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Build a Local Terraform Module

Step-01: Introduction

  • We will build a Terraform local module to host a static website on Azure Storage Account.
  • We will understand how to call a Local Re-usable module in to a Root Module.
  • We will understand how the local module variables becomes the arguments inside a module block when it is called in Root Module c3-static-webiste.tf
  • We will understand how we define the output values for a local module in a Root module c4-outputs.tf
  • Terraform Comamnd terraform get
  • Understand the differences between terraform init and terraform get

Step-02: Create Module Folder Structure

  • We are going to create modules folder and in that we are going to create a module named azure-static-website
  • We will copy required files from previous section for this respective module 50-Terraform-Azure-Static-Website\terraform-manifests.
  • Terraform Working Directory: 51-Terraform-Modules-Build-Local-Module\terraform-manifests
  • modules
  • Module-1: azure-static-website
  • main.tf
  • variables.tf
  • outputs.tf
  • README.md
  • LICENSE
  • Inside modules/azure-static-website, copy below listed three files from 50-Terraform-Azure-Static-Website\terraform-manifests
  • main.tf
  • variables.tf
  • outputs.tf
  • versions.tf

Step-03: Root Module: c1-versions.tf

  • Call Module from Terraform Work Directory
  • Create Terraform Configuration in Root Module by calling the newly created module
  • c1-versions.tf
  • c2-variables.tf
  • c3-static-website.tf
  • c4-outputs.tf
# Terraform Block
terraform {
  required_version = ">= 1.0.0"
  required_providers {
    azurerm = {
      source = "hashicorp/azurerm"
      version = ">= 2.0" 
    }    
  }
}

# Provider Block
provider "azurerm" {
 features {}          
}

Step-04: c2-variables.tf

  • Place holder file, if you want you can define variables.
  • For now focus is on Calling the Local Terraform Module in to Root Module so we are not going to complicate the stuff here.
  • We will leave this placeholder file

Step-05: c3-static-website.tf

  • Arguments for this module are going to be the variables defined in variables.tf of local module 
# Call our Custom Terraform Module which we built earlier
module "azure_static_website" {
  source = "./modules/azure-static-website"  # Mandatory

  # Resource Group
  location = "eastus"
  resource_group_name = "myrg1"

  # Storage Account
  storage_account_name = "staticwebsite"
  storage_account_tier = "Standard"
  storage_account_replication_type = "LRS"
  storage_account_kind = "StorageV2"
  static_website_index_document = "index.html"
  static_website_error_404_document = "error.html"
}

Step-06: c4-outputs.tf

  • Understand how we are going to reference the output values from a local module
  • The output names defined in local module outputs.tf will be the values in this c4-outputs.tf
# Output variable definitions
output "root_resource_group_id" {
  description = "resource group id"
  value       = module.azure_static_website.resource_group_id
}
output "root_resource_group_name" {
  description = "The name of the resource group"
  value       = module.azure_static_website.resource_group_name
}
output "root_resource_group_location" {
  description = "resource group location"
  value       = module.azure_static_website.resource_group_location
}
output "root_storage_account_id" {
  description = "storage account id"
  value       = module.azure_static_website.storage_account_id
}
output "root_storage_account_name" {
  description = "storage account name"
  value       = module.azure_static_website.storage_account_name
}

Step-07: Execute Terraform Commands

# Terraform Initialize
terraform init
Observation: 
1. Verify ".terraform", you will find "modules" folder in addition to "providers" folder
2. Verify inside ".terraform/modules" folder too.

# Terraform Validate
terraform validate

# Terraform Format
terraform fmt

# Terraform Plan
terraform plan

# Terraform Apply
terraform apply -auto-approve

# Upload Static Content
1. Go to Storage Accounts -> staticwebsitexxxxxx -> Containers -> $web
2. Upload files from folder "static-content"

# Verify 
1. Azure Storage Account created
2. Static Website Setting enabled
3. Verify the Static Content Upload Successful
4. Access Static Website: Goto Storage Account -> staticwebsitek123 -> Data Management -> Static Website
5. Get the endpoint name `Primary endpoint`
https://staticwebsitek123.z13.web.core.windows.net/

Step-08: Destroy and Clean-Up

# Terraform Destroy
terraform destroy -auto-approve

# Delete Terraform files 
rm -rf .terraform*
rm -rf terraform.tfstate*

Step-09: Understand terraform get command

  • We have used terraform init to download providers from terraform registry and at the same time to download modules present in local modules folder in terraform working directory.
  • Assuming we already have initialized using terraform init and later we have created module configs, we can terraform get to download the same.
  • Whenever you add a new module to a configuration, Terraform must install the module before it can be used.
  • Both the terraform get and terraform init commands will install and update modules.
  • The terraform init command will also initialize backends and install plugins.
# Delete modules in .terraform folder
ls -lrt .terraform/modules
rm -rf .terraform/modules
ls -lrt .terraform/modules

# Terraform Get
terraform get
ls -lrt .terraform/modules

Step10: Major difference between Local and Remote Module

  • When installing a remote module, Terraform will download it into the .terraform directory in your configuration's root directory.
  • When installing a local module, Terraform will instead refer directly to the source directory.
  • Because of this, Terraform will automatically notice changes to local modules without having to re-run terraform init or terraform get.