JavaScript Concurrency Control Libraries Comparison
p-limit vs async vs p-queue vs p-all
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What's JavaScript Concurrency Control Libraries?

Concurrency control libraries in JavaScript provide mechanisms to manage asynchronous operations efficiently, allowing developers to execute multiple tasks in parallel while controlling the flow and resource usage. These libraries help prevent callback hell, manage promises, and optimize performance by limiting the number of concurrent operations, making them essential for building scalable applications that require handling multiple asynchronous tasks without overwhelming system resources.

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p-limit120,146,0952,08710.3 kB62 days agoMIT
async55,464,37828,209808 kB64 months agoMIT
p-queue6,724,3013,50836 kB46a year agoMIT
p-all1,488,9223205.42 kB12 years agoMIT
Feature Comparison: p-limit vs async vs p-queue vs p-all

Concurrency Control

  • p-limit:

    P-Limit is specifically designed to limit the number of concurrent promises, allowing you to specify how many can run at once, which helps in preventing resource overload and managing API rate limits effectively.

  • async:

    Async provides various functions to manage concurrency, allowing you to execute tasks in series or parallel, but it does not impose strict limits on the number of concurrent operations, which can lead to resource exhaustion if not managed carefully.

  • p-queue:

    P-Queue manages a queue of asynchronous tasks and allows you to set concurrency limits, ensuring that only a specified number of tasks run simultaneously while maintaining the order of execution.

  • p-all:

    P-All allows you to run multiple promises in parallel without any concurrency limits, making it straightforward to handle a batch of asynchronous tasks, but it does not provide control over how many tasks run simultaneously.

Ease of Use

  • p-limit:

    P-Limit is easy to use and integrates seamlessly with promise-based workflows, providing a clear and concise way to limit concurrency without much overhead.

  • async:

    Async has a rich API with many utility functions, which may introduce a steeper learning curve for new users, but it offers great flexibility for complex workflows.

  • p-queue:

    P-Queue has a straightforward API for managing task queues, but understanding its prioritization and concurrency features may require some additional learning.

  • p-all:

    P-All is very simple to use, requiring minimal setup to run multiple promises in parallel, making it accessible for developers looking for straightforward concurrency handling.

Performance Optimization

  • p-limit:

    P-Limit optimizes performance by controlling the number of concurrent operations, ensuring that the system is not overloaded, which can lead to better overall performance in resource-constrained environments.

  • async:

    Async can lead to performance bottlenecks if not used judiciously, especially with its parallel execution capabilities, which may overwhelm resources if too many tasks are executed simultaneously.

  • p-queue:

    P-Queue allows for prioritization of tasks and manages concurrency effectively, which can lead to better performance in scenarios where task execution order matters.

  • p-all:

    P-All is efficient for running multiple promises in parallel, but it does not optimize for resource usage, which can lead to performance issues if the number of promises is very high.

Use Cases

  • p-limit:

    P-Limit is perfect for use cases where you need to make API calls or perform operations that have rate limits, allowing you to control the flow of requests effectively.

  • async:

    Async is best suited for complex workflows that require a combination of parallel and series execution patterns, especially when working with collections and needing to perform multiple operations on them.

  • p-queue:

    P-Queue is suited for applications where task order and resource management are critical, such as job processing systems or when interacting with external services that require strict request handling.

  • p-all:

    P-All is ideal for scenarios where you need to execute a batch of independent asynchronous tasks and wait for all of them to complete, such as fetching multiple resources at once.

Error Handling

  • p-limit:

    P-Limit allows you to handle errors in a controlled manner, as it limits the number of concurrent operations, making it easier to manage error states without overwhelming the system.

  • async:

    Async provides various error handling mechanisms, allowing you to manage errors in asynchronous flows effectively, but it can be complex to implement in deeply nested workflows.

  • p-queue:

    P-Queue provides a structured way to handle errors in queued tasks, allowing you to retry or manage failed tasks systematically, which is beneficial for long-running processes.

  • p-all:

    P-All resolves with an array of results, making it straightforward to handle errors, but it does not provide built-in error handling for individual promises, which may require additional logic.

How to Choose: p-limit vs async vs p-queue vs p-all
  • p-limit:

    Choose P-Limit if you need to control the number of concurrent promises that can be executed at any given time, making it ideal for scenarios where you want to avoid overwhelming an API or a resource with too many simultaneous requests.

  • async:

    Choose Async if you need a comprehensive utility library for managing asynchronous control flow, including functions for parallel, series, and waterfall execution patterns, along with a rich set of utilities for working with collections and functions.

  • p-queue:

    Choose P-Queue if you require a more structured approach to manage a queue of asynchronous tasks, allowing you to control concurrency and prioritize tasks, which is particularly useful in scenarios where task execution order and resource management are critical.

  • p-all:

    Choose P-All if you want a simple and efficient way to run multiple promises in parallel and wait for all of them to resolve, particularly useful when you need to handle a batch of asynchronous tasks without any concurrency limits.

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 p-queue

p-queue is a promise-based queue implementation for managing asynchronous tasks in JavaScript. It allows developers to control the concurrency of tasks, ensuring that a specified number of tasks run simultaneously while others wait in line. This is particularly useful when dealing with APIs or other asynchronous operations that may have rate limits or require controlled execution. With features like priority support and the ability to pause and resume queues, p-queue provides a flexible solution for managing complex asynchronous workflows.

There are several alternatives to p-queue that also provide functionality for managing asynchronous tasks:

  • async is a widely-used utility module that provides a variety of functions to work with asynchronous JavaScript. It includes methods for controlling concurrency, such as async.eachLimit and async.parallelLimit, which allow you to run multiple asynchronous operations in parallel with a specified limit. While async is a powerful library with a broad range of features, it may be considered more heavyweight compared to p-queue, especially if you only need simple queuing functionality.

  • p-all is a lightweight utility that allows you to run multiple promise-returning functions concurrently and returns a promise that resolves when all of the promises have resolved. It provides a simple way to manage concurrency without the additional features found in p-queue. If your primary need is to run a set of promises concurrently without the overhead of a full queue implementation, p-all is an excellent choice.

  • p-limit is another minimalist utility that allows you to limit the number of concurrent promises. It creates a function that can be called with promise-returning functions, ensuring that only a specified number of them are executed at any given time. This is particularly useful for controlling resource usage when dealing with APIs or other asynchronous tasks. If you need a straightforward way to limit concurrency without the additional features of a queue, p-limit is an ideal solution.

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

Similar Npm Packages to p-all

p-all is a utility library that allows you to run multiple Promise-returning functions in parallel, with the ability to limit the number of concurrent executions. This is particularly useful when you need to perform multiple asynchronous operations but want to avoid overwhelming the system or hitting API rate limits. By using p-all, developers can easily manage concurrency while ensuring that all promises are resolved.

While p-all is a powerful tool for managing parallel promises, there are several alternatives in the npm ecosystem that offer similar functionalities. Here are a few notable ones:

  • p-map is a library that allows you to map over an array of items and execute an asynchronous function for each item in parallel. It provides options to control the concurrency level, making it a great choice when you want to process a collection of items without blocking the event loop. If you need to transform data asynchronously while managing how many promises run concurrently, p-map is an excellent option.

  • p-queue is a promise queue that allows you to manage a queue of asynchronous tasks. It provides features such as concurrency control, priority levels, and the ability to pause and resume the queue. If your application requires more complex task management, such as prioritizing certain tasks or controlling the order of execution, p-queue is a robust solution.

  • p-series is a utility that runs an array of Promise-returning functions in series, meaning each function will only start after the previous one has completed. This is useful when the order of execution matters or when you want to limit the number of concurrent tasks to one. If you need to ensure that tasks are executed sequentially, p-series is the right choice.

To explore how these packages compare, check out the comparison: Comparing p-all vs p-map vs p-queue vs p-series.

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
Minimum: 1

Concurrency limit.

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.

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 teardown 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.

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.

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-all - Run promise-returning & async functions concurrently with optional limited concurrency
  • More…
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