Using Terragrunt to Reduce Terraform Code Redundancy and Accelerate Infrastructure Deployment

In this tutorial we explore Terragrunt, an open‑source command‑line wrapper for Terraform that helps reduce code duplication and manage remote state, making large‑scale infrastructure projects easier to maintain.

Terraform Issues

Repeated versions.tf code

Duplicated module imports

Backend configuration duplication

Provider configuration duplication

Terragrunt Overview

Terragrunt, maintained by Gruntwork, acts as a wrapper around Terraform, allowing remote state management and module orchestration while keeping Terraform logic separate from its implementation. By replacing *.tf files with terragrunt.hcl files, inputs can be passed to modules from any environment.

Using Terragrunt to Optimize Terraform Code

We first create a module named module-alicloud-dns in the repository and reference it from various environments.

provider "alicloud" {
  region = "cn-beijing"
}

## oss
resource "alicloud_oss_bucket" "tfbucket" {
  bucket = "tf-backend-datas"
  acl    = "private"
}

## tablestore
resource "alicloud_ots_instance" "tftable" {
  name        = "tftablenew"
  description = "terraform tablestore"
  accessed_by = "Any"
  tags = {
    Created = "TF"
    For     = "Building table"
  }
}

resource "alicloud_ots_table" "basic" {
  instance_name = alicloud_ots_instance.tftable.name
  table_name    = "myterraformtable"
  primary_key {
    name = "LockID"
    type = "String"
  }
  time_to_live = -1
  max_version  = 1
  deviation_cell_version_in_sec = 1
}

Deploy the backend using Terraform commands:

terraform init
terraform plan
terraform apply --auto-approve

Convert the local state to OSS by adding backend.tf and re‑initialising:

terraform {
  backend "oss" {
    bucket               = "tf-backend-datas"
    prefix               = "global/backend"
    key                  = "terraform-global-backend.tfstate"
    region               = "cn-beijing"
    tablestore_endpoint  = "https://tftablenew.cn-beijing.ots.aliyuncs.com"
    tablestore_table    = "myterraformtable"
  }
}

Deploy Dev Environment

Enter the dev directory, verify that backend.tf matches the backend configuration, then run:

terraform init
terraform plan
terraform apply --auto-approve

Verification is performed in the Alibaba Cloud console.

Terragrunt Configuration Files

Root terragrunt.hcl defines provider, Terraform version, module source, and remote state:

// define provider
generate "provider" {
  path      = "provider.tf"
  if_exists = "overwrite_terragrunt"
  contents   = <

Environment‑Specific Inheritance

Dev environment terragrunt.hcl inherits the root configuration and supplies inputs:

include "root" {
  path = find_in_parent_folders()
}

inputs = {
  dns_zone_name = "zeyang.site"
  dns_record    = "tgdev"
  eip           = "123.123.123.123"
  record_type   = "A"
}

Run:

terragrunt init
terragrunt plan
terragrunt apply

Similar stg configuration inherits the root and provides its own inputs.

Summary

Terragrunt helps reduce Terraform code redundancy by centralising provider, backend, version, and module definitions, enabling clean multi‑environment deployments and simplifying infrastructure‑as‑code management on Alibaba Cloud.