Rate Limit Redis

This module is a Redis based rate limiter for Node.js and Express. It is intended to be used where your web severs are distributed across multiple systems or nodes (such as in load balancing) and there needs to be a centralized location to store request counts.

How it works

1. When a request is made, a new temporary record is stored in Redis. This record is defined by the IP address of the request and will expire.
2. If a second request is made before the first expires, the record count is incremented.
3. For each request made within the rate limit window, the record is incremented.
4. If the record count reaches the max limit before expiring, then a 429 error status is returned.

Install

npm install --save @jwerre/rate-limit-redis

Usage

const {rateLimitRedis} = require('@jwerre/rate_limit_redis');
const app = require('express')();
const rateLimitArgs = {
  redis: {
    url: 'redis://127.0.0.1:6379',
  },
  timeframe: 60,
  limit: 120,
  headers: true,
  whitelist: [ '192.168.20.20' ],
  customRoutes: [
    {
      path: '/stingy/rate/limit',
      method: 'POST',
      timeframe: 30,
      limit: 5,
    },
    {
      path: '/loose/rate/limit',
      method: 'PUT',
      timeframe: 120,
      limit: 500,
    {
      path: /^\/regex\/[0-9]{5,10}\/?$/,
      method: 'GET',
      timeframe: 60,
      limit: 25,
    },
    {
      path: '/ignore/rate/limit',
      method: 'GET',
      ignore: true
    },
  ]
};

// use trust proxy if behind load balancer
app.enable('trust proxy');

app.use( rateLimitRedis(rateLimitArgs) );

app.get('/', (req, res) => { res.send('OK') ); });

const server = app.listen( 8080 );

server.on('error', () => {
  // rateLimitRedis is added to Node's global scope 
  // (https://nodejs.org/docs/latest-v14.x/api/globals.html) so you can close 
  // the connection properly
  global.rateLimitRedis.disconnect();
});

Alternate Usage

If you need a little more control, you can instantiate the RateLimitRedis class yourself.

const {RateLimitRedis} = require('@jwerre/rate-limit-redis');

const rateLimitRedis = new RateLimitRedis({
  redis: {
    // see: https://github.com/redis/node-redis/blob/master/docs/client-configuration.md
    socket: {
      host: 'localhost',
      port: 6379,
    }
  },
  timeframe: 60,
  limit: 120,
  autoConnect: false,
});

rateLimitRedis.connect().then( () => {

  rateLimitRedis.process(<SOME_HTTP_REQUEST>)
    .then((res) => {
      console.log(res);
    })
    .catch((err) => {
      console.error(err);
    })

});

Arguments

Data Type	Argument	Description
Object	redis	Redis options https://github.com/redis/node-redis/blob/master/docs/client-configuration.md
String	namespace	String to prepend to the Redis key e.g.: 'rate-limit:<USER-IP>'.
Number	timeframe	Rate limit window in seconds.
Number	limit	Maximum amount of requests allowed within timeframe.
Boolean	headers	Whether to set rate limit headers or not.
Boolean	autoConnect	Whether to automaitcally connect to redis before proccess http request (default: true).
[String]	whitelist	A list of IP addresses where rate limit should not apply. This may be useful if you have automated tasks, probes or health checks coming from known IPs and you don't want to apply a rate limit to them.
[Object]	customRoutes	A list of routes where you can set custom rate limits. This will create a new rate limit with a unique key based on the IP, method and path.
String|RegExp	customRoutes.path	The path to ignore (required). Note: Do not user trailing slash.
String	customRoutes.method	The request method of the ignored path (default: get).
Number	customRoutes.timeframe	Rate limit window in seconds for custom route.
Number	customRoutes.limit	Maximum amount of requests allowed within timeframe for custom route.
Boolean	customRoutes.ignore	Rate limit request to this custom route will be ignored. Be careful with this one.

Methods

process(request)

Process HTTP request.

Argumements

HTTP request: The http request to rate limit

Returns

Promise: Object containing rate limit information e.g.:

{
  status: 200,
  limit: 100,
  timeframe: 2,
  remaining: 99,
  retry: Number // if status is 429
  error: Error // if status is 429
}

disconnect()

Close redis connection.

Returns

Promise

Accuracy

This module uses Redis Expire to manage rate limit requests. If using Redis 2.4 or lower, accuracy could be as much as 1 second off.

Testing

Ensure Node.js and Redis are installed and running. Then execute the following commands:

npm install
npm test

Benchmark

TODO: Set up benchmark test.