Rate Limiter

Token bucket rate limiter for controlling request rates

go (1.21) 2025-11-12 rate-limiting concurrency token-bucket goroutine

Description

A token bucket rate limiter implementation in Go. Controls the rate of operations by maintaining a bucket of tokens that refill over time.

Features

  • Token bucket algorithm
  • Configurable rate and burst size
  • Thread-safe operations
  • Time-based token refill

Code

RAW 
package ratelimitimport (	"sync"	"time")type RateLimiter struct {	mu          sync.Mutex	tokens      float64	maxTokens   float64	refillRate  float64	lastRefill  time.Time}func NewRateLimiter(rate float64, burst int) *RateLimiter {	return &RateLimiter{		tokens:     float64(burst),		maxTokens:  float64(burst),		refillRate: rate,		lastRefill: time.Now(),	}}func (rl *RateLimiter) refill() {	now := time.Now()	elapsed := now.Sub(rl.lastRefill).Seconds()	tokensToAdd := elapsed * rl.refillRate		rl.mu.Lock()	defer rl.mu.Unlock()		rl.tokens = min(rl.tokens+tokensToAdd, rl.maxTokens)	rl.lastRefill = now}func (rl *RateLimiter) Allow() bool {	rl.refill()		rl.mu.Lock()	defer rl.mu.Unlock()		if rl.tokens >= 1.0 {		rl.tokens -= 1.0		return true	}	return false}func (rl *RateLimiter) Wait(ctx context.Context) error {	for !rl.Allow() {		select {		case <-ctx.Done():			return ctx.Err()		case <-time.After(time.Second / time.Duration(rl.refillRate)):		}	}	return nil}func min(a, b float64) float64 {	if a < b {		return a	}	return b}
RAW 
package mainimport (	"context"	"fmt"	"time"	"ratelimit")func main() {	limiter := ratelimit.NewRateLimiter(10, 20)	ctx := context.Background()		for i := 0; i < 50; i++ {		if limiter.Allow() {			fmt.Printf("Request %d allowed\n", i+1)		} else {			fmt.Printf("Request %d rate limited\n", i+1)			limiter.Wait(ctx)		}	}}

Comments

No comments yet. Be the first to comment!