Infrastructure as Code (IaC) has revolutionized how organizations provision and manage their cloud and on-premise resources. Terraform, as one of the most widely adopted IaC tools, enables developers to define infrastructure declaratively. However, as infrastructure scales and complexity grows, managing Terraform configurations across multiple environments, modules, and dependencies can become cumbersome.
To address these challenges, Terraform Stacks introduce a higher-level abstraction that simplifies the organization, deployment, and scaling of infrastructure components. In this guide, we will explore the concept of Terraform Stacks, why they are necessary, how they work, their benefits, and a step-by-step implementation process.
Why Terraform Stacks? Addressing Infrastructure Management Challenges
When working with Terraform at scale, organizations often split infrastructure into multiple modules and workspaces to enhance composability and reusability. While this approach is beneficial, it presents several challenges:
- Dependency Management: Coordinating dependencies between multiple modules can be complex, especially when modules need to be deployed in a specific order.
- Configuration Consistency: Maintaining a uniform configuration across multiple environments (e.g., development, staging, production) requires significant effort.
- Operational Overhead: As the number of Terraform configurations grows, managing multiple workspaces and deployments becomes overwhelming.
Terraform Stacks solve these problems by introducing a structured, scalable, and reusable approach to infrastructure provisioning. They provide a way to group related infrastructure components into cohesive units while maintaining flexibility in deployments.
Understanding Terraform Stacks: Core Concepts
A Terraform Stack is a logical unit that organizes infrastructure components into a structured configuration. It consists of two key files:
1. Component Configuration (.tfstack.hcl)
This file defines what infrastructure components are part of the stack. It acts as a blueprint, specifying:
- Modules: Pre-defined Terraform modules that are reused within the stack.
- Configuration Variables: Input values required by the modules.
- Dependencies: Links between different components that require a specific deployment order.
The component configuration ensures that modules remain reusable across multiple environments while maintaining a centralized definition for infrastructure components.
component "networking" {
source = "terraform-aws-modules/vpc/aws"
inputs = {
aws_region = var.aws_region
cluster_name_prefix = var.prefix
instance_type = "t2.medium"
}
providers = {
aws = provider.aws.this
random = provider.random.this
tls = provider.tls.this
cloudinit = provider.cloudinit.this
}
}
component "database" {
source = "terraform-aws-modules/rds/aws"
inputs = {
aws_region = var.aws_region
cluster_name_prefix = var.prefix
instance_type = "t2.medium"
}
providers = {
aws = provider.aws.this
random = provider.random.this
tls = provider.tls.this
cloudinit = provider.cloudinit.this
}
}
2. Deployment Configuration (.tfdeploy.hcl)
This file defines how and where the stack will be deployed. It specifies:
- Target Environments: Defines deployment destinations such as AWS accounts, Kubernetes clusters, or cloud regions.
- Instance Count: Determines how many times the stack should be deployed.
- Custom Parameters: Allows environment-specific overrides, such as different database sizes for staging vs. production.
The deployment configuration allows infrastructure teams to scale infrastructure dynamically by managing multiple instances of a stack from a single configuration.
deployment "staging" {
inputs = {
aws_region = "us-west-1"
instance_count = 1
}
}
deployment "production" {
inputs = {
aws_region = "eu-west-1"
instance_count = 1
}
}
3. Deployment Configuration Orchestration Rule
Written in HCL, Orchestration rules enable users to automate repetitive tasks within Stacks. With the public beta release, users can configure auto-approval for plans when specific orchestration conditions are satisfied. For instance, the following orchestrate block ensures automatic approval of deployments as long as no resources are scheduled for removal in the plan.
orchestrate "auto_approve" “safe_plans” {
check {
#check that there are no resources being removed
condition = context.plan.changes.remove == 0
reason = "Plan has ${context,plan.changes. remove} resources to be removed."
}
}
The following repositories contains sample code that can applied to help deepen the understanding and application of Terraform Stacks
- https://github.com/shernandez5/eks-deferred-stack-demo
- https://github.com/shernandez5/lambda-component-expansion-stack
Key Benefits of Terraform Stacks
Using Terraform Stacks introduces a more structured and scalable approach to managing infrastructure. Here’s why organizations should adopt them:
1. Simplified Infrastructure Management
Stacks group related resources together, reducing the cognitive load of managing multiple Terraform configurations separately. Teams can focus on higher-level infrastructure design instead of dealing with individual module dependencies manually.
2. Enhanced Reusability
Instead of writing repetitive configurations for different environments, Terraform Stacks enable modular reuse of infrastructure definitions. Organizations can maintain a single source of truth while deploying the same stack to different environments.
3. Seamless Scalability
The deployment configuration allows infrastructure teams to define scalable architectures, supporting multiple deployments across various cloud providers or on-premise environments with minimal changes.
4. Improved Consistency Across Environments
Stacks enforce standardized configurations, reducing configuration drift between development, staging, and production environments. This ensures predictable and reliable infrastructure deployments.
5. Reduced Operational Overhead
Instead of managing infrastructure as separate Terraform configurations, stacks provide a centralized way to apply changes across multiple deployments, reducing manual effort.
Future of Terraform Stacks
HashiCorp is continuously enhancing Terraform Stacks to simplify large-scale infrastructure management further. Future developments may include:
- Improved Dependency Management: More automation for handling interdependent module deployments.
- Enhanced Observability: Tools to track and visualize stack deployments across multiple environments.
- Deeper Integration with CI/CD Pipelines: Automating stack deployments as part of DevOps workflows.
As organizations adopt Infrastructure as Code at scale, Terraform Stacks will play a crucial role in enabling modular, reusable, and efficient cloud provisioning.
Conclusion
Terraform Stacks introduce a structured, scalable, and reusable approach to managing cloud and on-premise infrastructure. By grouping related resources, defining centralized configurations, and providing scalable deployment strategies, they reduce operational complexity and improve infrastructure consistency.
For organizations looking to optimize their Terraform workflows, adopting Terraform Stacks can lead to greater efficiency, better maintainability, and improved scalability in infrastructure provisioning. The following video also explains a demonstration of Terraform Stacks.
