从 x/time/rate 到分布式滑动窗口：Go 服务限流选型与踩坑实录

package main

import (
	"net/http"
	"golang.org/x/time/rate"
)

var limiter = rate.NewLimiter(rate.Limit(5000), 10000) // r=5000/s, burst=10000

func RateLimitMiddleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !limiter.Allow() {
			http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
			return
		}
		next(w, r)
	}
}

func BenchmarkRateLimiter_Allow(b *testing.B) {
	limiter := rate.NewLimiter(rate.Inf, 1000)
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		limiter.Allow()
	}
}

func BenchmarkRateLimiter_Allow_Parallel(b *testing.B) {
	limiter := rate.NewLimiter(rate.Inf, 1000)
	b.ResetTimer()
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			limiter.Allow()
		}
	})
}

goos: darwin
goarch: arm64
BenchmarkRateLimiter_Allow-10            33682914        35.61 ns/op       0 B/op   0 allocs/op
BenchmarkRateLimiter_Allow_Parallel-10   7124804        168.4 ns/op       0 B/op   0 allocs/op

-- KEYS[1]: 限流 key (如 ratelimit:api:user_123)
-- ARGV[1]: 当前毫秒时间戳
-- ARGV[2]: 窗口大小 (毫秒)
-- ARGV[3]: 窗口内最大允许请求数

local key = KEYS[1]
local now = tonumber(ARGV[1])
local window = tonumber(ARGV[2])
local limit = tonumber(ARGV[3])
local clear_before = now - window

-- 1. 清理过期成员
redis.call('ZREMRANGEBYSCORE', key, 0, clear_before)

-- 2. 获取当前窗口内请求总数
local current_requests = redis.call('ZCARD', key)

-- 3. 判断是否超限
if current_requests < limit then
    -- 写入当前请求
    redis.call('ZADD', key, now, now)
    -- 刷新 key 过期时间，避免冷数据常驻内存
    redis.call('PEXPIRE', key, window)
    return 1
else
    return 0
end

package main

import (
	"context"
	"time"
	"github.com/redis/go-redis/v9"
)

var slidingWindowScript = redis.NewScript(`... 上述 Lua 内容 ...`)

type RedisSlidingLimiter struct {
	client *redis.Client
	window time.Duration
	limit  int
}

func (l *RedisSlidingLimiter) Allow(ctx context.Context, key string) (bool, error) {
	now := time.Now().UnixMilli()
	windowMs := l.window.Milliseconds()

	res, err := slidingWindowScript.Run(ctx, l.client, []string{key}, now, windowMs, l.limit).Int()
	if err != nil {
		return false, err
	}
	return res == 1, nil
}