Terraform Patterns

Terraform IaC Patterns

Core Concepts

Terraform is a declarative tool for provisioning infrastructure. Instead of writing scripts to create servers, you define the desired state, and Terraform executes the API calls to make reality match the state.

1. State Management (.tfstate)

Terraform maps real-world resources to your configuration using a state file. For teams, state MUST be stored remotely (e.g., AWS S3, Terraform Cloud) to avoid conflicts and loss.

• State Locking: Use DynamoDB tables alongside S3 to "lock" the state file, preventing two developers from running terraform apply simultaneously and corrupting infrastructure.

2. Modules (DRY Principle)

Encapsulate complex resource combinations (VPC + Subnets + NatGateway) into reusable modules. Consume modules using variables.

Terraform Lifecycle Map

%%{init: {"theme": "default", "flowchart": {"useMaxWidth": true}}}%%
flowchart TD
    subgraph Local ["Developer Workspace"]
        A["Write HCL Code (.tf)"]
        B["terraform init"]
        C["terraform plan"]
        D["terraform apply"]
    end
    
    subgraph Backend ["Remote State Backend"]
        E["State File (.tfstate in S3)"]
        F["State Lock (DynamoDB)"]
    end
    
    subgraph Cloud ["Cloud Provider (AWS/GCP)"]
        G["Cloud API (Create/Update/Delete)"]
        H["Provisioned Resources"]
    end
    
    B -.->|"Downloads Providers"| A
    C -->|"Reads State"| E
    C -->|"Acquires Lock"| F
    D -->|"Executes"| G
    G -->|"Manages"| H
    D -->|"Writes Updated State"| E