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https://github.com/cisco-open/stacks
Stacks, the Terraform code pre-processor
https://github.com/cisco-open/stacks
terraform
Last synced: about 1 month ago
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Stacks, the Terraform code pre-processor
- Host: GitHub
- URL: https://github.com/cisco-open/stacks
- Owner: cisco-open
- License: apache-2.0
- Created: 2023-03-15T20:40:01.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-06-26T23:22:07.000Z (6 months ago)
- Last Synced: 2024-08-02T00:26:36.617Z (4 months ago)
- Topics: terraform
- Language: Python
- Homepage:
- Size: 200 KB
- Stars: 147
- Watchers: 6
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project
- awesome-tf - stacks - Stacks, the Terraform code pre-processor (Tools / Community providers)
- jimsghstars - cisco-open/stacks - Stacks, the Terraform code pre-processor (Python)
README
## What is Stacks for Terraform?
**Stacks** is a code pre-processor for Terraform. It implements a **sustainable scaling pattern**, **prevents drift** and **boilerplate**, all while **plugging into your already existing Terraform pipeline**.
Stacks was initially presented at [SREcon23 Americas](https://www.usenix.org/conference/srecon23americas/presentation/bejarano).
***Warning:** Stacks is under heavy development, many things may change.*
## What is a "stack"?
- A **stack** is a set of Terraform resources you want to deploy one or more times.
- Each instance of a stack is a **layer**. A stack has one or more layers, hence, the name "stacks".
### Example
```
vpc/
│
├── base/
│ ├── vpc.tf
│ └── subnets.tf
│
├── layers/
│ ├── production/
│ │ └── layer.tfvars
│ └── staging/
│ ├── layer.tfvars
│ └── vpn.tf
│
└── stack.tfvars
```
- This is an example stack called `vpc`.
- It contains a `base` folder, containing the common Terraform configuration scoped for all layers in this stack.
- It contains a `layers` folder with two layers, one called `production` and one called `staging`. Layer directories contain layer-specific Terraform configuration.
- Finally, it contains an optional `stack.tfvars` file, which defines variables global to all layers in the stack. These variables can be overriden at the layer level through a layer-specific `layer.tfvars`.
## How does Stacks work?
Stacks sits between you (the Terraform user) and Terraform. It's a **code pre-processor**.
Here's an overview of Stacks inner workings:
1. It takes your stack definitions (as shown above)
1. For each layer:
1. Joins the `base` code with the layer-specific code
1. Applies a number of transformations
1. Injects some extra configuration
1. Bundles it up for Terraform to plan/apply on it
## How to use Stacks?
First, you need to put the Stacks code somewhere close to your stack definitions.
Here's an example (not necessarily what we recommend):
```
your-terraform-repository/
│
├── src/ # the contents of the `src` directory
│ ├── helpers.py
│ ├── postinit.py
│ └── preinit.py
│
├── environments/ # see the `example` directory on how to set this up
│ ├── production/
│ │ ├── backend.tfvars
│ │ └── environment.tfvars
│ └── staging/
│
└── stacks/ # put your stack definitions here
└── vpc/ # the `vpc` stack shown above
├── base/
│ ├── vpc.tf
│ └── subnets.tf
├── layers/
│ ├── production/
│ │ └── layer.tfvars
│ └── staging/
│ ├── layer.tfvars
│ └── vpn.tf
└── stack.tfvars
```
You can find [another example here](example/stacks/example) with all the appropriate file contents.
Then you need to run Stacks in the layer you want to apply:
```bash
cd stacks/vpc/layers/production
python3 ../../../../src/preinit.py
cd stacks.out # where the preinit output goes
terraform init
python3 ../../../../../src/postinit.py
```
Now you're ready to run any further `terraform` commands in the `stacks.out` directory.
***Note:** we recommend putting `stacks.out` in `.gitignore` to prevent it from being tracked by git.*
