PowerShell 7. ForEach-Object -Parallel Does Not Autheticate Against Azure PowerShell - azure-powershell

Question

We wrote a script that supposed to execute Azure PowerShell commands in parallel. The problem is when we increase -ThrottleLimit higher than one, some of the commands are not being performed properly. The script is:
# Writing IPs for whitelisting into file.
Add-Content -Path IPs.txt -Value ((Get-AzWebApp -ResourceGroupName "ResourceGroup1" -Name "WebApp1").OutboundIpAddresses).Split(",")
Add-Content -Path IPs.txt -Value ((Get-AzWebApp -ResourceGroupName "ResourceGroup1" -Name "WebApp1").PossibleOutboundIpAddresses).Split(",")
# Writing new file with inique IPs.
Get-Content IPs.txt | Sort-Object -Unique | Set-Content UniqueIPs.txt
# Referencing the file.
$IPsForWhitelisting = Get-Content UniqueIPs.txt
# Assigning priotiry number to each IP
$Count = 100
$List = foreach ($IP in $IPsForWhitelisting) {
$IP|Select #{l='IP';e={$_}},#{l='Count';e={$Count}}
$Count++
}
# Whitelisting all the IPs from the list.
$List | ForEach-Object -Parallel {
$IP = $_.IP
$Priority = $_.Count
$azureApplicationId ="***"
$azureTenantId= "***"
$azureApplicationSecret = "***"
$azureSecurePassword = ConvertTo-SecureString $azureApplicationSecret -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential($azureApplicationId , $azureSecurePassword)
Connect-AzAccount -Credential $credential -TenantId $azureTenantId -ServicePrincipal | Out-null
echo "IP-$Priority"
echo "$IP/24"
echo $Priority
Add-AzWebAppAccessRestrictionRule -ResourceGroupName "ResourceGroup1" -WebAppName "WebApp1" -Name "IP-$Priority" -Priority $Priority -Action Allow -IpAddress "$IP/24"
} -ThrottleLimit 1
If ThrottleLimit is set to 1 - 8 rules are being created, if ThrottleLimit is set to 2 - 7 rules are being created, 3 - 4 rules, 10 - 1 rule, hence some rules are being skipped.
What is the reason for such behavior?

Answer 1

In short - the -Parallel parameter does not (yet perhaps) magically import all dependent variables that fall in the scope of the For-EachObject block. In reality PWSH spans separate processes and only the array that is looped over will be implicitly passed, all other variables need explicit designations.
One should use the $using: directive (prefix) to denote which variables are to be imported (made visible) in the parallel code block.
Example:
$avar = [Int]10
$bvar = [Int]20
$list = #('here', 'it', 'eees')
$list | ForEach-Object -Parallel {
Write-Output "(a, b) is here ($($using:avar), $($using:bvar))"
Write-Output "(a, b) missing ($($avar), $($bvar))"
Write-Output "Current element is $_"
}```
*thus - the described behavior is likely due to the fact that config. variables are not imported (at all) and thus the operations silently fail.*