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本文为 应对突防流量 系列文章，以下为相关基友篇
计数器限流
package main
import (
"fmt"
"sync"
"time"
)
type RequestLimiter struct {
Interval time.Duration // 重新计数时间
MaxCount int // 最大计数
Lock sync.Mutex
ReqCount int // 目前的请求数
}
func (reqLimiter *RequestLimiter) IsAvailable() bool {
reqLimiter.Lock.Lock()
defer reqLimiter.Lock.Unlock()
return reqLimiter.ReqCount < reqLimiter.MaxCount
}
// 非阻塞
func (reqLimiter *RequestLimiter) AddRequestCount() bool {
reqLimiter.Lock.Lock()
defer reqLimiter.Lock.Unlock()
if reqLimiter.ReqCount < reqLimiter.MaxCount {
reqLimiter.ReqCount += 1
return true
}
return false
}
func NewRequestLimitService(interval time.Duration, maxCount int) *RequestLimiter {
reqLimit := &RequestLimiter{
Interval: interval,
MaxCount: maxCount,
}
go func() {
ticker := time.NewTicker(interval)
for true {
<-ticker.C
reqLimit.Lock.Lock()
fmt.Println("reset Count ...")
reqLimit.ReqCount = 0
reqLimit.Lock.Unlock()
}
}()
return reqLimit
}
/**
原理：协程不阻塞 + 死循环 + ticker 定时执行 ReqCount 归零
ticker := time.NewTicker(2*time.Second)
for {
currentTime := <-ticker.C
fmt.Println("当前时间为:", currentTime)
}
输出：
当前时间为: 2021-05-19 11:02:12.3603475 +0800 CST m=+2.002147201
当前时间为: 2021-05-19 11:02:14.3611806 +0800 CST m=+4.002980301
当前时间为: 2021-05-19 11:02:16.360625 +0800 CST m=+6.002424701
*/
func main() {
service := NewRequestLimitService(time.Second, 2)
for true {
hasToken := service.AddRequestCount()
if hasToken {
fmt.Println(time.Now())
}
}
}
滑动窗口
package main
import (
"fmt"
"sync"
"time"
)
type WindowLimiter struct {
Interval time.Duration // 总计数时间
WinCount []int // 每个窗口的访问数量
TicketSize int // 窗口最大容量
TicketCount int // 窗口数量
Lock sync.Mutex
CurIndex int // 目前使用哪个窗口
}
func (reqLimiter *WindowLimiter) IsAvailable() bool {
reqLimiter.Lock.Lock()
defer reqLimiter.Lock.Unlock()
return reqLimiter.WinCount[reqLimiter.CurIndex] < reqLimiter.TicketSize
}
func (reqLimiter *WindowLimiter) AddRequestCount() bool {
reqLimiter.Lock.Lock()
defer reqLimiter.Lock.Unlock()
if reqLimiter.WinCount[reqLimiter.CurIndex] < reqLimiter.TicketSize {
reqLimiter.WinCount[reqLimiter.CurIndex]++
return true
}
return false
}
func NewRequestLimitService(interval time.Duration, ticketCount int, ticketSize int) *WindowLimiter {
reqLimit := &WindowLimiter{
Interval: interval,
WinCount: make([]int, ticketCount, ticketCount),
TicketSize: ticketSize,
TicketCount: ticketCount,
CurIndex: 0,
}
go func() {
ticker := time.NewTicker(time.Duration(interval.Nanoseconds() / int64(ticketCount)))
for true {
<-ticker.C
reqLimit.Lock.Lock()
reqLimit.CurIndex = (reqLimit.CurIndex + 1) % reqLimit.TicketCount
reqLimit.WinCount[reqLimit.CurIndex] = 0
fmt.Println("reset Count ...")
reqLimit.Lock.Unlock()
}
}()
return reqLimit
}
func main() {
service := NewRequestLimitService(time.Second, 2, 1)
for true {
hasToken := service.AddRequestCount()
if hasToken {
fmt.Println(time.Now())
}
}
}
漏桶算法
package main
import (
"fmt"
"math"
"sync"
"time"
)
type BucketLimiter struct {
Timestamp time.Time // 当前注水的时间戳
Capacity float64 // 桶的容量
Rate float64 // 速度
Water float64 // 当前水量
Lock sync.Mutex
}
func AddWater(bucket *BucketLimiter) bool {
now := time.Now()
leftWater := math.Max(0, bucket.Water-now.Sub(bucket.Timestamp).Seconds()*bucket.Rate)
bucket.Lock.Lock()
defer bucket.Lock.Unlock()
if leftWater+1 < bucket.Capacity {
// 尝试加水，此时水桶未满
bucket.Timestamp = now
bucket.Water = leftWater + 1
return true
} else {
// 水满了，拒绝访问
return false
}
}
func main() {
service := &BucketLimiter{
Timestamp: time.Now(),
Capacity: 2,
Rate: 1,
Water: 0,
}
for true {
hasToken := AddWater(service)
if hasToken {
fmt.Println(time.Now())
}
}
}
令牌桶算法
package main
import (
"math"
"sync"
"time"
)
// 定义令牌桶结构
type tokenBucket struct {
timestamp time.Time // 当前时间戳
capacity float64 // 桶的容量（存放令牌的最大量）
rate float64 // 令牌放入速度
tokens float64 // 当前令牌总量
lock sync.Mutex
}
// 判断是否获取令牌（若能获取，则处理请求）
func getToken(bucket tokenBucket) bool {
now := time.Now()
bucket.lock.Lock()
defer bucket.lock.Unlock()
// 先添加令牌
leftTokens := math.Max(bucket.capacity, bucket.tokens+now.Sub(bucket.timestamp).Seconds()*bucket.rate)
if leftTokens < 1 {
// 若桶中一个令牌都没有了，则拒绝
return false
} else {
// 桶中还有令牌，领取令牌
bucket.tokens -= 1
bucket.timestamp = now
return true
}
}
