Terraform Dynamic Blocks

Step-01: Introduction

• Understand about Dynamic Block
• Some resource types include repeatable nested blocks in their arguments, which do not accept expressions
• You can dynamically construct repeatable nested blocks like setting using a special dynamic block type, which is supported inside resource, data, provider, and provisioner blocks
• Understand and use sum function using Terraform Console
• Azure Network Resource Group

Step-02: Review c1-versions.tf

• Standard file without any changes

# Terraform Block
terraform {
  required_version = ">= 1.0.0"
  required_providers {
    azurerm = {
      source = "hashicorp/azurerm"
      version = ">= 2.0" 
    }
  }
}
# Provider Block
provider "azurerm" {
 features {}          
}

Step-03: Review c2-resource-group.tf

# Resource-1: Azure Resource Group
resource "azurerm_resource_group" "myrg" {
  name = "myrg-1"
  location = "East US"
}

Step-04: Review c3-network-security-group-regular.tf

# Resource-2: Create Network Security Group
resource "azurerm_network_security_group" "mynsg" {
  name                = "mynsg-1"
  location            = azurerm_resource_group.myrg.location
  resource_group_name = azurerm_resource_group.myrg.name

  security_rule {
    name                       = "inbound-rule-1"
    description                = "Inbound SSH Rule"
    priority                   = 100
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "22"
    destination_port_range     = "22"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
  security_rule {
    name                       = "inbound-rule-2"
    description                = "Inbound HTTP Rule"    
    priority                   = 101
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "80"
    destination_port_range     = "80"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
  security_rule {
    name                       = "inbound-rule-3"
    description                = "Inbound Tomcat Rule"    
    priority                   = 102
    direction                  = "Inbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "8080"
    destination_port_range     = "8080"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }
  security_rule {
    name                       = "outbound-rule-1"
    priority                   = 100
    direction                  = "Outbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "*"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  } 
  tags = {
    environment = "Dev"
  }
}

Step-05: Terraform Sum Function using Terraform Console

# Terraform Console
sum([100,1])
sum([100,2])

Step-06: c4-network-security-group-dynamic-block.tf

• security_rule.key = 0 and security_rule.value = 22
• security_rule.key = 1 and security_rule.value = 80
• security_rule.key = 2 and security_rule.value = 8080 ....

# Define Ports as a list in locals block
locals {
  ports = [22, 80, 8080, 8081, 7080, 7081] 
}
# Resource-2: Create Network Security Group
# Define Ports as a list in locals block
locals {
  ports = [22, 80, 8080, 8081, 7080, 7081]
}

# Resource-2: Create Network Security Group
resource "azurerm_network_security_group" "mynsg2" {
  name                = "mynsg-2"
  location            = azurerm_resource_group.myrg.location
  resource_group_name = azurerm_resource_group.myrg.name

  dynamic "security_rule" {
    for_each = local.ports 
    content {
      name                       = "inbound-rule-${security_rule.key}"
      #name                       = "inbound-rule-${security_rule.value}"
      description                = "Inbound Rule ${security_rule.key}"    
      priority                   = sum([100, security_rule.key])
      direction                  = "Inbound"
      access                     = "Allow"
      protocol                   = "Tcp"
      source_port_range          = security_rule.value
      destination_port_range     = security_rule.value
      source_address_prefix      = "*"
      destination_address_prefix = "*"      
    }
  }

  security_rule {
    name                       = "Outbound-rule-1"
    description                = "Outbound Rule"    
    priority                   = 102
    direction                  = "Outbound"
    access                     = "Allow"
    protocol                   = "Tcp"
    source_port_range          = "*"
    destination_port_range     = "*"
    source_address_prefix      = "*"
    destination_address_prefix = "*"
  }    
  tags = {
    environment = "Dev"
  }  
}

Step-07: Execute Terraform Commands

# Terraform Initialize
terraform init

# Terraform Validate
terraform validate

# Terraform Plan
terraform plan

# Terraform Apply
terraform apply -auto-approve

Step-08: Clean-Up

# Terraform Destroy
terraform destroy -auto-approve

# Delete Files
rm -rf .terraform*
rm -rf terraform.tfstate*