node-throttle

A Node.js module that helps with rate limiting.

The idea behind this module is originally by Chris O'Hara (http://chris6f.com/rate-limiting-with-redis). However, the algorithm he presented can cause false-positive throttling in certain cases.

I adjusted O'Hara's algorithm in this module. This module do not yield false-positive throttling.

Install

Install via Node Package Manager (NPM):

npm install redis-throttle

Quick Example

var Throttle = require('redis-throttle')
Throttle.configure({
  port: 6300,
  host: 'localhost'
})

var key = ip_address + ':' + url
var throttle = new Throttle(key, {
  span: 15 * 60 * 1000, // 15 mins
  accuracy: 10          // margin of error = span / accuracy
})

throttle.increment(1, function(err, count) {
  if (err) throw err;
  var ip = throttle.key.split(':')[0]
  var url = throttle.key.split(':')[1]
  console.log('ip:', ip, 'has visited url:', url, count, 'times', 
    'in', throttle.span / 60 / 1000, 'mins')
})

APIs

Throttle.configure([options])

Intialize the Redis client used by Throttle. Options can include port, host and other options accepted by node_redis. This method should be called before any other methods after requiring the module.

new Throttle(key[, options])

default_options = {
    span: 15 * 60 * 1000, // value should be in milliseconds.
    accuracy: 10          // value should be in milliseconds. ***NOTE: span should be divisible by accuracy***.
}

Create a new throttle instance. Throttle instances with the same key share the same internal status, e.g.

var th1 = new Throttle('key')
var th2 = new Throttle('key')
th1.increment(1, function(err, count) { 
    assert.equal(count, 1)
    th2.increment(1, function(err, count) {
        assert.equal(count, 2)
    })
})

Different accuracies will result in different costs. The complexity of read/increment operation is O(n), where n is accuracy.

read(callback)

Read value of a throttle instance, without increment it.

throttle.read(function(err, count) {
    if (err) throw err
    console.log('current count:', count)
})

increment(n, callback)

Increment value of a throttle instance by n. Returns the resulted value through callback function.

throttle.increment(1, function(err, count) {
    if (err) throw err
    console.log('value after increment: count')
}

Performance

span 10s, accuracy 10 -> 6524 ops/s
span 10s, accuracy 20 -> 5357 ops/s
span 5s, accuracy 10 -> 6023 ops/s

A simple presure test program is included in pressure.js

LICENSE - MIT License

Copyright (c) 2013 Chaoran Yang, charoany (AT) me (dot) com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.