我如何才能创建在完成时产生结果的工作？

html5 • • 问答

问题

考虑你有 4 台机器。

  • 机器A很慢
  • 机器B是中速，
  • 机器C很快。
  • LocalHost 是超快的。

在每台远程机器上，您想对前 100 万个素数求和。您可以从本地主机执行此操作：

$servers = @("MachineA","MachineB","MachineC")
Invoke-Command -ComputerName $servers -ScriptBlock {
    Sum-FirstMillionPrimes
}

正如所写的那样，在最慢的机器完成之前，不会显示（产生）结果。

为了加快速度，您尝试将其作为一项工作来执行：

$servers = @("MachineA","MachineB","MachineC")
Invoke-Command -ComputerName $servers -ScriptBlock {
    Sum-FirstMillionPrimes
} -AsJob

while ($null -ne (Get-Job)) {
    $doneChildJob = Get-Job | Wait-Job -Any
    $processResult = $doneChildJob | Receive-Job -AutoRemoveJob -Wait
    $processResult
}

这仍然有同样的问题，因为根据文档（示例 8）：

The command uses the AsJob parameter to run the command as a background
job. This command returns a job object that contains two child job
objects, one for each of the jobs run on the two remote computers.

这对我们来说意味着我们正在运行三个子作业，但在所有子作业完成之前父作业不会返回。

你怎么能这样写，子作业的结果将在完成时返回？

我试过的

我们提出了一个似乎有效的解决方案，但这个问题似乎很常见，应该有一种 PowerShell 方法来处理这个问题。

# Create a HashSet of jobs that have already been processed. This is important
# because child jobs cannot be removed via Remove-Job. There doesn't seem to be
# a way to determine if the job has been received
[System.Collections.Generic.HashSet[int]]$processedJobIds = @()
while ($null -ne (Get-Job)) {
    # We only want to attempt to process jobs that have no children that we
    # haven't seen. The -IncludeChildJob parameter allows us to see the nested
    # children jobs from Invoke-Command -AsJob. Because we can't determine if a
    # child job has already been received, we filter based on our above hashset.
    $doneChildJob = Get-Job -IncludeChildJob | Where-Object { $_.ChildJobs.Count -eq 0 -and (-not ($processedJobIds.Contains($_.Id))) } | Wait-Job -Any
    if ($null -eq $doneChildJob) {
        #   The $doneChildJob filter will exclude the parent job created by
        # Invoke-Command -AsJob. However, we still need to eventually remove
        # this job, otherwise we'd hit an infinite loop.
        #   The assumption is that the only way that $doneChildJob will evaluate to
        # $null is if all child jobs have completed. If all child jobs are
        # completed, the remaining job(s) should be safe to remove as they are
        # expected to be parent jobs.
        Get-Job | Remove-Job
    }
    else {
        # We need to process the child jobs
        $processResult = $doneChildJob | Receive-Job -Wait
        $processResult
        $processedJobIds.Add($doneChildJob.Id) | Out-Null
        # By default, Get-Job does not return children jobs (i.e they are
        # parents and can be removed by Remove-Job). Based on this behavior,
        # if $processedJobIds contains any of these jobs, they are safe to
        # remove, and should also be removed from our $processedJobIds list.
        Get-Job | Where-Object { $processedJobIds.Contains($_.Id) } | ForEach-Object {
            $processedJobIds.Remove($_.Id) | Out-Null
            Remove-Job $_
        }
    }
}

鉴于以下代码，我们已经使用这些示例运行了它，并且它似乎可以工作：

Import-Module ThreadJob

$servers = @("MachineA", "MachineB", "MachineC")
$sessions = New-PSSession -ComputerName $servers

Invoke-Command -Session $sessions -ScriptBlock {
    $computerName = [System.Net.Dns]::GetHostName()
    $firstMillionPrimes = Sum-FirstMillionPrimes
    Write-Output "$computerName - $firstMillionPrimes"
} -AsJob | Out-Null

# It should also handle when one of the child jobs fails but not all
Invoke-Command -ComputerName $servers -ScriptBlock {
    $computerName = [System.Net.Dns]::GetHostName()
    if ($computerName -eq "MachineA") {
        Throw "This is a remote invoke FAILURE on $computerName"
    }
    else{
        $computerName = [System.Net.Dns]::GetHostName()
        $firstMillionPrimes = Sum-FirstMillionPrimes
        Write-Output "$computerName - $firstMillionPrimes"
    }
} -AsJob | Out-Null

# In addition to the jobs started on multiple sessions, this also needs
# to be robust enough to handle other jobs running locally.
Start-Job -ScriptBlock { Sum-FirstMillionPrimes } | Out-Null

# It also needs to handle jobs created by Start-ThreadJob
Start-ThreadJob -ScriptBlock { Sum-FirstMillionPrimes } | Out-Null

# It also needs to handle jobs that have a state of Failed
Start-ThreadJob -ScriptBlock { throw "My job State will be Failed" } | Out-Null

# It should handle nested jobs that are successful
Start-Job -ScriptBlock { Start-ThreadJob -ScriptBlock { Sum-FirstMillionPrimes } | Receive-Job -Wait} | Out-Null
Start-Job -ScriptBlock { Start-Job -ScriptBlock { Sum-FirstMillionPrimes } | Receive-Job -Wait} | Out-Null
Start-ThreadJob -ScriptBlock { Start-ThreadJob -ScriptBlock { Sum-FirstMillionPrimes } | Receive-Job -Wait} | Out-Null

# It should handle nested jobs that are failures
Start-Job -ScriptBlock { Start-ThreadJob -ScriptBlock { throw "Handles nested thread jobs that fail" } | Receive-Job -Wait} | Out-Null
Start-Job -ScriptBlock { Start-Job -ScriptBlock { throw "Handles nested jobs that fail" } | Receive-Job -Wait} | Out-Null
Start-ThreadJob -ScriptBlock { Start-ThreadJob -ScriptBlock { throw "Handles nested thread jobs in thread jobs that fail" } | Receive-Job -Wait} | Out-Null

预期输出（模拟），这将在处理完成时返回给终端。在异常的情况下，它几乎是瞬时的，但在长时间的计算中，结果可能会在它们完成时穿插：

This is a remote invoke FAILURE on MachineA
    + CategoryInfo          : OperationStopped: (This is a remote invoke FAILURE on MachineA:String) [], RuntimeException
    + FullyQualifiedErrorId : This is a remote invoke FAILURE on MachineA
    + PSComputerName        : MachineA
My job State will be Failed
    + CategoryInfo          : InvalidResult: (:) [], RuntimeException
    + FullyQualifiedErrorId : JobStateFailed
Handles nested thread jobs that fail
    + CategoryInfo          : InvalidResult: (:) [], RuntimeException
    + FullyQualifiedErrorId : JobStateFailed
Handles nested jobs that fail
    + CategoryInfo          : InvalidResult: (:) [], RuntimeException
    + FullyQualifiedErrorId : JobStateFailed
Handles nested thread jobs in thread jobs that fail
    + CategoryInfo          : InvalidResult: (:) [], RuntimeException
    + FullyQualifiedErrorId : JobStateFailed
Localhost - (FirstMillionPrimes)
MachineC - (FirstMillionPrimes)
Localhost - (FirstMillionPrimes)
Localhost - (FirstMillionPrimes)
MachineC - (FirstMillionPrimes)
Localhost - (FirstMillionPrimes)
MachineB - (FirstMillionPrimes)
Localhost - (FirstMillionPrimes)
MachineB - (FirstMillionPrimes)
MachineA - (FirstMillionPrimes)

我们提出的这个解决方案似乎有效，但它似乎非常笨拙。PowerShell 中是否有更好的方法/模式可以在结果完成时产生结果？

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