Golang goroutine不与内部频道一起运行

发布时间：2020-12-16 19:04:02 所属栏目：大数据来源：网络整理

导读：我正在尝试实施一个字数统计程序,但第一步我遇到了一些问题. 这是我的代码： package mainimport ( "fmt" "os" "bufio" "sync")// Load data into channelfunc laodData(arr []string,channel chan string,wg sync.WaitGroup) { for _,path := range arr { f

我正在尝试实施一个字数统计程序,但第一步我遇到了一些问题.

这是我的代码：

package main

import (
    "fmt"
    "os"
    "bufio"
    "sync"
)

// Load data into channel
func laodData(arr []string,channel chan string,wg sync.WaitGroup) {
    for _,path := range arr {
        file,err := os.Open(path)
        fmt.Println("begin to laodData ",path)
        if err != nil {
            fmt.Println(err)
            os.Exit(-1)
        }
        defer file.Close()
        reader := bufio.NewReaderSize(file,32*10*1024)
        i := 0
        for {
            line,err := reader.ReadString('n')
            channel <- line
            if err != nil {
                break
            }
            i++
            if i%200 == 0 {
                fmt.Println(i," lines parsed")
            }
        }
        fmt.Println("finish laodData ",path)
    }
    wg.Done()
}

// dispatch data lines into different mappers
func dispatcher(channel chan string,wg sync.WaitGroup){
    fmt.Println("pull data 11")
    line,ok := <- channel
    fmt.Println(ok)
    for ok {
        fmt.Println(line)
        line,ok = <- channel
    }
    fmt.Println("pull data 22")
    wg.Done()
}

func main() {
    path := os.Args
    if len(path) < 2 {
        fmt.Println("Need Input Files")
        os.Exit(0)
    }
    var wg sync.WaitGroup
    wg.Add(2)

    channel := make(chan string)
    defer close(channel)

    fmt.Println("before dispatcher")
    go laodData(path[1:],channel,wg)
    go dispatcher(channel,wg)
    wg.Wait()

    fmt.Println("after dispatcher")
}

这是我的输出：

...

finish laodData  result.txt

throw: all goroutines are asleep - deadlock!

goroutine 1 [semacquire]:
sync.runtime_Semacquire(0x42154100,0x42154100)
    /usr/local/go/src/pkg/runtime/zsema_amd64.c:146 +0x25
sync.(*WaitGroup).Wait(0x4213b440,0x0)
    /usr/local/go/src/pkg/sync/waitgroup.go:79 +0xf2
main.main()
    /Users/kuankuan/go/src/mreasy/main.go:66 +0x238

goroutine 2 [syscall]:
created by runtime.main
    /usr/local/go/src/pkg/runtime/proc.c:221

goroutine 4 [chan receive]:
main.dispatcher(0x42115a50,0x0,0x2,0x0)
    /Users/kuankuan/go/src/mreasy/main.go:45 +0x223
created by main.main
    /Users/kuankuan/go/src/mreasy/main.go:65 +0x228
exit status 2

谢谢！

当main goroutine退出时程序终止,因此dispatcher()没有时间做任何事情.您需要在main()中阻塞,直到dispatcher()完成.频道可用于此：

package main

import (
    "fmt"
    "os"
    "bufio"
)

var done = make(chan bool)             // create channel

// Load files and send them into a channel for mappers reading.
func dispatcher(arr []string,channel chan string) {
    for _,err := os.Open(path)
        fmt.Println("begin to dispatch ",_ := reader.ReadString('n')
            channel <- line
            i++
            if i%200 == 0 {
                fmt.Println(i," lines parsed")
            }
        }
        fmt.Println("finish dispatch ",path)
    }
    done <- true                 // notify main() of completion
}

func main() {
    path := os.Args
    if len(path) < 2 {
        fmt.Println("Need Input Files")
        os.Exit(0)
    }
    channel := make(chan string)
    fmt.Println("before dispatcher")
    go dispatcher(path[1:],channel)
    <-done                 // wait for dispatcher()
    fmt.Println("after dispatcher")
}

（编辑：李大同）

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