Limitation

An efficient rate limiter with several backends, including a Kademlia DHT.

Features

• Fully synchronous local limit checking for lowest latency and high throughput. Using node 4.3 on a single core, a throughput of about 8 million limit checks per second is typical.
• Backends scale constant in number of requests, and linear in number of keys. Tested with thousands of distinct limits.
• Backends:
  • Resilient Kademlia DHT storage backend using an exponentially decaying counter.
  • Simple and very fast local in-memory storage backend.

Installation

npm install limitation

Usage

Simple in-memory backend:

var Limitation = require('limitation');

var ratelimiter = new Limitation();

if (ratelimiter.isAboveLimit('some_key', 10)) {
  console.log('Limit of 10 req/s exceeded!');
}

Kademlia backend:

var Limitation = require('limitation');

var ratelimiter = new Limitation({
    seeds: [{
        address: 'localhost',
        port: 3050
    },
    // Host names are also supported, expands to some.host:3050
    'some.host'],

    // Optional parameters
    // Address / port to listen on
    // Default: localhost:3050, random port fall-back if port used
    listen: {
        address: '127.0.0.1',
        port: 3050
    },
    // Counter update / block interval; Default: 10000ms
    // Shorter interval means quicker limiting, but also higher load.
    interval: 10000
});

// Returns Promise<Limitation>
ratelimiter.setup();

if (ratelimiter.isAboveLimit('some_key', 10)) {
  console.log('Limit of 10 req/s exceeded!');
}

// Clears any set timers so the process can exit cleanly.
ratelimiter.stop()

See also test/index.js for a runnable Kademlia example. It starts multiple DHT nodes, and you can start multiple copies of the script to play with nodes going down etc.