Pipelines cannot be run concurrently

Customers are running into System.Management.Automation.PSInvalidOperationException: The pipeline was not run because a pipeline is already running. Pipelines cannot be run concurrently error when calling Add-AzVhd method from Az.Compute module. Looking at the stack trace, it’s coming from the following method in Automation SDK: System.Management.Automation.Runspaces.PipelineBase.DoConcurrentCheck(Boolean syncCall, Object syncObject, Boolean isInLock)

However, we are not able to reproduce it every time. We are only able to reproduce it successfully around 20% of the time. We are not using any piping in our PS script. Could you guys help us out in determining what the problem might be?

Steps to reproduce

No reliable reproduce method. Personally, I am unable to reproduce it, however another engineer is able to and he has around 20% repro rate. 

# Cosine IOT Services Azure Internal Consumption
$subscriptionId='f9cb372a-8903-4370-9ce0-3042e3bb2cc8'

$rgSeed = "akstest" # TODO customize
$vmSeed = "0430c101a"
$vhdFolder = "C:\Users\jiria\Downloads"
$vhdFileName = "aks-vhd-2.0.20200815.0745.vhd"
$storageAccountName = "storage" + $rgSeed

$location = "westus2"

# $vmSize = "Standard_A2"
$vmSize = "Standard_NC6"

.\vm-create.ps1 $subscriptionId $rgSeed $vmSeed $vhdFolder $vhdFileName $storageAccountName $location $vmSize

Expected behavior

No error

Actual behavior

error: Exception - System.Management.Automation.PSInvalidOperationException: The pipeline was not run because a pipeline is already running. Pipelines cannot be run concurrently. 

Environment data

[rjmholt]

We are not using any piping in our PS script

A pipeline here is what runs the commands. The error message means you’re trying to run multiple commands at the same time on the same thread (i.e. in the same runspace).

In the snippet and error message you’ve shown, there isn’t enough information to establish what’s going on. In particular we don’t know what cmdlets are being used, where the error occurs or any other details about the error. We need:

• The contents of vm-create.ps1 and any other scripts being called – we need to know the whole program you’re running
• The full stack trace of the error, which you can get with Get-Error or $error[0] | fl * -force after you reproduce

[vexx32]

I think they mentioned the cmdlet they ran; Add-AzVhd – I suspect the cmdlet is doing something… unwise… internally if that’s all they ran.