SKILL.md
Terraform Module Library
Production-ready Terraform module patterns for AWS, Azure, GCP, and OCI infrastructure.
Purpose
Create reusable, well-tested Terraform modules for common cloud infrastructure patterns across multiple cloud providers.
When to Use
- Build reusable infrastructure components
- Standardize cloud resource provisioning
- Implement infrastructure as code best practices
- Create multi-cloud compatible modules
- Establish organizational Terraform standards
Module Structure
terraform-modules/
├── aws/
│ ├── vpc/
│ ├── eks/
│ ├── rds/
│ └── s3/
├── azure/
│ ├── vnet/
│ ├── aks/
│ └── storage/
├── gcp/
│ ├── vpc/
│ ├── gke/
│ └── cloud-sql/
└── oci/
├── vcn/
├── oke/
└── object-storage/Standard Module Pattern
module-name/
├── main.tf # Main resources
├── variables.tf # Input variables
├── outputs.tf # Output values
├── versions.tf # Provider versions
├── README.md # Documentation
├── examples/ # Usage examples
│ └── complete/
│ ├── main.tf
│ └── variables.tf
└── tests/ # Terratest files
└── module_test.goAWS VPC Module Example
main.tf:
resource "aws_vpc" "main" {
cidr_block = var.cidr_block
enable_dns_hostnames = var.enable_dns_hostnames
enable_dns_support = var.enable_dns_support
tags = merge(
{
Name = var.name
},
var.tags
)
}
resource "aws_subnet" "private" {
count = length(var.private_subnet_cidrs)
vpc_id = aws_vpc.main.id
cidr_block = var.private_subnet_cidrs[count.index]
availability_zone = var.availability_zones[count.index]
tags = merge(
{
Name = "${var.name}-private-${count.index + 1}"
Tier = "private"
},
var.tags
)
}
resource "aws_internet_gateway" "main" {
count = var.create_internet_gateway ? 1 : 0
vpc_id = aws_vpc.main.id
tags = merge(
{
Name = "${var.name}-igw"
},
var.tags
)
}variables.tf:
variable "name" {
description = "Name of the VPC"
type = string
}
variable "cidr_block" {
description = "CIDR block for VPC"
type = string
validation {
condition = can(regex("^([0-9]{1,3}\\.){3}[0-9]{1,3}/[0-9]{1,2}$", var.cidr_block))
error_message = "CIDR block must be valid IPv4 CIDR notation."
}
}
variable "availability_zones" {
description = "List of availability zones"
type = list(string)
}
variable "private_subnet_cidrs" {
description = "CIDR blocks for private subnets"
type = list(string)
default = []
}
variable "enable_dns_hostnames" {
description = "Enable DNS hostnames in VPC"
type = bool
default = true
}
variable "tags" {
description = "Additional tags"
type = map(string)
default = {}
}outputs.tf:
output "vpc_id" {
description = "ID of the VPC"
value = aws_vpc.main.id
}
output "private_subnet_ids" {
description = "IDs of private subnets"
value = aws_subnet.private[*].id
}
output "vpc_cidr_block" {
description = "CIDR block of VPC"
value = aws_vpc.main.cidr_block
}Best Practices
- Use semantic versioning for modules
- Document all variables with descriptions
- Provide examples in examples/ directory
- Use validation blocks for input validation
- Output important attributes for module composition
- Pin provider versions in versions.tf
- Use locals for computed values
- Implement conditional resources with count/for_each
- Test modules with Terratest
- Tag all resources consistently
Reference: See references/aws-modules.md and references/oci-modules.md
Module Composition
module "vpc" {
source = "../../modules/aws/vpc"
name = "production"
cidr_block = "10.0.0.0/16"
availability_zones = ["us-west-2a", "us-west-2b", "us-west-2c"]
private_subnet_cidrs = [
"10.0.1.0/24",
"10.0.2.0/24",
"10.0.3.0/24"
]
tags = {
Environment = "production"
ManagedBy = "terraform"
}
}
module "rds" {
source = "../../modules/aws/rds"
identifier = "production-db"
engine = "postgres"
engine_version = "15.3"
instance_class = "db.t3.large"
vpc_id = module.vpc.vpc_id
subnet_ids = module.vpc.private_subnet_ids
tags = {
Environment = "production"
}
}Testing
// tests/vpc_test.go
package test
import (
"testing"
"github.com/gruntwork-io/terratest/modules/terraform"
"github.com/stretchr/testify/assert"
)
func TestVPCModule(t *testing.T) {
terraformOptions := &terraform.Options{
TerraformDir: "../examples/complete",
}
defer terraform.Destroy(t, terraformOptions)
terraform.InitAndApply(t, terraformOptions)
vpcID := terraform.Output(t, terraformOptions, "vpc_id")
assert.NotEmpty(t, vpcID)
}Related Skills
multi-cloud-architecture- For architectural decisions
cost-optimization- For cost-effective designs