Implementing Rate Limiting in Go

Introduction

The lab demonstrates how to implement rate limiting in Go using goroutines, channels, and tickers.

Skills Graph

Rate Limiting

The problem is to limit the handling of incoming requests to maintain quality of service and control resource utilization.

• Go programming language
• Basic understanding of goroutines, channels, and tickers

## Running our program we see the first batch of requests
## handled once every ~200 milliseconds as desired.
$ go run rate-limiting.go
request 1 2012-10-19 00:38:18.687438 +0000 UTC
request 2 2012-10-19 00:38:18.887471 +0000 UTC
request 3 2012-10-19 00:38:19.087238 +0000 UTC
request 4 2012-10-19 00:38:19.287338 +0000 UTC
request 5 2012-10-19 00:38:19.487331 +0000 UTC

## For the second batch of requests we serve the first
## 3 immediately because of the burstable rate limiting,
## then serve the remaining 2 with ~200ms delays each.
request 1 2012-10-19 00:38:20.487578 +0000 UTC
request 2 2012-10-19 00:38:20.487645 +0000 UTC
request 3 2012-10-19 00:38:20.487676 +0000 UTC
request 4 2012-10-19 00:38:20.687483 +0000 UTC
request 5 2012-10-19 00:38:20.887542 +0000 UTC

There is the full code below:

// [_Rate limiting_](https://en.wikipedia.org/wiki/Rate_limiting)
// is an important mechanism for controlling resource
// utilization and maintaining quality of service. Go
// elegantly supports rate limiting with goroutines,
// channels, and [tickers](tickers).

package main

import (
	"fmt"
	"time"
)

func main() {

	// First we'll look at basic rate limiting. Suppose
	// we want to limit our handling of incoming requests.
	// We'll serve these requests off a channel of the
	// same name.
	requests := make(chan int, 5)
	for i := 1; i <= 5; i++ {
		requests <- i
	}
	close(requests)

	// This `limiter` channel will receive a value
	// every 200 milliseconds. This is the regulator in
	// our rate limiting scheme.
	limiter := time.Tick(200 * time.Millisecond)

	// By blocking on a receive from the `limiter` channel
	// before serving each request, we limit ourselves to
	// 1 request every 200 milliseconds.
	for req := range requests {
		<-limiter
		fmt.Println("request", req, time.Now())
	}

	// We may want to allow short bursts of requests in
	// our rate limiting scheme while preserving the
	// overall rate limit. We can accomplish this by
	// buffering our limiter channel. This `burstyLimiter`
	// channel will allow bursts of up to 3 events.
	burstyLimiter := make(chan time.Time, 3)

	// Fill up the channel to represent allowed bursting.
	for i := 0; i < 3; i++ {
		burstyLimiter <- time.Now()
	}

	// Every 200 milliseconds we'll try to add a new
	// value to `burstyLimiter`, up to its limit of 3.
	go func() {
		for t := range time.Tick(200 * time.Millisecond) {
			burstyLimiter <- t
		}
	}()

	// Now simulate 5 more incoming requests. The first
	// 3 of these will benefit from the burst capability
	// of `burstyLimiter`.
	burstyRequests := make(chan int, 5)
	for i := 1; i <= 5; i++ {
		burstyRequests <- i
	}
	close(burstyRequests)
	for req := range burstyRequests {
		<-burstyLimiter
		fmt.Println("request", req, time.Now())
	}
}

Summary

The lab demonstrates how to implement rate limiting in Go using goroutines, channels, and tickers to control resource utilization and maintain quality of service.