如何创建在完成时产生结果的工作？

Question

问题

假设您有 4 台机器。

• 机器 A 很慢
• 机器 B 为中速，
• 机器 C 很快。
• Lo​​calHost 速度超快。

在每台远程计算机上，您希望将前 100 万个素数相加。您可以从本地主机执行此操作：

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

正如本文所写，在最慢的机器完成之前，不会显示（生成）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
}

这个还是有同样的问题，因为根据the documentation (example 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。

如何编写这样的代码，使子作业的结果在完成时返回？

我的尝试

我们提出了一个似乎可行的解决方案，但这个问题似乎很常见，应该有一个 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到终端。在异常的情况下，几乎是瞬间完成的，但在长时间的计算中，结果可能会在完成时穿插：

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可行，但看起来确实很重。 PowerShell 中是否有更好的方法/模式可以在完成时产生结果？

Answer 1

听起来像 PSRemotingJob.StateChanged 事件可能对您有用。像这样的：

$global:results = [System.Collections.ArrayList]::new()

# create action scriptblock for eventhandling
$onJobFinish = {
    # only run action if job has terminated
    if ($Event.Sender.State -in @('Completed', 'Failed', 'Stopped', 'Suspended', 'Disconnected')) {
        $localResults = $Event.Sender | Receive-Job

        # immediately send output to screen
        $localResults | Out-Host

        # also add output to collection to work with later
        $global:results.Add($localResults) | Out-Null
    }
}

Invoke-Command -Session $sessions -ScriptBlock {
    $computerName = [System.Net.Dns]::GetHostName()
    $firstMillionPrimes = Sum-FirstMillionPrimes
    Write-Output "$computerName - $firstMillionPrimes"
} -AsJob | 
    Select-Object -ExpandProperty ChildJobs | ForEach-Object {
    # Register our action to run wheneven a child job's state changes
        Register-ObjectEvent -InputObject $_ -EventName 'StateChanged' -Action $onJobFinish
    }

Start-Job -ScriptBlock { Sum-FirstMillionPrimes } | Select-Object -ExpandProperty ChildJobs | ForEach-Object {
    # Register our action to run wheneven a child job's state changes
    Register-ObjectEvent -InputObject $_ -EventName 'StateChanged' -Action $onJobFinish
}

# access all results that have been received thus far
$global:results | Format-Table

更新

您也可以执行类似的操作，只需将所有作业添加到单个集合中，并在它们运行/有数据时执行循环。您可以通过这种方式输出可用的数据，而不必等待作业完成。

$jobs = @()
$jobs += Invoke-Command -ScriptBlock $sb -ComputerName $computers -AsJob
$jobs += Start-Job -ScriptBlock $sb2
$jobs += Start-ThreadJob -ScriptBlock $sb3

$results = [System.Collections.ArrayList]::new()

while ($jobs | Where-Object { 
        $_.State -notin @('Completed', 'Failed', 'Stopped', 'Suspended', 'Disconnected') 
    }) {
    $localData = $jobs | Receive-Job
    $localData | Format-Table
    $results.Add($localData) | Out-Null

    Start-Sleep -Seconds 1
}
# Add one more collection of data for good measure
$localData = $jobs | Receive-Job
$localData | Format-Table
$results.Add($localData) | Out-Null