For azure terraform I am unclear about the output command? - azure

Question

Do not understand when the Output command is used in azure terraform? Where is the output going? Why do we need this output for? We have multiple tf files in aws which I am converting to azure. What type of information is outputted?
Without this output information what would happen?
Please provide examples.
Thank you

Answer 1

A lot of questions, I'm not sure I can cover all this but I can deo give an example.
A good practice would be to build terraform modules, then use the output from these modules to pass along arguments to other modules consuming the same type of input.
The following is a "base module" that creates a resource group, a Vnet, couple of subnets (external and internal for example), NSG and binds the rules to the subnets
resource "azurerm_resource_group" "main_rg" {
name = var.resource_group_name
location = var.location
tags = {
group = var.resource_group_name
Customer = var.tag_reference
stack = "resource group"
}
}
resource "azurerm_virtual_network" "main_vnet" {
name = "${azurerm_resource_group.main_rg.name}-primary-vnet"
address_space = ["${var.vnet_cidr}"]
location = azurerm_resource_group.main_rg.location
resource_group_name = azurerm_resource_group.main_rg.name
tags = {
group = var.resource_group_name
Customer = var.tag_reference
stack = "virtual network"
}
}
resource "azurerm_subnet" "backend_subnet" {
name = "${azurerm_resource_group.main_rg.name}-backend-subnet"
resource_group_name = azurerm_resource_group.main_rg.name
virtual_network_name = azurerm_virtual_network.main_vnet.name
address_prefix = var.backend_subnet_cidr
service_endpoints = ["Microsoft.Sql", "Microsoft.Storage"]
}
resource "azurerm_subnet" "frontend_subnet" {
name = "${azurerm_resource_group.main_rg.name}-frontend-subnet"
resource_group_name = azurerm_resource_group.main_rg.name
virtual_network_name = azurerm_virtual_network.main_vnet.name
address_prefix = var.frontend_subnet_cidr
service_endpoints = ["Microsoft.Sql"]
}
resource "azurerm_network_security_group" "default_nsg" {
name = "${azurerm_resource_group.main_rg.name}-nsg"
location = azurerm_resource_group.main_rg.location
resource_group_name = azurerm_resource_group.main_rg.name
security_rule {
name = "appgwV1Exception"
priority = 100
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "65503-65534"
source_address_prefix = "Internet"
destination_address_prefix = "*"
description = "This is needed to allow helth check of backend server to pass according to official documentation"
}
security_rule {
name = "appgwV2Exception"
priority = 200
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "65200-65535"
source_address_prefix = "Internet"
destination_address_prefix = "*"
description = "This is needed to allow helth check of backend server to pass according to official documentation"
}
security_rule {
name = "Office"
priority = 500
direction = "Inbound"
access = "Allow"
protocol = "*"
source_port_range = "*"
destination_port_range = "443"
source_address_prefix = "1.2.3.4/32"
destination_address_prefix = "*"
description = "Allow 443 access from the office"
}
tags = {
group = var.resource_group_name
Customer = var.tag_reference
stack = "NSG"
}
}
resource "azurerm_subnet_network_security_group_association" "nsg_to_backend" {
network_security_group_id = azurerm_network_security_group.default_nsg.id
subnet_id = azurerm_subnet.backend_subnet.id
}
resource "azurerm_subnet_network_security_group_association" "nsg_to_frontend" {
network_security_group_id = azurerm_network_security_group.default_nsg.id
subnet_id = azurerm_subnet.frontend_subnet.id
}
output "resource_group_name" {
value = azurerm_resource_group.main_rg.name
}
output "vnet_name" {
value = azurerm_virtual_network.main_vnet.name
}
output "vnet_id" {
value = azurerm_virtual_network.main_vnet.id
}
output "backend_subnet_id" {
value = azurerm_subnet.backend_subnet.id
}
output "frontend_subnet_id" {
value = azurerm_subnet.frontend_subnet.id
}
output "nsg_id" {
value = azurerm_network_security_group.default_nsg.id
}
Again the terraform best practice is to use an output file but I'll spare you that for now, see the outputs at the bottom of the file, now I have another module for creating a VM, so my main.tf if you will or the complete file might look a bit something like this:
provider "azurerm" {
version = "~> 1.21"
}
terraform {
backend "azurerm" {}
}
module "base_infra" {
source = "../../base_infra"
location = var.location
resource_group_name = var.resource_group_name
vnet_cidr = var.vnet_cidr
backend_subnet_cidr = var.backend_subnet_cidr
frontend_subnet_cidr = var.frontend_subnet_cidr
tag_reference = var.tag_reference
}
module "webapp_vm" {
source = "../../webapp"
resource_group_name = module.base_infra.resource_group_name
location = var.location
vnet_cidr = module.base_infra.main_vnet_id
subnet_id = module.base_infra.backend_subnet_id
tag_reference = var.tag_reference
datadisk_size_gb = "200"
instance_count = "1"
instance_name_prefix = "${module.base_infra.resource_group_name}-webapp"
vm_size = var.vm_size
vm_username = var.vm_username
vm_password = module.webapp_vm_password.password_result
}
I did cut some corners in my answer, hope I gave you enough