azurerm_postgresql_flexible_server: more support for in-place major version upgrade

[wuxu92]

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Description

Per API's behavior of create_mode only works when creating the instance, and upgrade the version of the server should not cause a force-recreate of the resource. I have tested locally, whether create_mode set or not, the version can be upgrade successfully. So this PR changes the force-new logic to only when downgrading the version.

This PR also move some related validation logic from Create to CustomizeDiff, so all the errors can be exposed in plan stage.

The new version update psudo logic:

// if version downgrade
if new_version < old_version:
  set force new and continue

// if version upgrade
if create_mode != "Update" and allow_major_version_upgrade_enabled is not True:
  raise an error of forbidding version update
else:
  in-place update

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Changes to existing Resource / Data Source

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Testing

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--- PASS: TestAccPostgresqlFlexibleServer_upgradeVersion (2564.89s)
--- PASS: TestAccPostgresqlFlexibleServer_updateVersion (1623.36s)
PASS
ok      github.com/hashicorp/terraform-provider-azurerm/internal/services/postgres1623.389s

Change Log

Below please provide what should go into the changelog (if anything) conforming to the Changelog Format documented here.

• azurerm_postgresql_flexible_server - support in-place major version upgrade [changing the azurerm_postgresql_flexible_server version from 11 to any other version forces a recreate #25184]

This is a (please select all that apply):

• Bug Fix
• New Feature (ie adding a service, resource, or data source)
• Enhancement
• Breaking Change

Related Issue(s)

Fixes #25184

Note

If this PR changes meaningfully during the course of review please update the title and description as required.

[nachoalonsoportillo]

Here's my proposal to improve this experience...

Say the user has deployed a server using this block:

resource "azurerm_postgresql_flexible_server" "example" {
  name                          = "example-psqlflexibleserver"
  resource_group_name           = azurerm_resource_group.example.name
  location                      = azurerm_resource_group.example.location
  version                       = "13"
  public_network_access_enabled = true
  administrator_login           = "myadmin"
  administrator_password        = "mypassword"
  storage_mb                    = 32768
  sku_name                      = "B_Standard_B1ms"
  zone                          = 1
  create_mode                   = "Default"
  

My proposal is that we implement some additional allow_major_version_upgrade boolean property, which must be present and set to true for the MVU to be initiated. Although the backend doesn't expect or support any equivalent property, I think it would be good to have so that users don't shoot on their own food and accidentally initiate an irreversible major version upgrade operation:

resource "azurerm_postgresql_flexible_server" "example" {
  name                          = "example-psqlflexibleserver"
  resource_group_name           = azurerm_resource_group.example.name
  location                      = azurerm_resource_group.example.location
  version                       = "15" <<<<<<<<< Bumped up the version
  public_network_access_enabled = true
  administrator_login           = "myadmin"
  administrator_password        = "mypassword"
  storage_mb                    = 32768
  sku_name                      = "B_Standard_B1ms"
  zone                          = 1
  create_mode                   = "Default"
  allow_major_version_upgrade   = true  <<<<<<<<< If value set to version property is higher than current major version on instance, and this property isn't present and set to true, the provider would raise an error requiring its presence.
}

[wuxu92]

@nachoalonsoportillo Thank you for the proposal; it is valuable to some users. However, adding such a property may disrupt existing configurations where create_mode = true, and users can currently upgrade versions without errors. Adding a field like major_version_update_enabled would necessitate manual updates to their configurations. Therefore, I would prefer updating the resource's documentation to include a warning that a version upgrade will result in several minutes of out-of-service time, rather than adding a guardian property to the resource. What do you think?

I also tested to update the create_mode to an existing server and it works, although the GET api doesn't return the create_mode at all. and no matter what the create_mode I updated, the version can be updated in place. So I removed the whole create_mode check here.

[adlerd1]

Hi, when will the fix be merged? We need it to have a proper in-place upgrade using Terraform.

[mbfrahry]

Hey @wuxu92 this looks like we're on the right track but I think we should remove allow_major_version_upgrade_enabled

[mbfrahry]

I agree with your initial assessment to not have a variable for this. Let's remove it

[mbfrahry]

Suggested change

	-> **Note:** Upgrading version wouldn't force a new resource to be created whilst it can still cause the server out of service for a while. Downgrading the version will force a new resource to be created.
	-> **Note:** Downgrading `version` isn't supported and will force a new PostgreSQL Flexible Server to be created.

[wuxu92]

These have been updated. would you please take another look?

[adlerd1]

Hi, when will the fix be merged? We need it to have a proper in-place upgrade using Terraform.

[katbyte]

LGTM 🛋️

[mbfrahry]

LGTM!

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