Infrastructure-as-Code (IaC) has significantly improved the way organizations build and manage their cloud-based IT infrastructure. IaC allows organizations to put all provisioning, management, and maintenance settings into code for easier and faster deployment. This code can then be tweaked and reused for other deployments, making the process considerably more efficient. Additionally, IaC facilitates consistent security policy enforcement, as security is taken care of in the code itself rather than being dependent on separate and disjointed configurations.
While IaC is known for setting configurations that can be repeated in different environments, it also emphasizes the importance of local values. These values are essentially configuration settings that are specific to an environment. They might change according to where the IaC scripts are executed, and they can be customized to suit specific requirements in an environment.
While recognizing the broad impact of IaC management, it can be helpful to consider the local aspects of IaC practices. Indeed, local values play a vital part in IaC provisioning and management, which is why organizations need to thoroughly understand and maximize their use.
Terraform Locals
Local values in Infrastructure-as-code are foundational constructs used for creating dynamic programs, especially when it comes to storing temporary values for programming logic. One example of local values is Terraform’s use of local values, also known simply as “locals.” These are among the three variants of Terraform variables, along with inputs and outputs. Designated by the “locals” block, local variables are a set of key-value pairs in IaC configuration that can be hard-coded or referenced multiple times to undertake data transformation.
Proper use of Terraform locals is a crucial part of IaC management. It is not only a requirement for correct deployment, as its purpose goes beyond convenience. The way you use locals also impacts security, environment specificity, version control, resource optimization, and collaboration.
Locals are different from input variables in that they are defined by an internal expression, not at runtime. Also, local values can be assigned any valid Terraform expression, whereas input variable values cannot originate from other configuration sources, and their default values cannot be overruled. On the other hand, locals are unlike output variables in that they are confined to the module, whereas output variables generally have broader scopes.
Securing Secrets
Sensitive information like API keys and account login credentials should never be directly indicated in the IaC codebase. Doing otherwise would make it easy for threat actors to obtain secrets, passwords, and other information they can use to compromise supposedly secure systems.
Local variables make it possible to store sensitive information in environment-specific locations such as password vaults and configuration management tools with encryption or other security functions. This is one way of improving the management of secrets while reducing attack surfaces.
When using Terraform for IaC management, secrets can be stored in credential management tools like the AWS Secrets Manager and HashiCorp Vault. Also, secrets can be referenced with Terraform secrets through Terraform interpolation with the ${var.name} syntax and backend-specific methods, such as the use of Terraform Cloud.
If your team uses Terraform Cloud, then you already have access to functionality that allows you to manage local values securely.
Configurations for Different Environments
Resource needs and infrastructure configurations can greatly vary across different environments. They can have significant deviations in areas like production, staging, and development.
Local values provide a simple and straightforward solution to address these differences. They enable the definition of configurations that are specific to certain environments without requiring an overhaul or revisions of the core IaC code. Doing this speeds up deployments while also guaranteeing the consistency of IaC practices in the process of adapting to the needs at different stages.
Terraform locals support environment specificity by providing the ability to define local values after identifying the configuration elements that vary across environments. Examples of local values that can be defined for environment-specific configuration include resource names and conditional configuration.
Resource Optimization
In the process of provisioning and managing resources with IaC, it is inevitable to encounter cases where the allocation of storage sizes, memory, and other resource configurations vary from one environment to another. This can be quite cumbersome, but local values help resolve the differences. Through local values, the IaC code can be decluttered and made cleaner and easier to maintain.
In the case of Terraform, resource optimization happens by coordinating resource requirements to environments with the help of instance types, resource counts, and storage requirement definitions. Organizations can define locals that match environment names to corresponding instance types to automatically provision the right instance type according to the environment.
With resource counts, locals can guide the determination of the amount of resources required for a specific environment on a dynamic basis. Moreover, locals help optimize the allocation of storage by providing the ability to define local values for storage size according to varying environment requirements.
Code Reusability and Scalability
It is also worth noting that local values play a role in enabling code reusability. The IaC code can have core infrastructure configurations tailored for different regions or environments based on local values and variables.
This makes it considerably easier and faster to deploy infrastructure because the IaC code does not have to be rewritten or revised heavily whenever it has to be reused or applied to broader deployments.
Terraform provides all these advantages as it enables the creation of generic templates with environmental flexibility. Local values support the production of generic IaC templates that can be readily adapted for different environments. It eliminates the need for several virtually identical scripts for different environments.
Enabling Collaboration
Aside from the advantages discussed above, the use of local values is also a boon for collaboration. Local values empower teams to produce generic IaC templates that outline core infrastructure configuration for specific services or applications. These templates act as a single source of truth for core IaC logic and help prevent the possibility of configuration drifts.
Additionally, local values support environment-specific customization, as they enable individual developers to define specific configurations in specific files. This, in turn, allows teams to customize configurations for specific environments without the need to change the core IaC template, which lowers the risks of accidental and unwanted changes and enhances maintainability.
Moreover, the use of local values is advantageous in terms of version control. With local values stored in separate files, it is easier to manage versions for different environments alongside the IaC code. This is not strictly necessary, but it helps to maintain environment-specific configurations, especially for debugging purposes and to understand the evolution of configurations.
The Need for Moderation
Local values are highly useful in IaC provisioning and management. They are helpful for avoiding the repetition of the same expressions or values in the core IaC code.
However, it is possible for locals to be overused. In particular, the excessive use of local values can make it difficult to read configurations. Teams that take over the maintenance of IaC code may have a hard time understanding the configuration because almost all of the actual values are hidden.
That’s why it is advisable to employ local values in moderation. They are applicable in situations where a single value or result is used in many areas of a given configuration. However, in relatively simple deployments and cases of limited collaboration, it might be better to avoid them.
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