terraform-dependency-analyzer

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Terraform Dependency Analyzer

Terraform依赖分析工具

This skill helps analyze and optimize resource dependencies in Terraform configurations.

此技能可帮助分析和优化Terraform配置中的资源依赖关系。

When to Use

使用场景

Use this skill when:

Understanding resource relationships and dependencies
Troubleshooting circular dependency errors
Optimizing resource creation order
Refactoring complex configurations
Documenting infrastructure dependencies

以下场景可使用此技能：

理解资源关系与依赖
排查循环依赖错误
优化资源创建顺序
重构复杂配置
记录基础设施依赖

Dependency Types

依赖类型

Implicit Dependencies

隐式依赖

Terraform automatically detects dependencies through resource attribute references:

Most common and preferred method
Created when one resource references another's attributes
Example:
```
subnet_id = aws_subnet.main.id
```

Terraform会通过资源属性引用自动检测依赖：

最常见且推荐的方式
当一个资源引用另一个资源的属性时自动创建
示例：
```
subnet_id = aws_subnet.main.id
```

Explicit Dependencies

显式依赖

Use

depends_on

only when implicit dependencies aren't sufficient:

Cross-resource timing requirements
Dependencies not expressed through attributes
Ensuring proper creation/deletion order
Should be used sparingly

仅当隐式依赖无法满足需求时，才使用

depends_on

：

跨资源的时序要求
无法通过属性表达的依赖
确保正确的创建/删除顺序
应谨慎使用

Analysis Workflow

分析流程

1. Generate Dependency Graph

1. 生成依赖图

bash

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bash

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Create visual dependency graph

创建可视化依赖图

terraform graph | dot -Tpng > graph.png

View as text

以文本形式查看

terraform graph

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terraform graph

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2. Identify Resource Relationships

2. 识别资源关系

Parse configuration to map dependencies:

Read through resource definitions
Note attribute references between resources
Identify explicit
```
depends_on
```
declarations
Map out dependency chains

解析配置以映射依赖关系：

通读资源定义
记录资源间的属性引用
识别显式的
```
depends_on
```
声明
梳理依赖链

3. Check for Circular Dependencies

3. 检查循环依赖

Common causes:

Security groups with mutual ingress rules
Resources referencing each other's attributes
Module outputs creating circular references

Solution approaches:

Break cycles using separate rule resources
Restructure resource relationships
Use data sources to break circular references

常见原因：

包含相互入站规则的安全组
资源间互相引用属性
模块输出导致的循环引用

解决方法：

使用独立的规则资源打破循环
重构资源关系
使用数据源打破循环引用

Common Dependency Patterns

常见依赖模式

VPC Infrastructure

VPC基础设施

VPC → Internet Gateway, Subnets
Subnets → NAT Gateway, Route Tables
Route Tables → Route Table Associations
Security Groups → EC2/RDS instances

VPC → 互联网网关、子网
子网 → NAT网关、路由表
路由表 → 路由表关联
安全组 → EC2/RDS实例

IAM Resources

IAM资源

IAM Role → IAM Policy Attachments
IAM Role → Resources using the role

IAM角色 → IAM策略关联
IAM角色 → 使用该角色的资源

Database Setup

数据库配置

VPC, Subnets → DB Subnet Group
Security Group → RDS Instance
RDS Instance → Application resources

VPC、子网 → 数据库子网组
安全组 → RDS实例
RDS实例 → 应用资源

Troubleshooting

故障排查

Circular Dependency Errors

循环依赖错误

Process:

Identify the resources in the cycle from error message
Determine which reference creates the cycle
Break the cycle by:
- Using separate rule resources (for security groups)
- Restructuring resource relationships
- Using data sources instead of direct references

排查流程：

从错误信息中识别循环中的资源
确定是哪个引用导致了循环
通过以下方式打破循环：
- 使用独立的规则资源（针对安全组）
- 重构资源关系
- 使用数据源替代直接引用

Slow Apply Times

执行速度缓慢

Analysis:

Check for unnecessary
```
depends_on
```
statements forcing sequential creation
Identify resources that could be created in parallel
Look for bottleneck resources blocking multiple dependencies

Optimization:

Remove explicit dependencies when implicit ones exist
Group independent resources together
Use modules to organize related resources

分析：

检查是否存在不必要的
```
depends_on
```
语句强制资源按顺序创建
识别可并行创建的资源
寻找阻塞多个依赖的瓶颈资源

优化方案：

当存在隐式依赖时，移除显式依赖
将独立资源分组
使用模块组织相关资源

Optimization Guidelines

优化指南

Minimize Explicit Dependencies

减少显式依赖

Prefer implicit dependencies through attribute references
Only use
```
depends_on
```
when absolutely necessary
Remove redundant explicit dependencies

优先使用通过属性引用的隐式依赖
仅在绝对必要时使用
```
depends_on
```
移除冗余的显式依赖

Maximize Parallelization

最大化并行化

Ensure independent resources have no unnecessary dependencies
Group related resources in modules
Avoid creating artificial dependency chains

确保独立资源没有不必要的依赖
将相关资源分组到模块中
避免创建人为的依赖链

Use Modules Effectively

高效使用模块

Organize resources by logical grouping
Use module outputs to express dependencies
Keep module dependencies clear and minimal

按逻辑分组组织资源
使用模块输出表达依赖
保持模块依赖清晰且精简

Analysis Checklist

分析检查清单

Generated dependency graph
Identified all resource relationships
Checked for circular dependencies
Verified implicit dependencies are sufficient
Removed unnecessary
```
depends_on
```
statements
Identified opportunities for parallelization
Documented critical dependency chains