Unexpected behavior applying instance protection to scale sets

[autumnrequiem]

Describe the bug

When applying instance protection to a scale set instance via the Azure portal, the behavior is as expected.

Upon reviewing the instance changes, it is noted that only the etag and protectionPolicy were modified.

However, when executing the recommended Azure CLI command:

az vmss update --resource-group --name --instance-id --protect-from-scale-in true

Additional changes are observed in the instance view.

Further investigation revealed that, besides the modifications to the etag and protectionPolicy, several other elements were altered:

The latestModelApplied status changed from true to false.
The modelDefinitionApplied switched from “VirtualMachineScaleSet” to “VirtualMachine”.
The healthProbe was removed from the networkProfileConfiguration.

Same behavior was noticed making call from C# code using latest version of sdk.

To resolve this issue and update the instance to the latest model, I executed another CLI command:

az vmss update-instances --resource-group --name --instance-id

or equivalent call from C# code using sdk.

Related command

az vmss update --resource-group --name --instance-id --protect-from-scale-in true

Errors

Besides the modifications to the etag and protectionPolicy, several other elements were altered:

The latestModelApplied status changed from true to false.
The modelDefinitionApplied switched from “VirtualMachineScaleSet” to “VirtualMachine”.
The healthProbe was removed from the networkProfileConfiguration.

Issue script & Debug output

reproduced_withDebug (2).txt

Expected behavior

Modification of etag and protectionPolicy only

Environment Summary

az --version

azure-cli                         2.65.0 *

core                              2.65.0 *

telemetry                          1.1.0

Dependencies:

msal                              1.31.0

azure-mgmt-resource               23.1.1

Additional context

Customer is setting protection status from c# code using Azure.ResourceManager package

[azure-client-tools-bot-prd]

Hi @autumnrequiem,

2.65.0 is not the latest Azure CLI(2.68.0).

If you haven't already attempted to do so, please upgrade to the latest Azure CLI version by following https://learn.microsoft.com/en-us/cli/azure/update-azure-cli.

[yonzhan]

Thank you for opening this issue, we will look into it.