douhang1913
2018-07-08 10:46 阅读 36
已采纳

监控golang中的频道充值

There are several channels to monitor, their type are different and irrelevant(since we only care about len and cap), but golang compiler does not accept following code, whatever T is:

func monitorChan(ch chan T) {
    for {
        if len(ch) == cap(ch) {
            log.Warn("log")
        }
        time.Sleep(chanMonitorInterval)
    }
}

it shows error:

cannot use ch (type chan []byte) as type chan interface {} in argument to monitorChan.

How can this function be modified to write once monitor every channel?


Here is my code:

package main

import (
    "fmt"
    "time"
)

func monitorChan(ch chan interface{}) {
    for {
        if len(ch) == cap(ch) {
            fmt.Println("log")
        }
        time.Sleep(1 * time.Second)
    }
}

func main() {
    ch := make(chan []byte, 100)
    go monitorChan(ch)
    // actual things below ...
}

Playground: https://play.golang.org/p/t7T28IpLNAs

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2条回答 默认 最新

  • 已采纳
    dongliushui2001 dongliushui2001 2018-07-08 14:44

    Use reflection. For example,

    package main
    
    import (
        "log"
        "reflect"
        "time"
    )
    
    func monitorChan(ch interface{}, intvl time.Duration) {
        v := reflect.ValueOf(ch)
        if v.Kind() != reflect.Chan {
            return
        }
    
        c := v.Cap()
        if c == 0 {
            return
        }
        for {
            if l := v.Len(); l == c {
                log.Printf("log: len(%d) cap(%d)", l, c)
            }
            time.Sleep(intvl)
        }
    }
    
    func main() {
        log.Print("main")
        c := make(chan []byte, 10)
        var chanMonitorInterval = 1 * time.Second
        go monitorChan(c, chanMonitorInterval)
        log.Print("monitor")
    
        time.Sleep(5 * chanMonitorInterval)
        for len(c) != cap(c) {
            c <- []byte{}
        }
        log.Print("len(c) == cap(c)")
        time.Sleep(3 * chanMonitorInterval)
        <-c
        log.Print("len(c) < cap(c)")
        time.Sleep(5 * chanMonitorInterval)
        log.Print("main")
    }
    

    Playground: https://play.golang.org/p/c5VhIIO0pik

    Output:

    2009/11/10 23:00:00 main
    2009/11/10 23:00:00 monitor
    2009/11/10 23:00:05 len(c) == cap(c)
    2009/11/10 23:00:06 log: len(10) cap(10)
    2009/11/10 23:00:07 log: len(10) cap(10)
    2009/11/10 23:00:08 log: len(10) cap(10)
    2009/11/10 23:00:08 len(c) < cap(c)
    2009/11/10 23:00:13 main
    

    References:

    Package reflect

    The Go Blog: The Laws of Reflection

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  • drb0901500211 drb0901500211 2018-07-08 11:35

    Create an interface{} type channel and pass any type wrapping around interface{}, then fetch the use type assert on receiving end.

    package main
    
    import (
        "fmt"
        "sync"
    )
    
    var wg sync.WaitGroup
    
    func monitorChan(ch chan interface{}) {
        val := <-ch
        fmt.Println(string(val.(interface{}).([]uint8)))
        wg.Done()
    }
    
    func main() {
        ch := make(chan interface{}, 100)
        wg.Add(1)
        ch <- []byte("hello")
        go monitorChan(ch)
        wg.Wait()
        // actual things below ...
    }
    

    Working code on Go Playground

    Edited :- you can also go for reflect package to get the values of channels after wrapping the channels inside interface{}

    package main
    
    import (
        "fmt"
        "sync"
        "reflect"
    )
    
    var wg sync.WaitGroup
    
    func monitorChan(i interface{}) {
        defer wg.Done()
        v := reflect.ValueOf(i)
        fmt.Printf("%s size: %d/%d
    ", v.Kind(), v.Len(), v.Cap())
    }
    
    func main() {
        ch := make(chan []byte, 100)
        wg.Add(1)
        go monitorChan(ch)
        wg.Wait()
        // actual things below ...
    }
    

    Playground example

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