koa-grounded

A distributed rate-limit middleware for Koa 2, inspired by Dcard's intern preliminary project.

Watch it in action on asciinema

Quick Start

Install

$ yarn add koa-grounded

Basic Usage

const Koa = require('koa');
const Grounded = require('koa-grounded');
 
const app = new Koa();
 
// Remember to set app.proxy flag if you are using under a reverse proxy
app.proxy = true;
 
const RateLimiter = Grounded({
  partitionKey: 'grounded',
  ratelimit: 1000,
  globalEXP: 60 * 60 * 1000 * 1000, // expiration time in μs
  timeout: 2000,
  cacheSize: 500,
  dbStr: 'redis://127.0.0.1:6379/',
  verbose: true,
});
 
// Grounded Middleware
app.use(RateLimiter);
 
// Ping Pong
app.use(async (ctx) => {
  ctx.body = 'Pong!';
});
 
// Using IPv4 instead of IPv6;
app.listen(4000, '0.0.0.0');
 
console.log('listening on port 4000');

See the document #API for further informations.

API

Param	Type	Description
partitionKey	string	A partition key for current Rate-Limiter to listen, will create ${partitionKey}-exp, ${partitionKey}-remaining and ${partitionKey}-ban keys on Redis Instance, and subscribe to ${partitionKey}-ban and ${partitionKey}-unban channels
ratelimit	number	Ratelimit for each user's session
globalEXP	number	Expiration time for user's ratelimit session, in microseconds(10^-6 seconds) unit
timeout	number	Worker-Redis synchronization intervals, in miliseconds(10^-3 seconds) unit, it is suggested to modify the value as fast as the worker localQueue size reaches MTU size
cacheSize	number	Maxmimum key size stored on local LRU cache
dbStr	string	Connection string to the Redis instance, see luin/ioredis#connect-to-redis for further information
verbose	boolean	Showing access log informations or not

Running tests

$ yarn test

Overview

Concept

Introduction

Since Redis is fast enough for its in-memory data operations, the bottleneck of a Redis connection is the Round-Trip Time(RTT), which may dramatically affects throughputs of services having Redis as the centralized datastore.

This approach implemented a Eventually consistency and Availability-Partition tolerance(AP) approach using pipelined Lua scripts, LRU cache and Pub/Sub to optimize the throughput of the Rate-Limit service, and it is also capable of:

• sharing states among all workers
• key-space partitioning
• Ratelimiting

As a result, we can achieve 10x faster than normal non-pipelined Redis approach with such optimization(See #Benchmark for details).

Implementation

WIP

Benchmark

One Worker, local Redis

(Redis Instance on Intel Core i7 9850H, 16GB RAM, macOS 10.15.3)

Ping RTT

--- localhost ping statistics ---
20 packets transmitted, 20 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.050/0.093/0.113/0.017 ms

using koajs/ratelimit

➜  ~ wrk -t12 -c1200 -d5s
Running 5s test
  12 threads and 1200 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    34.73ms   20.94ms 627.03ms   81.09%
    Req/Sec   760.13    236.27     1.42k    74.61%
  39505 requests in 5.07s, 11.05MB read
  Socket errors: connect 0, read 623, write 0, timeout 0
  Non-2xx or 3xx responses: 38505
Requests/sec:   7794.90
Transfer/sec:      2.18MB

our implementation

➜  ~ wrk -t12 -c1200 -d5s
Running 5s test
  12 threads and 1200 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    13.74ms   11.99ms 479.43ms   98.00%
    Req/Sec     1.53k   592.69     3.90k    77.36%
  84128 requests in 5.10s, 18.43MB read
  Socket errors: connect 0, read 529, write 0, timeout 0
  Non-2xx or 3xx responses: 83128
Requests/sec:  16500.27
Transfer/sec:      3.61MB

One Worker, remote Redis

(Redis Instance located on TANet, vSphere6.7, 1vCPU 2GB RAM, CentOS7 + docker 19.03)

Ping RTT

--- Remote-Redis ping statistics ---
20 packets transmitted, 20 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 19.858/67.130/250.806/61.965 ms

using koajs/ratelimit

➜  ~ wrk -t12 -c1200 -d5s
Running 5s test
  12 threads and 1200 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   129.69ms   56.67ms 632.29ms   71.43%
    Req/Sec   155.99     71.33   323.00     65.16%
  7712 requests in 5.10s, 2.10MB read
  Socket errors: connect 0, read 625, write 0, timeout 0
  Non-2xx or 3xx responses: 6712
Requests/sec:   1513.19
Transfer/sec:    422.69KB

our implementation

➜  ~ wrk -t12 -c1200 -d5s
Running 5s test
  12 threads and 1200 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    16.75ms   12.07ms 449.36ms   76.08%
    Req/Sec     1.48k   526.48     3.13k    74.82%
  81097 requests in 5.10s, 17.76MB read
  Socket errors: connect 0, read 613, write 0, timeout 0
  Non-2xx or 3xx responses: 80097
Requests/sec:  15899.12
Transfer/sec:      3.48MB

Roadmap

• Worker-Threads
• Increase Unit Test Coverage
• Support for other Redis Client
• LUA script for cleaning expired keys on Redis

License

MIT