第五章：模块化

什么是模块？

模块是 Terraform 配置的可复用单元，用于组织和管理相关资源。

模块结构

modules/
└── vpc/
    ├── main.tf       # 主配置
    ├── variables.tf  # 输入变量
    ├── outputs.tf    # 输出值
    ├── versions.tf   # 版本约束
    └── README.md     # 文档

创建模块

variables.tf

# 输入变量
variable "name" {
  description = "VPC name"
  type        = string
}

variable "cidr" {
  description = "VPC CIDR block"
  type        = string
  default     = "10.0.0.0/16"
}

variable "azs" {
  description = "Availability zones"
  type        = list(string)
}

variable "public_subnets" {
  description = "Public subnet CIDR blocks"
  type        = list(string)
  default     = []
}

variable "private_subnets" {
  description = "Private subnet CIDR blocks"
  type        = list(string)
  default     = []
}

variable "enable_nat_gateway" {
  description = "Enable NAT Gateway"
  type        = bool
  default     = true
}

variable "tags" {
  description = "Tags for resources"
  type        = map(string)
  default     = {}
}

main.tf

# VPC
resource "aws_vpc" "main" {
  cidr_block           = var.cidr
  enable_dns_hostnames = true
  enable_dns_support   = true

  tags = merge(var.tags, {
    Name = var.name
  })
}

# 公有子网
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.azs[count.index]
  map_public_ip_on_launch = true

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

# 私有子网
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.azs[count.index]

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

# Internet Gateway
resource "aws_internet_gateway" "main" {
  vpc_id = aws_vpc.main.id

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

# NAT Gateway
resource "aws_eip" "nat" {
  count  = var.enable_nat_gateway ? 1 : 0
  domain = "vpc"

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

resource "aws_nat_gateway" "main" {
  count = var.enable_nat_gateway ? 1 : 0

  allocation_id = aws_eip.nat[0].id
  subnet_id     = aws_subnet.public[0].id

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

  depends_on = [aws_internet_gateway.main]
}

# 路由表
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block = "0.0.0.0/0"
    gateway_id = aws_internet_gateway.main.id
  }

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

resource "aws_route_table" "private" {
  count = var.enable_nat_gateway ? 1 : 0

  vpc_id = aws_vpc.main.id

  route {
    cidr_block     = "0.0.0.0/0"
    nat_gateway_id = aws_nat_gateway.main[0].id
  }

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

# 路由表关联
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_association" "private" {
  count = var.enable_nat_gateway ? length(var.private_subnets) : 0

  subnet_id      = aws_subnet.private[count.index].id
  route_table_id = aws_route_table.private[0].id
}

outputs.tf

output "vpc_id" {
  description = "VPC ID"
  value       = aws_vpc.main.id
}

output "vpc_cidr" {
  description = "VPC CIDR block"
  value       = aws_vpc.main.cidr_block
}

output "public_subnet_ids" {
  description = "Public subnet IDs"
  value       = aws_subnet.public[*].id
}

output "private_subnet_ids" {
  description = "Private subnet IDs"
  value       = aws_subnet.private[*].id
}

output "nat_gateway_id" {
  description = "NAT Gateway ID"
  value       = var.enable_nat_gateway ? aws_nat_gateway.main[0].id : null
}

output "internet_gateway_id" {
  description = "Internet Gateway ID"
  value       = aws_internet_gateway.main.id
}

versions.tf

terraform {
  required_version = ">= 1.0.0"

  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = ">= 4.0"
    }
  }
}

使用模块

本地模块

module "vpc" {
  source = "./modules/vpc"

  name            = "my-vpc"
  cidr            = "10.0.0.0/16"
  azs             = ["us-east-1a", "us-east-1b"]
  public_subnets  = ["10.0.1.0/24", "10.0.2.0/24"]
  private_subnets = ["10.0.3.0/24", "10.0.4.0/24"]

  tags = {
    Environment = "production"
  }
}

# 引用模块输出
resource "aws_instance" "web" {
  subnet_id = module.vpc.public_subnet_ids[0]
}

Terraform Registry 模块

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"

  name = "my-vpc"
  cidr = "10.0.0.0/16"

  azs             = ["us-east-1a", "us-east-1b"]
  private_subnets = ["10.0.1.0/24", "10.0.2.0/24"]
  public_subnets  = ["10.0.3.0/24", "10.0.4.0/24"]

  enable_nat_gateway = true

  tags = {
    Environment = "production"
  }
}

GitHub 模块

module "vpc" {
  source = "github.com/user/terraform-aws-vpc?ref=v1.0.0"

  name = "my-vpc"
  cidr = "10.0.0.0/16"
}

模块版本

版本约束

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"  # 5.x 最新版本
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = ">= 5.0.0, < 6.0.0"  # 5.x 范围
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "5.1.0"  # 精确版本
}

模块嵌套

# 模块调用其他模块
module "network" {
  source = "./modules/network"

  vpc_id = module.vpc.vpc_id
}

module "compute" {
  source = "./modules/compute"

  subnet_ids = module.vpc.private_subnet_ids
}

模块最佳实践

1. 标准结构

modules/
└── my-module/
    ├── main.tf       # 主配置
    ├── variables.tf  # 输入变量
    ├── outputs.tf    # 输出值
    ├── versions.tf   # 版本约束
    ├── README.md     # 文档
    └── examples/
        └── basic/
            ├── main.tf
            └── outputs.tf

2. 变量验证

variable "instance_type" {
  description = "EC2 instance type"
  type        = string

  validation {
    condition     = contains(["t3.micro", "t3.small", "t3.medium"], var.instance_type)
    error_message = "Instance type must be t3.micro, t3.small, or t3.medium."
  }
}

3. 默认值

variable "tags" {
  description = "Tags for resources"
  type        = map(string)
  default     = {}
}

# 使用时合并
tags = merge(var.tags, {
  ManagedBy = "terraform"
})

4. 输出文档

output "vpc_id" {
  description = "The ID of the VPC"
  value       = aws_vpc.main.id
}

5. README 文档

# VPC Module

## Description
Creates a VPC with public and private subnets.

## Usage

```hcl
module "vpc" {
  source = "./modules/vpc"

  name            = "my-vpc"
  cidr            = "10.0.0.0/16"
  azs             = ["us-east-1a", "us-east-1b"]
  public_subnets  = ["10.0.1.0/24", "10.0.2.0/24"]
  private_subnets = ["10.0.3.0/24", "10.0.4.0/24"]
}

Inputs

Name	Description	Type	Default
name	VPC name	string	-
cidr	VPC CIDR	string	"10.0.0.0/16"

Outputs

Name	Description
vpc_id	VPC ID
public_subnet_ids	Public subnet IDs
```

小结

本章学习了：

• ✅ 模块概念和结构
• ✅ 创建模块
• ✅ 使用模块
• ✅ 模块版本管理
• ✅ 模块最佳实践

下一章

第六章：多云部署 - 学习多云架构部署。