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Non-Linear Workflows

Basics

A documented example of the basic workflow setup can be found on this page.

Description

In many simple workflows, there is a strict sequence of actions taken: Step 1, then Step 2 and finally Step 3. A linear sequence of actions, similar to commands on a single PowerShell pipeline.

Well, nothing says Runspace Workflows must be linear.

Any given worker only looks to its own InQueue for work orders. Using the Write-PSFRunspaceQueue command it is quite possible to provide values to more than just one out queue:

$workflow = New-PSFRunspaceWorkflow -Name 'ExampleWorkflow-MultiPronged'

# Define Workers
$workflow | Add-PSFRunspaceWorker -Name ADUser -InQueue Input -OutQueue Users -Count 5 -ScriptBlock {
    param ($Value)
    Get-ADUser -Identity $Value
}
$workflow | Add-PSFRunspaceWorker -Name Filter -InQueue Users -OutQueue goodUsers -Count 1 -ScriptBlock {
    param ($Value)
    if ($Value.SamAccountName -notmatch '^[a-z]{1}\d{6}[abc]$') {
        Write-PSFRunspaceQueue -Name badUsers -Value $Value
        return
    }
    $Value
}
$workflow | Add-PSFRunspaceWorker -Name BadUser -InQueue badUsers -OutQueue Completed -Count 3 -ScriptBlock {
    param ($Value)
    Send-BadUserReport -User $Value
    $Value
}
$workflow | Add-PSFRunspaceWorker -Name GoodUsers -InQueue goodUsers -OutQueue Completed -Count 3 -ScriptBlock {
    param ($Value)
    Send-GoodUserReport -User $Value
    $Value
}
$workflow | Add-PSFRunspaceWorker -Name PostProcessing -InQueue Completed -OutQueue AllUsers -Count 1 -ScriptBlock {
    param ($Value)
    $Value.SamAccountName
}

# Execute
$workflow | Write-PSFRunspaceQueue -Name Input -BulkValues (Get-Content .\users.txt)
$workflow | Start-PSFRunspaceWorkflow -PassThru | Wait-PSFRunspaceWorkflow -WorkerName PostProcessing -ReferenceQueue Users -PassThru | Stop-PSFRunspaceWorkflow
$results = $workflow | Read-PSFRunspaceQueue -Name AllUsers -All
$workflow | Remove-PSFRunspaceWorkflow

In this workflow we …

1: Retrieve the AD User object for each user provided to input
2: Match the account against a specified pattern and either send it on to the queue for 3a (badUsers) or 3b (goodUsers)
3a: Reports on bad users and sends it on to 4
3b: Reports on good users and sends it on to 4
4: Provides the SamAccountName of all users, irrespective of whether they come from 3a or 3b

In other words, it is perfectly fine for data flows to split between workers and queues, so long as we keep in mind how we are going to track successful conclusion. Wait-PSFRunspaceWorkflow can compare the number of items that went through one worker with the total number another queue held to help make that determination, when closing out queues becomes difficult.

Next Steps

Back to Runspace Workflows