Go Channel Practice III - Leaky Bucket

https://en.wikipedia.org/wiki/Leaky_bucket

实现自己的 Leaky Bucket，首先定义 struct。

type LeakyBucket struct {
	Quota  int 
	Remain int
	ticker *time.Ticker
	quit   chan bool
	mutex  sync.Mutex
}

ticker 用来每一个时间段来做什么东西，quit 是用来 close 相应的 channel，mutex 是为了避免竞争，给资源加锁。

实现一个 LB

func New(quota int) *LeakyBucket {
	ticker := time.NewTicker(time.Second)
	lb := &LeakyBucket{
		Quota:  quota,
		Remain: quota,
		ticker: ticker,
		quit:   make(chan bool),
	}
	go func() {
		for {
			select {
			case <-ticker.C:
				fmt.Println("tick")
				lb.mutex.Lock()
				lb.Remain = lb.Quota
				lb.mutex.Unlock()
			case <-lb.quit:
				return
			}
		}
	}()

	return lb
}

实现一个 LeakyBucket 的函数，来关闭 ticker 和 New 出来的 goroutine。

func (l *LeakyBucket) Close() {
	l.ticker.Stop()
	l.quit <- true
}

每次 Leak 的时候，首先判断 remain 的数目是否大于输入。如果小于输入，失败返回；如果大于等于，则 remain 减去输入。

func (l *LeakyBucket) Leak(count int) bool {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	if l.Remain < count {
		fmt.Println("leak failed")
		return false
	}
	l.Remain -= count
	fmt.Println("leak success")
	return true
}

整体实现

package main

import (
	"fmt"
	"sync"
	"time"
)

type LeakyBucket struct {
	Quota  int 
	Remain int
	ticker *time.Ticker
	quit   chan bool
	mutex  sync.Mutex
}

func New(quota int) *LeakyBucket {
	ticker := time.NewTicker(time.Second)
	lb := &LeakyBucket{
		Quota:  quota,
		Remain: quota,
		ticker: ticker,
		quit:   make(chan bool),
	}
	go func() {
		for {
			select {
			case <-ticker.C:
				fmt.Println("tick")
				lb.mutex.Lock()
				lb.Remain = lb.Quota
				lb.mutex.Unlock()
			case <-lb.quit:
				return
			}
		}
	}()

	return lb
}

func (l *LeakyBucket) Close() {
	l.ticker.Stop()
	l.quit <- true
}

func main() {
	lb := New(1000)
	fmt.Println(lb.Leak(500))
	fmt.Println(lb.Leak(800))
	time.Sleep(time.Millisecond * 1100)
	fmt.Println(lb.Leak(800))
}

func (l *LeakyBucket) Leak(count int) bool {
	l.mutex.Lock()
	defer l.mutex.Unlock()
	if l.Remain < count {
		fmt.Println("leak failed")
		return false
	}
	l.Remain -= count
	fmt.Println("leak success")
	return true
}

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