golang中管道热替换

golang中管道替换问题

https://blog.csdn.net/cyk2396/article/details/78875347

1.运行以下代码：

var chan1 chan int

var chanLength int = 18

var interval time.Duration = 1500 * time.Millisecond

//var interval2 time.Duration = 1800 * time.Millisecond

//golang在替换通道时引起的问题

func main() {

chan1 = make(chan int, chanLength)

//该goroutine是每隔1.5秒向chan1中发送一个元素，

//当满足条件时，重置chan1,此时chan1会指向一个新通道

go func() {

for i := 0; i < chanLength; i++ {

if i > 0 && i%3 == 0 {

fmt.Println("chan1 reset")

chan1 = make(chan int, chanLength)

}

fmt.Println("send an value : ", i)

chan1 <- i

time.Sleep(interval)

}

fmt.Println("close chan1")

close(chan1)

}()

//用于接收chan1中的元素
receive(chan1)

}

func receive(chan2 chan int) {

fmt.Println("start receive value from chan1 ...")

timer := time.After(30 * time.Second)

Loop:

for {

select {

case e, ok := <-chan2:

if !ok {

fmt.Println("chan1 has closed ...")

break Loop

}

		fmt.Println("receive value : ", e)
		time.Sleep(interval)
	case <-timer:
		fmt.Println("time out")
		break Loop
	}
}

}

结果如下：

start receive value from chan1 ...

send an value : 0

receive value : 0

send an value : 1

receive value : 1

send an value : 2

receive value : 2

chan1 reset

send an value : 3

send an value : 4

send an value : 5

chan1 reset

send an value : 6

send an value : 7

send an value : 8

chan1 reset

send an value : 9

send an value : 10

send an value : 11

chan1 reset

send an value : 12

send an value : 13

send an value : 14

chan1 reset

send an value : 15

send an value : 16

send an value : 17

close chan1

time out

引起这个的原因是：对变量的重新赋值操作是无法被传递的。在上面这个demo中，当chan1指向了新管道时，receive()函数还是调用原来的旧管道。

解决办法是:通过函数调用每次都获取最新的管道。代码如下：

var chan1 chan int

var chanLength int = 18

var interval time.Duration = 1500 * time.Millisecond

var interval2 time.Duration = 1550 * time.Millisecond

//golang在替换通道时引起的问题

func main() {

chan1 = make(chan int, chanLength)

//该goroutine是每隔1.5秒向chan1中发送一个元素，

//当满足条件时，重置chan1,此时chan1会指向一个新通道

go func() {

for i := 0; i < chanLength; i++ {

if i > 0 && i%3 == 0 {

fmt.Println("chan1 reset")

chan1 = make(chan int, chanLength)

}

fmt.Println("send an value : ", i)

chan1 <- i

time.Sleep(interval)

}

fmt.Println("close chan1")

close(chan1)

}()

//用于接收chan1中的元素
receive()

}

func receive() {

fmt.Println("start receive value from chan1 ...")

timer := time.After(30 * time.Second)

Loop:

for {

select {

case e, ok := <-getChan(): //通过getChan()每次都获取最新的管道

if !ok {

fmt.Println("chan1 has closed ...")

break Loop

}

		fmt.Println("receive value : ", e)
		time.Sleep(interval2) // 时间间隔相比发送方的时间间隔增加50ms，为了在getChan()时能获取最新的chan
	case <-timer:
		fmt.Println("time out")
		break Loop
	}
}

}

//获取管道chan1

func getChan() chan int {

return chan1

}