DnsRecordBase: Test returns that desired state and current state is equal even if the record does not exist

[Johan Ljunggren]

I wasn't expecting to see that current state and desired state to be equal in the integration test. I would have expected it to just report that the record is missing and not comparing the other properties. 🤔

VERBOSE: [fv-az59-142]: LCM:  [ Start  Test     ]  [[DnsRecordSrv]Integration_Test]
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] Calling GetResourceRecord() from the DnsRecordSrv class to get the object's current state.
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] Getting DNS record '_dummy._tcp' with target of 'dummy.contoso.com' (SRV) in zone 'srv.test' from 'localhost'.
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] A matching DNS resource record not found.
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.String') for property 'SymbolicName' does match. Current state is 'dummy' and desired state is 'dummy'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.UInt16') for property 'Weight' does match. Current state is '20' and desired state is '20'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.String') for property 'DnsServer' does match. Current state is 'localhost' and desired state is 'localhost'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.String') for property 'ZoneName' does match. Current state is 'srv.test' and desired state is 'srv.test'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.UInt16') for property 'Port' does match. Current state is '33179' and desired state is '33179'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.String') for property 'Target' does match. Current state is 'dummy.contoso.com' and desired state is 'dummy.contoso.com'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] NOTMATCH: Value (type 'Ensure') for property 'Ensure' does not match. Current state is 'Absent' and desired state is 'Present'. (DRC0021)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.UInt16') for property 'Priority' does match. Current state is '10' and desired state is '10'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] MATCH: Value (type 'System.String') for property 'Protocol' does match. Current state is 'TCP' and desired state is 'TCP'. (DRC0020)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] Compare-DscParameterState result : Property 'Ensure' is in desired state 'False' . (DRC0026)
VERBOSE: [fv-az59-142]:                            [[DnsRecordSrv]Integration_Test] DNS record is NOT in the desired state.
VERBOSE: [fv-az59-142]: LCM:  [ End    Test     ]  [[DnsRecordSrv]Integration_Test]  in 0.5560 seconds.

Originally posted by @johlju in #201 (comment)

[James Sudbury]

@johlju , below is my analysis of the issue. I would be interested to hear your take.

Process flow:

• The Test() method calls Get() to compare the current state with the desired state.
• The Get() method determines the resource was not found, sets the expected values in the object, and flags the object returned with an Ensure value of 'Absent'.
• The Test() method then uses the Compare-DscParameterState function to determine whether the current state and desired state match. This function evaluates against the entire object.

Possible courses of action:

• The process flow is working as intended. Leave it as-is.
• The process flow is working as intended. Add another verbose message explaining that the current state is being compared to the desired state.
• Short-circuit the call to Compare-DscParameterState with the full set of parameters by explicitly comparing current and expected Ensure values first in DnsRecordBase (Compare-DscParameterState can still be used here. It just requires a preemptive call passing only 'Ensure' to the Properties parameter).
• Modify the Compare-DscParameterState function to short-circuit itself based on the Ensure value comparisons.

Thoughts:

I believe that the process is working as intended and that additional comments would just be stating that the test is occurring - which users of DSC should already understand. I am happy to leave it as-is.

If, however, the desire is to cut down the processing that occurs in making this determination, I believe a change would be more appropriate in Compare-DscParameterState than in DnsRecordBase.

[Johan Ljunggren]

I think we Test() should just call Compare-DscParameterState if Ensure for desired state and actual state is Present.
So the code

https://github.com/dsccommunity/xDnsServer/blob/2303e2e46e87ffc8e1678bc58b257ba812a862a3/source/Classes/001.DnsRecordBase.ps1#L209-L226

Would become.

if ($this.Ensure -eq 'Present')
{
    if ($currentState.Ensure -eq 'Present')
    {
        # Remove properties that have $null as the value
        @($desiredState.Keys) | ForEach-Object -Process {
            if ($null -eq $desiredState[$_])
            {
                $desiredState.Remove($_)
            }
        }

        # Returns all enforced properties not in desires state, or $null if all enforced properties are in desired state
        $propertiesNotInDesiredState = Compare-DscParameterState -CurrentValues $currentState -DesiredValues $desiredState -Properties $desiredState.Keys -ExcludeProperties @('Ensure')

        if ($propertiesNotInDesiredState)
        {
            $isInDesiredState = $false
        }
    }
    else 
    {
        $isInDesiredState = $false
    }
}

It adds an evaluate of the Ensure property. If the record exist the Ensure property is excluded from Compare-DscParameterState using ExcludeProperties when comparing the state of the properties since it has already been evaluated

Would that work?

[James Sudbury]

That looks clean and makes sense. I'm good with it. Would you like to work the change, or would you prefer I take it for action?

Note: For the sake of anyone reading in the future, we have agreed on course of action # 3 above.

[Johan Ljunggren]

I can fix it, it is a small change, then you can focus on the large changes like adding new resources 😉