vSphere DSC Test-VmwDscConfiguration Error

Introduction

With the recent release of vSphere DSC 2.2 it has introduced the capability to use DSC without using a Windows machine to apply the configuration. I started investigating using this new method for applying DSC configurations against a vSphere environment and hit an issue at the Test phase of my configuration testing. I thought I would document the issue and simple workaround here.

At the time of this blog post I was using:

• vSphere DSC v2.2.0.84
• VMware PS Desired State Configuration module v1.0.0.16
• PowerCLI v12.3.0.17860403
• PowerShell v5.1
• Windows 10
• vCenter Server 7.0 Update 2b

If you want a guide on vSphereDSC see my earlier blog post series vSphere DSC - Part 1.

The DSC Configuration

I created a very simple configuration to create a Datacenter called ‘vGemba-DC’ on my VCSA:

$Credential = Import-CliXml -path C:\Creds\admin.xml

Configuration Datacenter_Config {
    Import-DscResource -ModuleName VMware.vSphereDSC

    Node localhost {
        Datacenter vGemba-Datacenter {
            Server = 'vcsa01.corp.contoso.com'
            Credential = $Credential
            Name = 'vGemba-DC'
            Location = ''
            Ensure = 'Present'
        }
    }
}

You can see it is pretty simple. I am pulling credentials from an encrypted xml file as I described in a previous blog post Saving PowerCLI Credentials. As it’s my lab this is a way of me having to repeatedly enter credentials.

Next I am using the DSC Resource Datacenter to ensure there is a datacenter called vGemba-DC on my vCenter vcsa01.corp.contoso.com. Very straightforward stuff to create and make sure there is a datacenter. I have saved this file under the name new-vmwdc.ps1.

Creating the configuration object

Before this release of vSphereDSC your only choice was to create the mof file on a Windows computer and then apply that mof to the vSphere environment. Now with the module VMware.PSDesiredStateConfiguration installed we can create an object which contains the details of the configuration:

PS C:\Repos\vsphere-dsc> $dscconfig = New-VmwDscConfiguration -Path .\new-vmwdc.ps1

Now we can check the object was created correctly as nothing is returned:

PS C:\repos\vsphere-dsc> $dscconfig

Nodes       InstanceName
-----       ------------
{localhost} Datacenter_Config

Test DSC Compliance - The Error

To check, I start a PowerCLI session to my vCenter and check which datacenter’s are present:

PS C:\repos\vsphere-dsc> Get-Datacenter

Name
----
DC01

So the desired datacenter called vGemba-DC is not there. To check now using DSC we use the cmdlet Test-VmwDscConfiguration. This of this as the equivalent of Test-DscConfiguration in ‘traditional’ DSC:

PS C:\Repos\vsphere-dsc> Test-VmwDscConfiguration -Configuration $dscconfig
Select-Object : Property "InvokeResult" cannot be found.
At C:\Program Files\WindowsPowerShell\Modules\VMware.PSDesiredStateConfiguration\1.0.0.16\Functions\Public\Test-VmwDscC
onfiguration.ps1:76 char:35
+ ...  = ($testResults | Select-Object -ExpandProperty InvokeResult | Where ...
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (System.Collections.Hashtable:PSObject) [Select-Object], PSArgumentExce
   ption
    + FullyQualifiedErrorId : ExpandPropertyNotFound,Microsoft.PowerShell.Commands.SelectObjectCommand

True

There is the error which is the point of this post. When I hit this bug I decided to try with the -Detailed parameter to see if I could get more information:

PS C:\Repos\vsphere-dsc> Test-VmwDscConfiguration -Configuration $dscconfig -Detailed

InDesiredState ResourcesInDesiredState ResourcesNotInDesiredState     NodeName
-------------- ----------------------- --------------------------     --------
         False {}                      {Datacenter vGemba-Datacenter} localhost

With the -Detailed parameter Test-VmwDscConfiguration works. This seems to indicate a bug in the cmdlet/module.

The Error

As I could narrow this down to a particular cmdlet I decided to open a bug on the GitHub site for vSphere DSC but I discovered someone had already done this. Bug #323 describes the issue exactly. Seems to be specific to using this cmdlet without -Detailed running under PowerShell v5.1. According to the fix this is due to:

Fix bug with Test-VmwDscConfiguration cmdlet on PowerShell 5.1 that occurred due to NodeResult being PSObject instead of PSCustomObject. Select-Object -ExpandProperty InvokeResult doesn’t work on PSObject on PowerShell 5.1.

So it looks like in a future release of vSphere DSC this will be fixed.

Wrap Up

This is a PSA to others trying out the new method of invoking DSC configurations. Apart from this bug it’s working well for me and I like it as it removes an additional step of creating the mof files. Go try out vSphere DSC 2.2 but just remember to use -Detailed. I will update this post once the fix is rolled out in a future release.