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目录
1、ants介绍
2、使用方式汇总
3、各种使用方式详解
3.1 默认池
3.2 普通模式
3.3 带参函数
3.4 多池多协程
4、总结
1、ants介绍
众所周知，goroutine相比于线程来说，更加轻量、资源占用更少、无线程上下文切换等优势，但是也不能无节制的创建使用，如果系统中开启的goroutine过多而没有及时回收，也会造成系统内存资源耗尽。
ants是一款高性能的协程管理池，实现了协程的创建、缓存、复用、刷新、停止能功能，同时允许开发者设置线程池中worker的数量、线程池本身的个数以及workder中的任务，从而实现更加高效的运行效果。
github：GitHub - panjf2000/ants: 🐜🐜🐜 ants is a high-performance and low-cost goroutine pool in Go./ ants 是一个高性能且低损耗的 goroutine 池。
2、使用方式汇总
ants的使用有四种方式，分别如下：
这四种使用方式，前两种最常用，基本能满足日常系统的开发需要，第四种默认池，简单的场景也可以用，但不推荐，多池的情况还没想到特别合适的应用场景。
3、各种使用方式详解
3.1 默认池
ants在启动时，会默认初始化一个协程池，这部分代码位于ants.go文件中：
var (// ErrLackPoolFunc will be returned when invokers don't provide function for pool.ErrLackPoolFunc = errors.New("must provide function for pool")// ErrInvalidPoolExpiry will be returned when setting a negative number as the periodic duration to purge goroutines.ErrInvalidPoolExpiry = errors.New("invalid expiry for pool")// ErrPoolClosed will be returned when submitting task to a closed pool.ErrPoolClosed = errors.New("this pool has been closed")// ErrPoolOverload will be returned when the pool is full and no workers available.ErrPoolOverload = errors.New("too many goroutines blocked on submit or Nonblocking is set")// ErrInvalidPreAllocSize will be returned when trying to set up a negative capacity under PreAlloc mode.ErrInvalidPreAllocSize = errors.New("can not set up a negative capacity under PreAlloc mode")// ErrTimeout will be returned after the operations timed out.ErrTimeout = errors.New("operation timed out")// ErrInvalidPoolIndex will be returned when trying to retrieve a pool with an invalid index.ErrInvalidPoolIndex = errors.New("invalid pool index")// ErrInvalidLoadBalancingStrategy will be returned when trying to create a MultiPool with an invalid load-balancing strategy.ErrInvalidLoadBalancingStrategy = errors.New("invalid load-balancing strategy")// workerChanCap determines whether the channel of a worker should be a buffered channel// to get the best performance. Inspired by fasthttp at// https://github.com/valyala/fasthttp/blob/master/workerpool.go#L139workerChanCap = func() int {// Use blocking channel if GOMAXPROCS=1.// This switches context from sender to receiver immediately,// which results in higher performance (under go1.5 at least).if runtime.GOMAXPROCS(0) == 1 {return 0}// Use non-blocking workerChan if GOMAXPROCS>1,// since otherwise the sender might be dragged down if the receiver is CPU-bound.return 1}()// log.Lmsgprefix is not available in go1.13, just make an identical value for it.logLmsgprefix = 64defaultLogger = Logger(log.New(os.Stderr, "[ants]: ", log.LstdFlags|logLmsgprefix|log.Lmicroseconds))// Init an instance pool when importing ants.defaultAntsPool, _ = NewPool(DefaultAntsPoolSize)
)使用起来就比较简单了，直接往池子里提交任务即可。
package mainimport ("fmt""sync""time""github.com/panjf2000/ants/v2"
)func add(d int) {sum := 0for i := 0; i < d; i++ {sum += i}
}
func main() {var wg sync.WaitGroupnow := time.Now()for i := 0; i < 5; i++ {wg.Add(1)ants.Submit(func() {add(10000000000)wg.Done()})}wg.Wait()fmt.Println(time.Since(now))now = time.Now()for i := 0; i < 5; i++ {add(10000000000)}fmt.Println(time.Since(now))
}
运行结果：
3.2 普通模式
普通模式和使用默认池非常类似，但是需要自己创建一个线程池：
p, _ := ants.NewPool(5)函数参数为协程池协程个数，测试代码如下：
package mainimport ("fmt""sync""time""github.com/panjf2000/ants/v2"
)func add(d int) {sum := 0for i := 0; i < d; i++ {sum += i}
}
func main() {var wg sync.WaitGroupnow := time.Now()p, _ := ants.NewPool(5)for i := 0; i < 5; i++ {wg.Add(1)p.Submit(func() {add(10000000000)wg.Done()})}wg.Wait()fmt.Println("协程池运行：", time.Since(now))now = time.Now()for i := 0; i < 5; i++ {add(10000000000)}fmt.Println("循环运行：", time.Since(now))
}
3.3 带参函数
带参函数，重点是往worker中传递函数执行的参数，每个workder中都是同一个执行函数。
package mainimport ("fmt""sync""time""github.com/panjf2000/ants/v2"
)func add(d int) {sum := 0for i := 0; i < d; i++ {sum += i}fmt.Println("the sum is: ", sum)
}
func main() {var wg sync.WaitGroupnow := time.Now()p, _ := ants.NewPoolWithFunc(5, func(i interface{}) {add(i.(int))wg.Done()})for i := 0; i < 5; i++ {wg.Add(1)p.Invoke(1000000000)}wg.Wait()fmt.Println("循环运行：", time.Since(now))
}
运行结果：
liupeng@liupengdeMacBook-Pro ants_study % go run thread_default.go
the sum is: 499999999500000000
the sum is: 499999999500000000
the sum is: 499999999500000000
the sum is: 499999999500000000
the sum is: 499999999500000000
循环运行： 352.447333ms3.4 多池多协程
这种模式，就是声明了多个协程池，每个池子里有多个协程在跑。
package mainimport ("fmt""sync""time""github.com/panjf2000/ants/v2"
)func add(d int) {sum := 0for i := 0; i < d; i++ {sum += i}fmt.Println("the sum is: ", sum)
}
func main() {var wg sync.WaitGrouprunTimes := 20now := time.Now()mpf, _ := ants.NewMultiPoolWithFunc(10, runTimes/10, func(i interface{}) {add(i.(int))wg.Done()}, ants.LeastTasks)for i := 0; i < runTimes; i++ {wg.Add(1)mpf.Invoke(1000000000)}wg.Wait()fmt.Println("循环运行：", time.Since(now))
}
运行记录：
4、总结
以上就是ants协程池所有的使用方式，3.2、3.3章节介绍的两种方式比较常用，也是推荐的使用方式，使用协程池，可以有效的控制系统硬件资源的使用，防止机器被打满，对于高并发服务非常推荐使用。
后面会学习一下ants的源码，并整理成文档发出来，欢迎围观。