azurerm_monitor_diagnostic_setting - fix log_analytics_destination_type

[teowa]

resolves #20140

The issue is caused by service API behavior change and related to #20048:

• Before: some resources had log_analytics_destination_type property default to AzureDiagnostics. So PR azurerm_monitor_diagnostic_setting - fix update issue  #20048 was introduced to set TF schema property default to AzureDiagnostics.
• Now: some resources (e.g. azurerm_key_vault) returns empty for log_analytics_destination_type property even if you set it as AzureDiagnostics or Dedicated in request. But some other resources (e.g. azurerm_data_factory) still default to AzureDiagnostics. Details is in Microsoft.Insights/diagnosticSettings@2021-05-01-preview - logAnalyticsDestinationType break PUT-GET consistency Azure/azure-rest-api-specs#22400.

The above API behavior change happened after PR #20048 (set log_analytics_destination_type default to AzureDiagnostics) was merged. Days ago the API also returns AzureDiagnostics for resource like Key Vault, this can be proved by daily test record, it works well before Jan 26, and PR #20048 was merged before Jan 19.

From this doc:

Most Azure resources write data to the workspace in either Azure diagnostics or resource-specific mode without giving you a choice. For more information, see Common and service-specific schemas for Azure resource logs.

All Azure services eventually use the resource-specific mode. As part of this transition, some resources allow you to select a mode in the diagnostic setting. Specify resource-specific mode for any new diagnostic settings because this mode makes the data easier to manage. It also might help you avoid complex migrations later.

[Klaas-]

@teowa the doc you linked, https://github.com/MicrosoftDocs/azure-docs/blob/e294e228cf8249e82172695143e0a21084636b67/articles/azure-monitor/essentials/resource-logs.md#select-the-collection-mode , it says that we should use Dedicated because AzureDiagnostics will be removed in future, right? So we should maybe put a deprecaion on that and change default in 4.0 or something like that?

[teowa]

As I tested, for some target resources (e.g., KeyVault) this property is not settable, and for other resources (e.g., DataFactory) it still works well, see details in Azure/azure-rest-api-specs#22400. I am still contacting with service team about the details of the affected resource types. Temporarily close this and once a solution is determined I am going to reopen this PR.

[teowa]

The two cases of log_analytics_destination_type property:

1. for resources (Keyvault), the property is no longer applicable, either set AzureDiagnostics or Dedicated, returns null
2. for others (DataFactory), defaults to AzureDiagnostics but can also be changed to Dedicated.

We are asking service team to change case1 to return an error. And I think it's better to change this property to Computed for now, from the doc, case1 is more common and set this as computed can remove the diff noise for users who dont set this property.

[katbyte]

LGTM 📓

[github-actions]

This functionality has been released in v3.45.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.