Crafting Reliable Terraform Configuration via Custom Conditions, Checks, and Variable Validation

In this article, we explore Terraform’s pre/post conditions, check blocks, and variable validation, equipping developers with practical examples for crafting reliable and efficient configurations.

Lifecycle Preconditions and Postconditions

Introduced in Terraform 1.2.0, the lifecycle precondition and postcondition blocks can be attached to resource, data source, or output blocks. During the planning and applying phases, Terraform evaluates these conditions. If any condition fails, Terraform interrupts the plan or apply process.

• Preconditions: Evaluated before provisioning the enclosing block.
• Postconditions: Evaluated after provisioning.

provider "azurerm" {
  features {}
}
resource "azurerm_resource_group" "training" {
  name     = "rg-training-neu-01"
  location = "northeurope"
}
resource "azurerm_app_service_plan" "training" {  
  name                = "asp-training-neu-01" 
  location            = azurerm_resource_group.training.location
  resource_group_name = azurerm_resource_group.training.name 
  sku {  
    tier = "Standard"  
    size = "S1"  
  }   
}  
resource "azurerm_app_service" "training" {  
  name                = "as-training-neu-01"…