go - 多次运行相同的go程序会引发 panic : send on closed channel

Question

我刚接触golang并试图了解workerpool的工作原理。如果我运行一次，并且如果尝试运行多次，以下示例程序将运行良好，并且出现紧急情况:在关闭 channel 上发送错误。 Go版本是go1.14.2

package main
import (
    "fmt"
    "time"
)
func main() {
    jobs := make(chan int, 10)
    results := make(chan int, 10)

    for x := 1; x <= 3; x++ {
        go worker(x, jobs, results)
    }

    for j := 1; j <= 6; j++ {
        jobs <- j
    }
    close(jobs)
    for r:=range results{
        fmt.Println("Result received from worker: ", r)
    }
}
func worker(ID int, jobs <-chan int, results chan<- int) {
    for job := range jobs {
        fmt.Println("Worker ", ID, " is working on job ", job)
        time.Sleep(1000*time.Millisecond)
        fmt.Println("Worker ", ID, " completed work on job ", job)
        results <- job
    }
    close(results)
}

第一次运行可以

go run main.go                                                                            
Worker  3  is working on job  1
Worker  1  is working on job  2
Worker  2  is working on job  3
Worker  2  completed work on job  3
Worker  2  is working on job  4
Result received from worker:  3
Worker  1  completed work on job  2
Worker  1  is working on job  5
Result received from worker:  2
Worker  3  completed work on job  1
Worker  3  is working on job  6
Result received from worker:  1
Worker  3  completed work on job  6
Result received from worker:  6

第二次运行给出了这一点。

Worker  3  is working on job  2
Worker  2  is working on job  3
Worker  1  is working on job  1
Worker  3  completed work on job  2
Worker  3  is working on job  4
Worker  2  completed work on job  3
Worker  2  is working on job  5
Worker  1  completed work on job  1
Worker  1  is working on job  6
Result received from worker:  2
Result received from worker:  3
Result received from worker:  1
Worker  1  completed work on job  6
Worker  3  completed work on job  4
Result received from worker:  6
panic: send on closed channel

goroutine 35 [running]:
main.worker(0x3, 0xc0000b0000, 0xc0000b00b0)
    /home/jibi_makkar/code/go/src/main.go:30 +0x252
created by main.main
    /home/jibi_makkar/code/go/src/main.go:13 +0xad
exit status 2

谁能帮助我了解发生了什么事？

Answer 1

您有多个goroutines关闭results channel 。

func worker(ID int, jobs <-chan int, results chan<- int) {
    for job := range jobs {
        fmt.Println("Worker ", ID, " is working on job ", job)
        time.Sleep(1000*time.Millisecond)
        fmt.Println("Worker ", ID, " completed work on job ", job)
        results <- job
    }
    close(results)            <<<<-------- Here
}

您可以在三个不同的并行goroutine中运行此 worker函数。第一个到达标记行的 channel 关闭，其他 channel 尝试在循环中的 results <- job中发送已关闭的 channel 。