promise-throttle-bucket

Throttles a promise-returning function using the token-bucket algorithm.

Motivation

Many AWS APIs are throttled using the token-bucket algorithm. For instance, to prevent hitting the EC2 rate limits, the functions that call the AWS API can be wrapped and throttled.

Install

npm install promise-throttle-bucket

Usage

const pThrottleBucket = require('promise-throttle-bucket')

const throttledFn = pThrottleBucket(
  describeEc2Instance,
  { max: 100, refill: 20 }
)

Promise.all([/* array of 150 instances */].map(throttledFn))
    // After 0s, described instances 0-99
    // After 1s, described instances 100-119
    // After 2s, described instances 120-139
    // After 3s, described instances 140-150
  .then(function (instances) {
    // Resolves after all the instances were described.
  })

API

pThrottleBucket(fn, options)

Returns a throttled function.

fn

Type: Function

A function.

options

Type: object

options.max

Type: number

The maximum number of tokens in the bucket.

options.refill

Type: number

The number of refill tokens per interval in milliseconds.

options.interval?

Type: number Default: 1000

The refill interval in milliseconds.

throttledFn

Type: function

The throttled version of fn. It resolves when fn() resolves and rejects if it rejects. The time it takes to settle depends on how many calls are in the queue and the throttling parameters.