terraform-module-library

• The task is unrelated to terraform module library
• You need a different domain or tool outside this scope

• Clarify goals, constraints, and required inputs.
• Apply relevant best practices and validate outcomes.
• Provide actionable steps and verification.
• If detailed examples are required, open resources/implementation-playbook.md.

Create reusable, well-tested Terraform modules for common cloud infrastructure patterns across multiple cloud providers.

• Build reusable infrastructure components
• Standardize cloud resource provisioning
• Implement infrastructure as code best practices
• Create multi-cloud compatible modules
• Establish organizational Terraform standards

```

terraform-modules/

├── aws/

│ ├── vpc/

│ ├── eks/

│ ├── rds/

│ └── s3/

├── azure/

│ ├── vnet/

│ ├── aks/

│ └── storage/

└── gcp/

├── vpc/

├── gke/

└── cloud-sql/

```

```

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.go

```

main.tf:

```hcl

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:

```hcl

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:

```hcl

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

}

```

1. Use semantic versioning for modules
2. Document all variables with descriptions
3. Provide examples in examples/ directory
4. Use validation blocks for input validation
5. Output important attributes for module composition
6. Pin provider versions in versions.tf
7. Use locals for computed values
8. Implement conditional resources with count/for_each
9. Test modules with Terratest
10. Tag all resources consistently

```hcl

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"

}

}

```

• assets/vpc-module/ - Complete VPC module example
• assets/rds-module/ - RDS module example
• references/aws-modules.md - AWS module patterns
• references/azure-modules.md - Azure module patterns
• references/gcp-modules.md - GCP module patterns

```go

// 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)

}

```

• multi-cloud-architecture - For architectural decisions
• cost-optimization - For cost-effective designs