simple-async-pool

Easy to use, dependency free and typesafe concurrent pool of async and promise returning functions.

Installation

npm i simple-async-pool

Usage

Using the async pool is really simple. The package exposes a pool function with the following simplified signature:

function pool(options: PoolOptions, consumerFunction, ...input)
function pool(consumerFunction, ...input)

The PoolOptions interface has the following members:

interface PoolOptions {
  output?: 'AsyncIterator' | 'Promise' // defines the return value of the pool function ('Promise' by default)
  concurrency?: number // defines the number of concurrent workers to spawn (1 by default)
}

By default, when no pool options are provided, the pool function returns a promise that resolves the processed input values with a concurrency of one:

import { pool } from 'simple-async-pool'

const consumerFunction = async (input: string) => input
const processedValues = await pool(consumerFunction, 'simple', 'async', 'pool') // if the input values are not strings, typescript complains due to the type missmatch

console.log(processedValues) // [ 'simple', 'async', 'pool' ]

The input values can either be an array (spread syntax), an iterator, an async iterator or a generator function (async/non async).

const processedValues = await pool(consumerFunction, 'simple', 'async', 'pool')

// ...

const input = ['simple', 'async', 'pool']
const processedValues = await pool(consumerFunction, input.values())

// ...

function* input() {
  yield 'simple'
  yield 'async'
  yield 'pool'
}
const processedValues = await pool(consumerFunction, input())

// ...

async function* input() {
  yield 'simple'
  yield 'async'
  yield 'pool'
}
const processedValues = await pool(consumerFunction, input())

console.log(processedValues) // [ 'simple', 'async', 'pool' ]

// ...

function* input() {
  yield 'simple'
  yield 'async'
  yield 'pool'
}
const processedValues = await pool(consumerFunction, input)

// ...

async function* input() {
  yield 'simple'
  yield 'async'
  yield 'pool'
}
const processedValues = await pool(consumerFunction, input)

console.log(processedValues) // [ 'simple', 'async', 'pool' ]

To modify the default behaviour, pool options can be provided as an argument:

const processedValues = await pool({ concurrency: 3 }, consumerFunction, 'simple', 'async', 'pool')
console.log(processedValues) // [ 'simple', 'async', 'pool' ]

Returning an async iterator instead of a promise can be achieved via the pool options too:

const iterator = pool({ concurrency: 3, output: 'AsyncIterator' }, consumerFunction, 'simple', 'async', 'pool')

const values = []
for await (const value of iterator) values.push(value)

When the output property in the options is set to Promise (default behaviour), the order of the output values is guaranteed. When it's AsyncIterator, values are yielded in the order of resolution, so no order can be guaranteed.

License

MIT © Enrique Pöhlmann