Rolling Rate Limiter with Redis

Rolling Rate Limiter is a module for Node.js which provides a basic, but a solid rate limiter using sliding windows stored in Redis. It was inspired from ClassDojo Rate Limiter, but several issues has been fixed like :

• Removing closure to fix a memory leak if a lot of users request the limit
• Instead of fetching the whole range (with ZRANGE(key, 0, -1)) and then count the number of elements, we use ZCARD, and only fetch the first timestamp and the last timestamp, so we avoid a large operation in Redis and save a lot of memory if we use a large limit (like 3000 request / min).
• Fixing a bug with interval in microseconds instead of milliseconds
• Avoid a race condition with ZREM and ZADD

Requirements

• NodeJS >= 0.10.x
• Redis >= 2.6.12

Examples

var RateLimiter = require("redis-ratelimit");
var redis = require('ioredis'); // or node_redis or any Redis Client

var client = redis.createClient({
  port: 6379,
  host: '127.0.0.1'
});

var limiter = RateLimiter({
  redis: client, 
  namespace: "my-limiter", // optional
  interval: 1000, // in miliseconds (= 1s)
  maxInInterval: 10, // 10 actions max
  minDifference: 100 // optional: the minimum time (in miliseconds) between any two actions
});

client.on('ready', function() {
 limiter('my-limit', function(err, timeLeft) {
  if(err) {
    throw err;
  }
  
  // timeLeft is in ms
  if(timeLeft > 0) {
    console.log('Rate limit exceeded, Please wait %s secs', timeLeft/1000);
  } else {
    // Do your stuff
  }
  
 });
});