Terraform Modules in Azure: Step-by-Step Guide with Count, for_each & YAML Examples

 

Introduction

In modern cloud environments, writing reusable and scalable infrastructure is critical. Using Terraform with Microsoft Azure, you can achieve this efficiently through Terraform modules.

This blog provides:
✅ Simple module example
✅ count implementation
✅ for_each implementation
✅ YAML-based configuration
✅ Fully working step-by-step code

---

📦 Step 1: Simple Terraform Module (Basic Example)

📁 Folder Structure

project/
├── main.tf
├── provider.tf
└── modules/
    └── rg/
        ├── main.tf
        ├── variables.tf
        └── outputs.tf

---

🔹 Module Code

modules/rg/main.tf

resource "azurerm_resource_group" "rg" {
  name     = var.rg_name
  location = var.rg_location
}

modules/rg/variables.tf

variable "rg_name" {
  type = string
}

variable "rg_location" {
  type = string
}

modules/rg/outputs.tf

output "rg_name" {
  value = azurerm_resource_group.rg.name
}

---

🔹 Root Module

provider.tf

provider "azurerm" {
  features {}
}

main.tf

module "rg" {
  source = "./modules/rg"

  rg_name     = "demo-rg"
  rg_location = "eastus"
}

---

▶️ Run

terraform init
terraform plan
terraform apply

---

🔁 Step 2: Using count in Module (Multiple Resources)

variable "rg_names" {
  default = ["rg-dev", "rg-test", "rg-prod"]
}

module "rg" {
  source = "./modules/rg"

  count       = length(var.rg_names)
  rg_name     = var.rg_names[count.index]
  rg_location = "eastus"
}

👉 Creates:

• rg-dev
• rg-test
• rg-prod

---

🔄 Step 3: Using for_each (Recommended)

variable "rgs" {
  default = {
    dev  = "rg-dev"
    test = "rg-test"
    prod = "rg-prod"
  }
}

module "rg" {
  source = "./modules/rg"

  for_each = var.rgs

  rg_name     = each.value
  rg_location = "eastus"
}

---

📤 Output

output "rg_names" {
  value = {
    for key, mod in module.rg :
    key => mod.rg_name
  }
}

---

🧾 Step 4: Using YAML Configuration (Advanced)

📁 config.yaml

resource_groups:
  dev: rg-dev
  test: rg-test
  prod: rg-prod

---

🔹 Terraform Code

locals {
  config = yamldecode(file("${path.module}/config.yaml"))
}

module "rg" {
  source = "./modules/rg"

  for_each = local.config.resource_groups

  rg_name     = each.value
  rg_location = "eastus"
}

---

🧠 Key Concepts

Feature	Use
Module	Reusable code
count	Simple iteration
for_each	Map-based iteration
YAML	External config

---

⚖️ Count vs for_each

Feature	count	for_each
Input	List	Map
Stability	❌ Index-based	✅ Key-based
Recommended	⚠️ Limited	✅ Yes

---

🎯 Best Practices

• Use modules for reusable design
• Prefer for_each over count
• Use YAML for external configuration
• Keep modules small and focused
• Avoid hardcoding values

---

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• Terraform
• Microsoft Azure

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---

🚀 Conclusion

Terraform modules are essential for building scalable, reusable, and production-ready infrastructure.

By mastering:

• Basic modules
• count
• for_each
• YAML configs

👉 You become a real-world DevOps engineer

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🔥 Hashtags

#Terraform #Azure #DevOps #InfrastructureAsCode #CloudAutomation #TerraformModules #EduArn