sync.Waitgroup 不被尊重

偷偷努力，悄无声息地变强，然后惊艳所有人！哈哈，小伙伴们又来学习啦~今天我将给大家介绍《sync.Waitgroup 不被尊重》，这篇文章主要会讲到等等知识点，不知道大家对其都有多少了解，下面我们就一起来看一吧！当然，非常希望大家能多多评论，给出合理的建议，我们一起学习，一起进步！

我注意到许多 goroutine 仍在运行，尽管程序应该等待它们全部完成。我的理解是添加等待组可以解决此问题，但事实并非如此。

func runintradayscanner() {
    // waitgroup for channels
    var wg sync.waitgroup

    logrus.info("clearing out pattern slices...")
    var tf5 []request.stratnotification
    var tf15 []request.stratnotification
    var tf30 []request.stratnotification
    var tf60 []request.stratnotification

    // make the channel for comms to functions
    var intradaychannel = make(chan request.stratnotification)

    // range through db table
    symbols := sources.getsymbols()
    wg.add(len(symbols))

    go func() {
        logrus.info("------waiting for workers to finish")
        wg.wait()
        logrus.info("------closing intraday channel")
        close(intradaychannel)
    }()

    for _, s := range symbols {
        // wg.add(1)
        go intradaystratify(strings.trimspace(s.symbol), intradaychannel, &wg)
        match := <-intradaychannel

        switch match.timeframe {
        case 5:
            tf5 = append(tf5, match)
        case 15:
            tf15 = append(tf15, match)
        case 30:
            tf30 = append(tf30, match)
        case 60:
            tf60 = append(tf60, match)
        default:
        }
    }

if len(tf5) > 0 {
        splitupandsendembedtodiscord(5, tf5)
    }

    if len(tf15) > 0 {
        splitupandsendembedtodiscord(15, tf15)
    }

    if len(tf30) > 0 {
        splitupandsendembedtodiscord(30, tf30)
    }

    if len(tf60) > 0 {
        splitupandsendembedtodiscord(60, tf60)
    }
}

// intradaystratify - go routine to run during market hours
func intradaystratify(ticker string, c chan request.stratnotification, wg *sync.waitgroup) {
    defer wg.done()

    candles := request.getintraday(ticker)
    for _, tf := range timeframes {
        chunkedcandles := request.determinetimeframes(tf, ticker, candles)
        if len(chunkedcandles) > 1 {
            highlows := request.calculateintradayhighlow(chunkedcandles)
            // logrus.infof("%s highlows calculated: %d", ticker, len(highlows))
            // should have more than 2 candles to start detecting patterns now
            if len(highlows) > 2 {
                bl, stratpattern := request.determinestratpattern(ticker, tf, highlows)
                if bl {
                    c <- stratpattern
                }
            }
        }

        // otherwise return an empty channel
        c <- request.stratnotification{}
    }

}

func main() {
  runintradayscanner()
}

我期望程序在 for 循环遍历符号之后再次成为单线程。相反，stdout 如下所示，看起来 goroutine 仍在返回。结果应该是每行“在时间范围内找到模式 x-x”也会有相应的“发送到不和谐”输出行。

...
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for CRM"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="SNAP Pattern 3-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for EBAY"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for MRVL"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Sending to discord: \n**SPY** :green_circle: $467.16  :red_circle: $466.92"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for CVS"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for QCOM"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Getting intraday data for ZM"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="X Pattern 3-2D found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="SQ Pattern 2D-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="MSFT Pattern 1-2U found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="NVDA Pattern 2D-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="PTON Pattern 1-2U found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="MARA Pattern 2U-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="COIN Pattern 1-2U found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="ROKU Pattern 1-2D found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="SHOP Pattern 1-2U found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="PFE Pattern 3-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="RBLX Pattern 1-2U found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="AFRM Pattern 2D-1 found for timeframe: 5!"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Sending to discord: \n**SNAP** :green_circle: $54.71  :red_circle: $54.59"
strat_1  | time="2021-11-09T20:54:57Z" level=info msg="Done with Intraday scanner"

正确答案

原始代码在每次 go 例程启动后都会阻塞，等待通过非缓冲通道发送一个值，此外，当 waitgroup 倒计时时，通道会关闭，这也关闭了接收端的通道.

恕我直言，一般规则是：

不要从接收方关闭通道，如果通道有多个并发发送方，也不要关闭通道。

package main

import (
    "fmt"
    "strings"
)

type StratNotification struct {
    Symbol string
}

func GetSymbols() []StratNotification {
    return []StratNotification{
        {Symbol: "a"},
        {Symbol: "b"},
        {Symbol: "c"},
        {Symbol: "d"},
    }
}

func RunIntradayScanner() {
    symbols := GetSymbols()
    var intradayChannel = make(chan StratNotification)
    for _, s := range symbols {
        go IntradayStratify(strings.TrimSpace(s.Symbol), intradayChannel)
    }

    for _ = range symbols {
        s := <-intradayChannel
        fmt.Println(s)
    }
}

func IntradayStratify(ticker string, c chan StratNotification) {
    // do some heavy lifting
    fmt.Println(ticker)
    c <- StratNotification{}
}

func main() {
    RunIntradayScanner()
}

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