions
  • p-debounce - Debounce promise-returning & async functions
  • p-map - Run promise-returning & async functions concurrently with different inputs
  • p-all - Run promise-returning & async functions concurrently with optional limited concurrency
  • More…
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