call-rate-limiter v0.1.0

Call Rate Limiter

Limit the execution rate of any function by wrapping it with a function that returns Promise. Module uses sliding window rate limiter under the hood. For implementation details check out "How it works" section.

Install

npm install --save call-rate-limiter

Usage

Rate Limited Function

Te basic use case is when you ninteracting with REST api and want to repspect rate limits upfront to prevent be banned by the server.

rateLimit takes limitCount, limitInterval and fn as arguments and returns rate limited function which should be called instead of the function passed as fn.

This means if you call rateLimitedFunc 150 times and only 100 can be called in time, the next 50 calls will be postponed and executed later to respect given rate limits.

import {rateLimit} from 'call-rate-limiter'

const rateLimitedFunc = rateLimit(
  1200,
  60 * 1000,
  id => fetch('https://swapi.co/api/starships/${id}/').then(res => res.json())
)

/*
  fetch Death Star specs, rateLimitedFunc
  transparently passes args to wrapped function
*/
const deathStar = await rateLimitedFunc('9')

Rate Limited API

Suppose, you have a bunch of api calls specified somewhere that you want to call under the same rate limits. It can be easily done with objectRateLimit:

const basePath = 'https://swapi.co/api/'

function character(id) {
  return fetch(`${basePath}/people/${id}`).then(res => res.json())
}

function planet(id) {
  return fetch(`${basePath}/planet/${id}`).then(res => res.json())
}

module.exports = {
  character: character,
  planet: planet
}

objectRateLimit takes object as last argument and return new object with rate-limited functions assigned for same keys:

import {objectRateLimit} from 'call-rate-limiter'
import api from './api'

const rateLimitedApi = objectRateLimit(1200, 60 * 1000, api)

// trying to enumerate all planets in a galaxy far away
let i = 0
while(i < 100000) {
  console.log(await rateLimitedApi.planet(i))
  i++
}

Preventing bursting

Quite often, it is necessary to check not only compliance with the rate limits but also to avoid bursting. We want the function to be called no more than once each N milliseconds. To obtain this wrap your function with throttle than with rateLimit.

import {yourFunction} from 'your-module'

import {rateLimit} from 'call-rate-limiter'
import throttle from 'lodash.throttle'

const waitBetweenCalls = 100 // 100ms
const limitCount = 30 // max 30 calls per minute
const limitInterval = 60 * 1000 // one minute

const rateLimitedNoBurstingFunc = rateLimit(
  limitCount,
  limitInterval,
  throttle(yourFunction, waitBetweenCalls)
)

How it works

TODO: implement