terraform-module-builder

Terraform Module Builder

Build reusable, production-ready Terraform modules for cloud infrastructure.

Core Workflow

1. Define module structure: Organize files properly
2. Declare variables: Input parameters with validation
3. Create resources: Infrastructure definitions
4. Configure outputs: Export useful values
5. Setup state: Remote backend configuration
6. Document: README and examples

Module Structure

modules/
└── vpc/
    ├── main.tf           # Primary resources
    ├── variables.tf      # Input variables
    ├── outputs.tf        # Output values
    ├── versions.tf       # Provider versions
    ├── locals.tf         # Local values
    ├── data.tf           # Data sources
    ├── README.md         # Documentation
    └── examples/
        └── complete/
            ├── main.tf
            └── outputs.tf

VPC Module Example

Main Configuration

# modules/vpc/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(
    var.tags,
    {
      Name = var.name
    }
  )
}

resource "aws_internet_gateway" "main" {
  count = var.create_igw ? 1 : 0

  vpc_id = aws_vpc.main.id

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-igw"
    }
  )
}

resource "aws_subnet" "public" {
  count = length(var.public_subnets)

  vpc_id                  = aws_vpc.main.id
  cidr_block              = var.public_subnets[count.index]
  availability_zone       = var.availability_zones[count.index]
  map_public_ip_on_launch = true

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-public-${var.availability_zones[count.index]}"
      Tier = "public"
    }
  )
}

resource "aws_subnet" "private" {
  count = length(var.private_subnets)

  vpc_id            = aws_vpc.main.id
  cidr_block        = var.private_subnets[count.index]
  availability_zone = var.availability_zones[count.index]

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-private-${var.availability_zones[count.index]}"
      Tier = "private"
    }
  )
}

resource "aws_eip" "nat" {
  count = var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.public_subnets)) : 0

  domain = "vpc"

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-nat-${count.index + 1}"
    }
  )

  depends_on = [aws_internet_gateway.main]
}

resource "aws_nat_gateway" "main" {
  count = var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.public_subnets)) : 0

  allocation_id = aws_eip.nat[count.index].id
  subnet_id     = aws_subnet.public[count.index].id

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-nat-${count.index + 1}"
    }
  )

  depends_on = [aws_internet_gateway.main]
}

resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-public-rt"
    }
  )
}

resource "aws_route" "public_internet" {
  count = var.create_igw ? 1 : 0

  route_table_id         = aws_route_table.public.id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.main[0].id
}

resource "aws_route_table_association" "public" {
  count = length(var.public_subnets)

  subnet_id      = aws_subnet.public[count.index].id
  route_table_id = aws_route_table.public.id
}

resource "aws_route_table" "private" {
  count = var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.private_subnets)) : 0

  vpc_id = aws_vpc.main.id

  tags = merge(
    var.tags,
    {
      Name = "${var.name}-private-rt-${count.index + 1}"
    }
  )
}

resource "aws_route" "private_nat" {
  count = var.enable_nat_gateway ? (var.single_nat_gateway ? 1 : length(var.private_subnets)) : 0

  route_table_id         = aws_route_table.private[count.index].id
  destination_cidr_block = "0.0.0.0/0"
  nat_gateway_id         = aws_nat_gateway.main[var.single_nat_gateway ? 0 : count.index].id
}

resource "aws_route_table_association" "private" {
  count = length(var.private_subnets)

  subnet_id      = aws_subnet.private[count.index].id
  route_table_id = aws_route_table.private[var.single_nat_gateway ? 0 : count.index].id
}