From Code Readability to Reusability, Here’s How Terraform Locals Enhance IaC Management

Terraform is among the leading tools used by enterprises as cloud computing continues to expand rapidly and Infrastructure-as-Code gains traction. The need for more effective and efficient IT solutions is becoming more pronounced as organizations grapple with the growing complexities of IT infrastructures and the enormity of cloud computing.

By now, those familiar with Terraform are already aware of its many benefits. However, it is also important to highlight one of the reasons why Terraform can deliver its advantages: Terraform locals. These are the named values that can be assigned and used in IaC configuration.

The concept of locals

Also known as local values or local variables, Terraform locals provide the means for expressing and storing values in the context of a specific code block. They are vital in defining values that are then referenced multiple times in different parts of the configuration. Terraform locals are used in data transformation like in formatting dates and other data sets, parsing strings, and generating dynamic values based on conditional logic. They are similarly used in mapping elements according to a set of criteria, conducting numerical operations, and structuring unstructured data.

Moreover, Terraform locals are used in the storage of static data needed in the configuration. They can be used to define constants and configuration parameters such as the instance types of virtual machines.

Terraform locals are one of the trifecta of Terraform variables employed to request values for configurations. The other two are the “input” and “output” variables. Locals are notably different from the other two because they are limited to the specific resource or module where they are defined.

It can be said that Terraform locals are responsible for most of the IaC management advantages that come with Terraform. They are a key element in achieving code readability, reusability, and a host of other important IaC management conveniences as explained below.

Code readability and ‘self-documentation’

Locals enable the assignment of custom names to values and expressions used in IaC configuration. They make it easier to identify these values and expressions or associate them with specific purposes. Human programmers can easily grasp what an expression is about without having to consult a reference. Also, code that uses locals tends to be “self-documenting” to some extent. Developers can more easily understand them as compared to code that makes use of expressions with unplanned semantics or random characters that rarely make sense.

Another readability benefit can be observed in how clean and organized the code is when using Terraform locals. This stems from the encapsulation of complex logic or calculations in locals instead of putting them up in the main configuration code.

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Easier maintenance

IaC code that uses locals is easier to maintain not only because of the inherent readability but also because of the centralized definitions. Locals support the centralized definition of expressions within a certain block, which means that it is significantly easier to update or modify values whenever necessary.

This centralization also means that changes to locals are automatically reflected regardless of where they are referenced. There is no need to manually inspect the code for consistency because all changes in locals are certain to be reflected as referenced. This entails a considerable reduction of configuration errors and inconsistencies in IaC.

Efficient version control

In connection with maintenance, locals also provide the benefit of efficient versioning, albeit indirectly. It facilitates the centralization of changes to shared values, which makes it easy to monitor the changes. Terraform locals do not come with a versioning system, but they help simplify the process for version control systems.

This version control advantage is important for infrastructure-as-code management not only for the benefit of the development team responsible for IaC configuration and management but also for collaborative efforts. This is convenient in allowing multiple teams to work together seamlessly.

Isolation

The limited scope of Terraform locals also comes with an advantage. As mentioned, locals are different from the input and output variables because their effects are constrained to a specific module or resource. This means that they can only be accessed within the resource where they are defined, making them isolated.

This isolation prevents conflicts when it comes to the names of variables and other locals that are defined in other parts of the codebase. This ensures that the unintentional overwriting of similarly named variables is avoided. Also, it precludes unintended interactions between different parts of the code, particularly the unwanted impact of locals on other parts of the IaC configuration.

Flexibility through dynamic configurations

Terraform locals enable flexible and adaptable IaC configurations by supporting the creation of dynamic values. They allow the definition and use of named expressions based on the values of other variables or local values that are dependent on certain conditions. This is an important feature that makes it possible for configurations to adapt to runtime conditions or specific requirements in a configuration.

Locals work with conditional logic that involves different environmental types and user inputs, mathematical calculations, and dynamic lists or maps. Also, locals are useful in the dynamic configuration of resource parameters and in string manipulation. They provide the flexibility that allows IaC configurations to respond to changes in environments, varying conditions, and user inputs.

Reusability

One of the most important benefits of Terraform locals is the reusability of the expressions and values. They provide an easy way to define and reuse expressions across a Terraform configuration. To be clear, though, locals do not make all of the IaC configuration reusable. It only contributes significantly to the reusability.

With locals, a central location for values and expressions is created. The configuration can then reference these expressions as many times as needed. There is no need to construct the same expressions and values repeatedly. When properly done, it ensures consistency and the reduction of errors brought about by variances in values.

Local scope, expansive benefits

Terraform locals may have a local scope, but the advantages they provide are wide-ranging. Not only do they empower code readability, but they also support code organization, maintainability, and reusability. All of which impact the overall efficiency of infrastructure-as-code configuration and management. Additionally, they help reduce errors by having a central location for shared values and expressions and a limited scope (isolation), which prevents the unwitting overwriting of expressions in different modules with similar names.