package main

import (
	"fmt"
	"sync"
)

func main() {
	count := 10 // 最大支持并發(fā)
	sum := 100 // 任務(wù)總數(shù)
	wg := sync.WaitGroup{} //控制主協(xié)程等待所有子協(xié)程執(zhí)行完之后再退出。

	c := make(chan struct{}, count) // 控制任務(wù)并發(fā)的chan
	defer close(c)

	for i:=0; i<sum;i++{
		wg.Add(1)
		c <- struct{}{} // 作用類似于waitgroup.Add(1)
		go func(j int) {
			defer wg.Done()
			fmt.Println(j)
			<- c // 執(zhí)行完畢，釋放資源
		}(i)
	}
	wg.Wait()
}

package main

import (
	"fmt"
	"sync"
)

func main() {
	count := 10 // 最大支持并發(fā)
	sum := 100 // 任務(wù)總數(shù)
	wg := sync.WaitGroup{} //控制主協(xié)程等待所有子協(xié)程執(zhí)行完之后再退出。

	c := make(chan struct{}, count) // 控制任務(wù)并發(fā)的chan
	defer close(c)

	for i:=0; i<sum;i++{
		wg.Add(1)
		go func(j int) {
			defer wg.Done()
			c <- struct{}{} // 作用類似于waitgroup.Add(1)
			fmt.Println(j)
		}(i)
		<- c // 執(zhí)行完畢，釋放資源
	}
	wg.Wait()
}

package main

import (
	"log"
	"time"

	"github.com/Jeffail/tunny"
)

func main() {
	pool := tunny.NewFunc(10, func(i interface{}) interface{} {
		log.Println(i)
		time.Sleep(time.Second)
		return nil
	})
	defer pool.Close()

	for i := 0; i < 500; i++ {
		go pool.Process(i)
	}
	time.Sleep(time.Second * 4)
}

func main() {
	var wg sync.WaitGroup
	for i := 0; i < math.MaxInt32; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			fmt.Println(i)
			time.Sleep(time.Second)
		}(i)
	}
	wg.Wait()
}

package util
 
import (
	"sync"
)
 
type concurrencyLimiter struct {
	runningNum  int32
	limit       int32
	blockingNum int32
	cond        *sync.Cond
	mu          *sync.Mutex
}
 
// NewConcurrencyLimiter 創(chuàng)建一個(gè)并發(fā)限制器，limit為并發(fā)限制數(shù)量，可通過(guò) Reset() 動(dòng)態(tài)調(diào)整limit。
// 每次調(diào)用 Get() 來(lái)獲取一個(gè)資源，然后創(chuàng)建一個(gè)協(xié)程，完成任務(wù)后通過(guò) Release() 釋放資源。
func NewConcurrencyLimiter(limit int32) *concurrencyLimiter {
	l := new(sync.Mutex)
	return &concurrencyLimiter{
		limit: limit,
		cond:  sync.NewCond(l),
		mu:    l,
	}
}
 
// Reset 可更新limit，需要保證limit > 0
func (c *concurrencyLimiter) Reset(limit int32) {
	c.mu.Lock()
	defer c.mu.Unlock()
 
	tmp := c.limit
	c.limit = limit
	blockingNum := c.blockingNum
	// 優(yōu)先喚醒阻塞的任務(wù)
	if limit-tmp > 0 && blockingNum > 0 {
		for i := int32(0); i < limit-tmp && blockingNum > 0; i++ {
			c.cond.Signal()
			blockingNum--
		}
	}
}
 
// Get 當(dāng) concurrencyLimiter 沒(méi)有資源時(shí)，會(huì)阻塞。
func (c *concurrencyLimiter) Get() {
	c.mu.Lock()
	defer c.mu.Unlock()
 
	if c.runningNum < c.limit {
		c.runningNum++
		return
	}
	c.blockingNum++
	for !(c.runningNum < c.limit) {
		c.cond.Wait()
	}
	c.runningNum++
	c.blockingNum--
}
 
// Release 釋放一個(gè)資源
func (c *concurrencyLimiter) Release() {
	c.mu.Lock()
	defer c.mu.Unlock()
 
	if c.blockingNum > 0 {
		c.runningNum--
		c.cond.Signal()
		return
	}
 
	c.runningNum--
}