structure

Understanding the directory structure

.
├── definitions
│   ├── resourse01
│   │   ├── main.tf
│   │   └── variables.tf
│   ├── resourse02
│   │   ├── main.tf
│   │   └── variables.tf
│   ├── resourse03
│   │   ├── main.tf
│   │   └── variables.tf
└── env
    ├── common.hcl
    ├── terragrunt.hcl
    ├── stage
    │   ├── credentials.json
    │   ├── env.hcl
    │   ├── regionA
    │   │   ├── resourse01
    │   │   │   └── terragrunt.hcl
    │   │   ├── resource04
    │   │   │   ├── main.tf
    │   │   │   ├── terragrunt.hcl
    │   │   │   └── variables.tf
    │   │   ├── region.hcl
    │   ├── global
    │   │   ├── resourse02
    │   │   │   └── terragrunt.hcl
    │   │   └── region.hcl
    │   └── regionB
    │       ├── resource03
    │       │   └── terragrunt.hcl
    │       └── region.hcl
    ├── prod
    │   └── ...

• ./definitions/ => All the resources which has same definition across the environments stay here. They will have independent hcl config file in respective ./env/ directory. In above directory structure resource 01, 02 and 03 have same definition but different configuration accross the environments.
• ./env/common.hcl => Common variables that apply across environments stay here.
• ./env/terragrunt.hcl => Declarations for remote state and providers stay here.
• ./env/stage => Root directory for all configurations controlled by environment stage.
• ./env/stage/env.hcl => Configurations limited to environment stage are declared here.
• ./env/stage/region/ => Root directory for all resource configurations for given region. In above directory structure region A and B are digfferent regions.
• ./env/stage/global => All the resources which are not bounded to any region stays here.
• ./env/stage/regionA/resource04 => This is a example resource which is not having standard definition across environments and hence it's definition is stored directly in to the stage directory. Similiarly prod version of resource04 needs to be defined ar path ./env/prod/regionA/resource04

Preparation to get going

• State of cloud infrastructure will be stored in backend file in Google Cloud bucket. Create bucket with name as required in file ./env/terragrunt.hcl

Terragrunt plan & apply

This project works with Terragrunt. Run following commands from root directory of required environment. e.g. for stage environment it would be ./env/stage/. Commands can be run for individual resource group as well. e.g ./env/stage/regionA/resource01/.

# Plan all resources in resource01
$ /env/stage/regionA/resource01/ terragrunt plan-all 

# Plan all resources in regionA
$ /env/stage/regionA/ terragrunt plan-all

Plan all resources in env stage
$ /env/stage/ terragrunt plan-all

Plan all resources across the environments 
$ /env/ terragrunt plan-all

Terragrunt plan & apply

Similiarly, final make the changes with apply command.

terragrunt apply-all

Terragrunt destroy

Undone infra changes by using following command. This will destroy actual infra.

terragrunt destroy-all