Begin and End

Back to Runspace Workflows

Basics

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

Description

As seen in the basic example, runspace workflows allow defining steps (Workers), where a scriptblock is executed once per input item. That is all great and similar to the process block of the PowerShell pipeline.

But if we have a process, do we also have a begin and end?

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

$begin = {
    $global:sqlInstance = Connect-DbaInstance -SqlInstance sql01.contoso.com\userdb
}
$process = {
    $_ | Write-DbaDataTable -SqlInstance $global:sqlInstance -Database userDB -Table Users
}
$end = {
    Disconnect-DbaInstance $global:sqlInstance
}

$workflow | Add-PSFRunspaceWorker -Name Users -InQueue UserList -OutQueue Users -Count 5 -ScriptBlock {
    Get-ADUser -Identity $_
} -CloseOutQueue
$workflow | Add-PSFRunspaceWorker -Name WriteToDB -InQueue Users -OutQueue Done -Count 1 -Begin $begin -ScriptBlock $process -End $end -CloseOutQueue

# Add values and execute
$workflow | Write-PSFRunspaceQueue -Name UserList -BulkValues $users -Close
$workflow | Start-PSFRunspaceWorkflow -PassThru | Wait-PSFRunspaceWorkflow -WorkerName WriteToDB -Closed -PassThru | Remove-PSFRunspaceWorkflow

We do.

That said, this example also includes one thing not yet covered in the basic example: Closing queues. More on that in another, dedicated example scenario.

Note: Another difference to the basic example is, that the final step will produce no output. While we have to specify an OutQueue, it will never receive items. This also means we never have to read from the queue and can skip over Stop-* and move straight to Remove-PSFRunspaceWorkflow.

Next Steps

• Automatically close queues and workers when done
• Providing variables, functions or modules to the worker code
• How do I avoid spamming a service with too many requests?

Back to Runspace Workflows