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Question

我有一个 PowerShell 脚本，我想在其中创建一个后台线程并与我的主线程动态交换数据。这个想法是使用信息流，因为它可以轻松处理各种对象。

通常我会像下面这样将 PowerShell 对象赋予自身：

$Code =
{
    Param($Me)
    #Here I can use $Me.Streams.Information to exchange data any time,
    #for example to feed my thread with more work to do on the fly

    $ResultData = [System.Object[]]::new(0)
    $WorkCounter = 0
    $Finished = $false
    while (-not $Finished)
    {
        while ($Me.Streams.Information.Count -eq $WorkCounter)
        {
            #Wait for data to be added to the information stream
            Sleep -MilliSeconds 10
        }

        $InputData = $Me.Streams.Information[-1].MessageData
        if ($InputData -eq "FINISHED")
        {
            $Finished = $true
        }
        else
        {
            <# Do some stuff with the $InputData #>
            $ResultData += $ProgressedInputData

        }
        $WorkCounter++
    }
    Write-Information $ResultData
}
$PS = [PowerShell]::Create()
$PS.AddScript($Code) | Out-Null
$PS.AddArgument($PS) | Out-Null #Hand the PS to itself to make the streams accessible inside the thread
$Handle = $PS.BeginInvoke() | Out-Null

for ($i = 0; $i -lt 10; $i++)
{
    $PS.Streams.Information.Add([System.Management.Automation.InformationRecord]::new($i, ""))
    #I just gave my background thread some stuff to do without the need to instantiate a new one again
    #Now this thread can do some work too...
}
$PS.Streams.Information.Add([System.Management.Automation.InformationRecord]::new("FINISHED", ""))
$Handle.AsyncWaitHandle.WaitOne() #Wait for my background thread to finish all its work
$SomeReturnValue = $PS.Streams.Information[-1].MessageData

我的实际问题是：是否有可能访问当前的 PowerShell 实例而无需像我对 $PS.AddArgument($PS)?

Answer 1

您不需要滥用 PowerShell.Streams 进行 two-way 通信 - PowerShell 已经有一个在两个运行空间之间桥接会话状态的工具，一个 so-called 会话状态代理！

让我们从稍微重写您的 $code 块开始：

$code = {
  while($config['Enabled']){
    $inputData = $null
    if($queue.TryDequeue([ref]$inputData)) {
      #process input data
      Write-Information $inputData
    }
    else {
      Start-Sleep -Milliseconds 50
    }
  }
}

请注意，我使用了两个变量，$config 和 $queue，尽管我实际上没有参数化或以其他方式定义它们，但我们仍在使用信息流进行通信输出（你也可以使用标准输出）。

现在我们只需要创建两个可以绑定到这些变量的对象。对于 thread-safety，我们将使用：

A ConcurrentQueue[psobject] 输入数据
A thread-synchronized [hashtable] 配置数据

# Create PowerShell instance like before
$PS = [powershell]::Create()

# Create the thread-safe collections we'll be using to communicate
$queue = [System.Collections.Concurrent.ConcurrentQueue[psobject]]::new()
$config = [hashtable]::Synchronized(@{
  Enabled = $true
})

# Now make those variable references available in the runspace where the backgroun code will be running
$ps.Runspace.SessionStateProxy.PSVariable.Set('queue', $queue)
$ps.Runspace.SessionStateProxy.PSVariable.Set('config', $config)

有了用于交换输入和配置数据的工具，您现在可以调用后台作业并根据通过 $queue 提供的输入观察它的行为（我强烈建议将以下语句输入到交互式提示，稍微玩一下):

# Invoke background code
$asyncHandle = $PS.BeginInvoke()

# Try adding some data to the queue
$queue.TryAdd([pscustomobject]@{ Property = "Value 123"})

# Wait for a bit
Start-Sleep -Milliseconds 100

# Observe that the queue has been emptied by the background code
Write-Host "Queue is empty: $($queue.IsEmpty)"

# Observe that the background code actually processed (and output) the data
$ps.Streams.Information

Answer 2

让我提供 , based on the ThreadJob module's Start-ThreadJob cmdlet, which ships with PowerShell (Core) v6+ 的替代方案，在 Windows PowerShell 中可以按需安装（例如，Install-Module ThreadJob -Scope CurrentUser）

顾名思义，它提供基于线程的后台操作，作为 child-process 的更快 lighter-weight 替代方案 由 Start-Job (see 为并列创建的基于的后台作业。

因此，它更友好，higher-level 替代通过 PowerShell SDK 管理多线程（运行空间），允许您使用常用的 job-management cmdlet 与后台线程交互。

一个简单的例子：

# Create a synchronized (thread-safe) queue.
$threadSafeQueue = [System.Collections.Concurrent.ConcurrentQueue[string]]::new()

# Start a thread job that keeps processing elements in the queue
# indefinitely, sleeping a little between checks for new elements.
# A special element value is used to signal that processing should end.
$jb = Start-ThreadJob {
  $q = $using:threadSafeQueue # get a reference to the thread-safe queue.
  $element = $null # variable to receive queue elements
  while ($true) {
    # Process all elements currently in the queue.
    while ($q.TryDequeue([ref] $element)) {
      # Check for the signal to quit, by convention a single NUL char. here.
      if ("`0" -eq $element) { 'Quitting...'; return }
      # Process the element at hand.
      # In this example, echo the dequeued element enclosed in "[...]"
      '[{0}]' -f $element
    }
    # Queue is (now) empty, sleep a little before checking for new elements.
    Start-Sleep -MilliSeconds 100
  }
}

# Populate the queue with the numbers from 1 to 10.
1..10 | ForEach-Object {
  $threadSafeQueue.Enqueue($_) # This triggers activity in the background thread.
  # Retrieve available output from the thread job.
  $jb | Receive-Job
}

# Send the quit signal, retrieve remaining output and delete the job.
$threadSafeQueue.Enqueue("`0")
$jb | Receive-Job -Wait -AutoRemoveJob

输出：

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
Quitting...

另请参阅：

PowerShell (Core) v7+ Foreach-Object -Parallel 功能，它同样使用线程并行处理 管道输入 。

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