Update of Azure Web App using runtime NodeJS can unset the NodeJS version leading to crash

[Apokalypt]

Is there an existing issue for this?

• I have searched the existing issues

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Terraform Version

1.7.5

AzureRM Provider Version

3.86.0 (verified on 3.87.1)

Affected Resource(s)/Data Source(s)

azurerm_windows_web_app

Terraform Configuration Files

terraform {
  required_version = ">= 0.13"
  required_providers {
    azurerm = {
      source  = "hashicorp/azurerm"
      version = "~> 2"
    }
    random = {
      source  = "hashicorp/random"
      version = "~> 3"
    }
  }
}

provider "azurerm" {
  features {}
}

provider "random" {}

resource "random_string" "unique" {
  length  = 4
  lower   = true
  number  = true
  upper   = false
  special = false
}

resource "azurerm_resource_group" "windows" {
  name     = "rg-windows-${random_string.unique.result}"
  location = "centralus"
}

resource "azurerm_app_service_plan" "windows" {
  name                = "plan-windows-${random_string.unique.result}"
  location            = azurerm_resource_group.windows.location
  resource_group_name = azurerm_resource_group.windows.name
  kind                = "Windows"
  reserved            = false # Must be false (the default value) for Windows plans

  sku {
    tier     = "Free"
    size     = "F1"
    capacity = 0
  }
}

resource "azurerm_app_service" "windows" {
  name                = "app-windows-${random_string.unique.result}"
  location            = azurerm_resource_group.windows.location
  resource_group_name = azurerm_resource_group.windows.name
  app_service_plan_id = azurerm_app_service_plan.windows.id

  site_config {
    use_32_bit_worker = true

    application_stack {
      current_stack = "node"
      node_version  = "~18"
    }
  }

  app_settings = {
    "RANDOM_KEY": "random-value"
  }
}

Debug Output/Panic Output

N/A
(I'm not the manager of the terraform file and can't get these informations)

Expected Behaviour

When we need to update the IP restriction, only the IP restriction should be updated and not the App Settings. At the same time, if we need to update the App Settings the node version should not be lost in the process

Actual Behaviour

If the environment variable for NodeJS version is set and we start to update our ip restriction of the windows web app, it's lost in the update without notification leading to Azure using the NodeJS version 0.16.1 (all of our applications instantly crash).
However, if the environment variable for NodeJS version isn't set, Terraform correctly add it

--> Right now, we need to make 2 deployment if we have to change something in App Settings or Site Configuration leading to unacceptable downtime

Steps to Reproduce

1. terraform plan
2. terraform apply

(I'm not the manager of the terraform file and can't get all the commands in details, so you have only the idea indicated)

Important Factoids

N/A

References

Seems related/similar to #16681

[Apokalypt]

I took some time to identify the problem in order to provide a fix. Here is what I understood

Problem Analysis

The main problem comes from the deletion of the NodeJS version environment variable (WEBSITE_NODE_DEFAULT_VERSION) while reading the data (code). From my understanding, this is done to avoid detection of changes in AppSettings during an update since this environment variable should not be set manually and should be automatically handled using application_stack.

And the real problem happen when we are updating the AppSettings information (code). In fact, if we are making a change in AppSettings, "health_check_eviction_time_in_min" or any site configuration (e.g. ip restriction) we enter in this condition and upload AppSetings without setting the appropriate environment variable for the node version
FYI, the NodeJS version environment variable is only set if a change is detected in node_version. For this reason, the problem is solved using a second deployment...

[github-actions]

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