Unlock the Power of Terragrunt’s Hierarchy

In this article, readers will learn about Terragrunt (associated with Terraform) and how to unlock the power of Terragrunt’s hierarchy, including code.

Developers have many options to build a cloud environment using available tools, but today’s complex infrastructure involves numerous interconnected services and processes. To ensure smooth operation amidst daily changes in your production environment, it is crucial to use advanced tools to design and build an elastic cloud environment. These tools can simplify coding and prevent repetitive tasks for you and your team.

Here are some tips that will simplify the code for you and prevent repetition from you and the rest of the team:

Get to Know the Terraform Tool

Terraform is a tool that enables developers to define the architecture of their infrastructure through a clear and readable file format known as HCL. This file format describes the elastic components of the infrastructure, such as VPCs, Security Groups, Load Balancers, and more. It provides a simple and concise way to define the topology of the development environment.

Two Major Challenges When Designing Automated Cloud Environments

The first challenge arises during the initial run, when there is little or no interdependence between the different resources. This is relatively easy to handle.
The second challenge is more complex and occurs when new resources need to be developed, updated, or deleted in an existing cloud environment that is constantly changing.

In a cloud environment, changes should be carefully planned and executed to minimize errors between teams and ensure a smooth and efficient implementation. To achieve this, simplification of the cloud environment is crucial to prevent code duplication among developers working on the same source code.

How Terragrunt Solves This Problem: An In-Depth Look

Terragrunt is a tool that enhances Terraform’s functionality by providing additional infrastructure management tools that help maintain a DRY (Don’t Repeat Yourself) code base, dressing up existing Terraform modules and managing the remote state of the cloud environment.

An example where Terragrunt can be particularly useful is in a distributed cloud environment where multiple resources share the same values, such as subnets and security groups. Without proper management, developers may inadvertently duplicate these values, leading to errors and inconsistencies. Terragrunt helps prevent code duplication by allowing the parameters to be defined only once, ensuring there is no confusion about the shared parameters in the environment.

To optimize performance, Terragrunt enforces specific development principles and restrictions on the organization of Terraform code:

Terragrunt mandates the use of a hierarchical folder structure to maintain consistency and prevent errors in the Terraform code.
Terragrunt promotes centralized file management for shared common variables, enabling the organization of code and changes in a single location.

Optimizing Cloud Environments With Logical Organization Using Terragrunt

Before using Terragrunt, it is essential to organize the logical environment by dividing it into smaller scopes through folders. This approach enables the reuse of resources and modules without the need for rewriting –> promoting efficiency and reducing the risk of errors.

By organizing the workspace in this manner, Terragrunt allows for the import of entries from Terragrunt.hcl files located in other hierarchies within the cloud environment. This process avoids duplicating values required for different resources by using the “Include Block” or “Dependency Block” to import previously written values from other hierarchies in the environment.

Efficient File Management in Shared Spaces for Improved Collaboration

Terragrunt offers a powerful capability for sharing configuration files with ease. Much like Terraform, Terragrunt receives parameters to launch resources. However, unlike Terraform, Terragrunt allows to define these parameters at a higher level, so different resources within the environment can make use of the same parameters.

For instance, if an environment is running in the us-east-1 region, defining the region value in the root directory allows any resource within the environment to inherit the value for its own use. This approach minimizes redundancy and ensures consistency throughout the environment. Terragrunt’s ability to define parameters at a higher level streamlines the configuration process and makes it easier to manage resources.

For instance, consider this use case:

Infra
   VPC
      Terragrunt.hcl
   Backend
      Service-01
         Terragrunt.hcl
      Service-02
         Terragrunt.hcl
   Terragrunt.hcl
Modules
   VPC
      Terragrunt.hcl
Terragrunt.hcl

Referring to the hierarchy, as shown above:

Infra: This concept organizes our environment and its structure by arranging the infrastructure in a specific order. This order starts with the VPC and everything related to it, followed by the backend and its various service definitions, and so on.
Modules: This concept connects us to a group of resources that we intend to utilize. For instance, if we have decided to use a VPC in our infrastructure, we would define its source artifactory and initialization parameters within the module scope. Similarly, if our backend includes a service like Kubernetes-dashboard, we would also define its source artifactory within the module scope, and so on.
Terragrunt.hcl: This file serves as the Terragrunt configuration file, as previously explained. However, we are also using it to define common values for the environment. For instance, if Service-01 and Service-02 share some common parameters, then we would define these parameters at a higher level in the Terragrunt.hcl file, under the backend scope, which is located in the root folder of both services.

Furthermore, we have created a Terragrunt.hcl file within the root directory. By doing so, we are consolidating common values that pertain to the all environment, and that other parts of the hierarchy do not need to be aware of. This approach allows us to propagate shared parameters downward in the hierarchy, enabling us to customize our environment without duplicating values.

Conclusion

Numerous organizations prioritize the aspect of quality as a fundamental objective that underpins the entire process. As such, it is crucial to ask the right questions in order to achieve this goal:

How do we envision the design of our cloud environment, taking into account both the production and development environments?
How can we model the environment in a way that minimizes the risk of errors in shared variables?
How flexible is the environment when it comes to accommodating rapid changes?

Based on our experience, we follow the following approach:

Begin by outlining the problem on paper.
Break down the problem into smaller, manageable modules.
Develop each module separately, using elastic thinking that enables the module to be reused in additional use cases, either by ourselves or other developers.
Abstract the implementation of the solution while avoiding code duplication, i.e., propagating shared variables for resources that have common values.

Sharing our acquired knowledge with the community is a priority for us, and we are excited to offer our solutions to anyone interested in learning from them. You can easily access and gain insights into our methods, and even implement them yourself.

As an additional resource, we have a Github repository that contains a multitude of examples for creating efficient and effective applications in a cloud environment using Terragrunt. You’re welcome to use this as a reference to help you develop your own solutions.