Question

我是F＃的新手，我已经从我在网上找到的各种例子中明确了以下代码，试图更好地理解我如何使用它。目前，下面的代码从文件中读取机器列表并ping每台机器。我不得不将初始数组从文件分成25个机器的较小数组，以控制并发操作的数量，否则需要很长时间才能映射出机器列表。我希望能够使用线程池来管理线程，但我还没有找到让它工作的方法。任何指导都会很棒。我无法完成这项工作：

let creatework  = FileLines|> Seq.map (fun elem -> ThreadPool.QueueUserWorkItem(new WaitCallback(dowork), elem))

以下是完整的代码：

open System.Threading
open System
open System.IO

let filePath = "c:\qa\machines.txt"

let FileLines = File.ReadAllLines(filePath)

let count = FileLines.Length/25

type ProcessResult = { exitCode : int; stdout : string; stderr : string } 

let executeProcess (exe,cmdline) = 
    let psi = new System.Diagnostics.ProcessStartInfo(exe,cmdline) 
    psi.UseShellExecute <- false
    psi.RedirectStandardOutput <- true 
    psi.RedirectStandardError <- true 
    psi.CreateNoWindow <- true
    let p = System.Diagnostics.Process.Start(psi, EnableRaisingEvents = true) 
    let output = new System.Text.StringBuilder()
    let error = new System.Text.StringBuilder() 
    p.OutputDataReceived.Add(fun args -> output.AppendLine(args.Data)|> ignore) 
    p.ErrorDataReceived.Add(fun args -> error.AppendLine(args.Data) |> ignore) 
    p.BeginErrorReadLine() 
    p.BeginOutputReadLine()
    p.WaitForExit()
    { exitCode = p.ExitCode; stdout = output.ToString(); stderr = error.ToString() } 

let dowork machinename=
    async{
        let exeout = executeProcess(@"c:\windows\system32\ping.exe", "-n 1 " + machinename)
        let exelines = 
            if exeout.stdout.Contains("Reply from") then Console.WriteLine(machinename + " " + "REPLY")
            elif exeout.stdout.Contains("Request timed out.") then Console.WriteLine(machinename + " " + "RTO")
            elif exeout.stdout.Contains("Ping request could not find host") then Console.WriteLine(machinename + " " + "Unknown Host")
            else Console.WriteLine(machinename + " " + "ERROR")
        exelines
        }

printfn "%A" (System.DateTime.Now.ToString())

for i in 0..count do
    let x = i*25
    let y = if i = count then FileLines.Length-1 else (i+1)*25
    printfn "%s %d" "X equals: " x
    printfn "%s %d" "Y equals: " y
    let filesection = FileLines.[x..y]
    let creatework = filesection |> Seq.map dowork |> Async.Parallel |> Async.RunSynchronously|>ignore
    creatework

printfn "%A" (System.DateTime.Now.ToString())
printfn "finished"

更新：下面的代码可以工作，并提供了我想要做的框架。 Tomas Petricek引用的链接确实有一些代码可以使这个工作。我只需要确定哪个例子是正确的。用Java编写的重复框架在3秒内就可以了，所以我认为我正朝着正确的方向前进。我希望下面的例子对于试图在F＃中编写各种可执行文件的其他人都有用：

open System
open System.IO
open System.Diagnostics

let filePath = "c:\qa\machines.txt"

let FileLines = File.ReadAllLines(filePath)

type Process with
    static member AsyncStart psi =
        let proc = new Process(StartInfo = psi, EnableRaisingEvents = true)
        let asyncExit = Async.AwaitEvent proc.Exited
        async {
            proc.Start() |> ignore
            let! args = asyncExit
            return proc
        } 

let shellExecute(program : string, args : string) =
    let startInfo =
        new ProcessStartInfo(FileName = program, Arguments = args,
            UseShellExecute = false,
            CreateNoWindow = true,
            RedirectStandardError = true,
            RedirectStandardOutput = true)
    Process.AsyncStart(startInfo)

let dowork (machinename : string)=
    async{
        let nonbtstat = "NONE"
        use! pingout = shellExecute(@"c:\windows\system32\ping.exe", "-n 1 " + machinename)
        let pingRdToEnd = pingout.StandardOutput.ReadToEnd()
        let pingresults =
            if pingRdToEnd.ToString().Contains("Reply from") then (machinename + " " + "REPLY")
            elif pingRdToEnd.ToString().Contains("Request timed out.") then (machinename + " " + "RTO")
            elif pingRdToEnd.ToString().Contains("Ping request could not find host") then (machinename + " " + "Unknown Host")
            else (machinename + " " + "PING_ERROR")
        if pingresults.ToString().Contains("REPLY") then
            use! nbtstatout = shellExecute(@"c:\windows\system32\nbtstat.exe", "-a " + machinename)
            let nbtstatRdToEnd = nbtstatout.StandardOutput.ReadToEnd().Split('\n')
            let nbtstatline = Array.tryFind(fun elem -> elem.ToString().Contains("<00>  UNIQUE      Registered")) nbtstatRdToEnd
            return Console.WriteLine(pingresults + nbtstatline.Value.ToString())
        else return Console.WriteLine(pingresults + " " + nonbtstat)
        }

printfn "%A" (System.DateTime.Now.ToString())

let creatework = FileLines |> Seq.map dowork |> Async.Parallel |> Async.RunSynchronously|>ignore
creatework

printfn "%A" (System.DateTime.Now.ToString())
printfn "finished"

Answer 1

代码的主要问题是executeProcess是一个需要很长时间才能运行的同步函数（它运行ping.exe进程并等待其结果）。一般规则是线程池中的任务不应该长时间阻塞（因为它们会阻塞线程池线程，这意味着线程池无法有效地安排其他工作）。

我认为你可以通过使executeProcess异步来轻松解决这个问题。您可以使用WaitForExit等待Exitted事件，而不是调用Async.AwaitEvent（哪些阻止）：

let executeProcess (exe,cmdline) = async {
    let psi = new System.Diagnostics.ProcessStartInfo(exe,cmdline)  
    psi.UseShellExecute <- false 
    // [Lots of stuff omitted]
    p.BeginOutputReadLine() 
    let! _ = Async.AwaitEvent p.Exited
    return { exitCode = p.ExitCode
             stdout = output.ToString(); stderr = error.ToString() } }

这应该取消阻塞线程池中的线程，这样您就可以在输入数组的所有URL上使用Async.Parallel，而无需任何手动调度。

编辑正如@desco在评论中指出的那样，如果进程在到达AwaitEvent行之前退出（在它可能错过事件之前），则上述情况并不完全正确。要解决这个问题，您需要使用Event.guard函数，该问题已在此SO问题中讨论过：

Need help regarding Async and fsi

F＃ - 需要帮助将其转换为使用线程池

1 个答案: