APIM: behaviour of zones in additional_location differs from behaviour of zones in parent resource

[CherylFlowers]

Is there an existing issue for this?

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Terraform Version

1.3.8

AzureRM Provider Version

3.106.1

Affected Resource(s)/Data Source(s)

azurerm_api_management

Terraform Configuration Files

resource "azurerm_api_management" "api_management" {
  name                = "test"
  resource_group_name = "test-rg"
  location            = "canada central"  
  sku_name            = "Premium"
  publisher_name      = "test"
  publisher_email     = "[email protected]"
  zones               = ["1"]

  additional_location {
    location = "southeast asia"
    zones    = ["1", "2"]
  }
}

Debug Output/Panic Output

+ additional_location {
+ capacity             = (known after apply)
+ gateway_disabled     = false
+ gateway_regional_url = (known after apply)
+ location             = "southeastasia"
+ private_ip_addresses = (known after apply)
+ public_ip_addresses  = (known after apply)
+ zones                = [
+ "1",
+ "2",
] # forces replacement
}

Expected Behaviour

When adding a brand new additional_location to an existing APIM instance, the zones argument should not trigger a replacement, regardless of the value.

Actual Behaviour

When adding a brand new additional_location to an existing APIM instance, if the zones field is configured, it triggers a replacement of the APIM instance. If the zones field is omitted, it does not trigger a replacement.

Steps to Reproduce

1. Provision an APIM instance with no additional_location.
2. Add additional_location and omit the zones argument.
3. Run a terraform plan and note that the plan does not force a replacement of the APIM instance.
4. Add the zones field to additional_location.
5. Run a terraform plan and note that the plan now forces a replacement of the APIM instance.

Important Factoids

No response

References

It appears this pull request may be related to this unexpected behaviour. It appears that the functionality of the zones argument was updated for the APIM instance itself, but the same changes were not made to the additional_location argument.

[sinbai]

Hi @CherylFlowers thanks for opening this issue. Per the Terraform documentation below, changing zone of additional_locationforces a new resource to be created. I assume that the symptom is expected. Is it possible to explain why this case should not trigger a replacement?

[klakshmikantha]

Hi @sinbai - Thank you for the response. Changing or setting the zones under 'additional_location' should re-create the data plane resource deployed in that region but not the entire control plane of APIM which is what is happening now. The zones at root level for control plane should drive recreation of the control plane but not the zones under each additional location block.
This is especially important as we add additional data planes in the future spanning geographies but can't afford to re-create control plane risking the configurations/APIs/products etc. already setup and also not impact other region data planes.
The zone setting under the additional_location block should only re-create the data plane in that location.

[sinbai]

Hi @klakshmikantha thanks for your reply. PR has been submitted to remove the replacement when the zone in additional_location changes. Could you please track it for more updates?

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