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Avinash Bendigeri Avinash is a developer-turned Technical writer skilled in core content creation. He has an excellent track record of blogging in areas like Docker, Kubernetes, IoT and AI.

Using Variables to Create Dynamic and Reusable Infrastructure Configurations

4 min read

Infrastructure-as-Code (IaC) has been steadily growing in popularity, with Terraform having emerged as one of the most widely-used IaC tools. This tool comes with a number of features and functions that make IaC management and resource provisioning significantly easier and more efficient.

Among the notable features of Terraform are “variables.” These serve as containers for values, which can range from simple text strings to more complex details. Variables enable the generation of dynamic infrastructure configurations that can be iterated for different environments. Also, they are vital in making configurations reusable in IaC.

More importantly, variables play an indirect role in making IaC configurations secure. Dynamic and reusable configurations do not only make it easy to deploy infrastructure and provision resources. They also factor in security to address attacks that target IaC code vulnerabilities.

Dynamic Configurations

Terraform variables are crucial in dynamic configurations, mainly because they enable the separation of the core infrastructure plan from the specific details of deployments in different environments. They are behind the abstraction of values across different environments. They also support context-aware configurations.

Variables are useful in abstracting values by serving as placeholders for values that are set to be modified depending on where they will be deployed. For example, the number of resources or resource types may be changed as the configuration is used in the development, staging, and production environments. Having variables allows organizations to set an infrastructure blueprint once and reuse it for multiple purposes. With the blueprint ready, they only need to change settings or values for specific deployments instead of doing everything repeatedly.

On the other hand, Terraform variables support the dynamic assignment of values, wherein values change according to the context of deployment. This context awareness allows a single blueprint to be easily repurposed for different region and availability zone deployments. For example, infrastructure can be deployed in different regions with variables for API endpoints, storage pricing, language codes, time zone settings, and content delivery network edge locations. 

In terms of availability zones, aside from the regional variables, organizations may also need variables for spread placement, latency factors, and disaster recovery planning to define regional specifications further.

Terraform has a command line interface (CLI), which is crucial in using dynamic configurations through variables. Here, Terraform output variables are processed to extract and display data from infrastructure configurations, particularly about the state of resources post-deployment. Terraform CLI and Terraform output play a central role in dynamic configurations because they are the tools for variable definition and input.

Dynamic configuration, in turn, is important for infrastructure security, because it has both beneficial and potentially damaging impact. It can be used to control attack surfaces by separating sensitive details from the Terraform code, implementing environment-specific security, automating security updates, and boosting configurability. However, it can also raise the complexity of configurations and the risks of misconfiguration, which can make infrastructure security more challenging.

Organizations need to master dynamic configurations with variables to maximize their benefits while reducing the risks. Efficiency should not be at the expense of security.

Reusable Configurations

Variables in Terraform are also a big part of making infrastructure configurations reusable. They enable the creation of reusable modules. They help reduce errors in specifying values. Additionally, variables ensure the consistency of configurations.

Reusable modules are a powerful feature in Terraform that ensure the systematic organization and reutilization of configurations across different environments. Meanwhile, variables are an important part of these modules, because they ( are an essential component of a module’s structure alongside and 

Common configurations such as network settings, machine type, number of instances, and security policies can be stored in variables, which are then easily applied to various deployments. Variables in modules allow the definition of common configurations, including security settings, while enabling customization when the configuration is already being used.

Since variables stand in for specific values within the Terraform configuration files, there is a lower likelihood of erroneously indicating values. The “define once, use everywhere” nature of variables significantly reduces the possibility of unnecessary duplication and mistakes in writing values. Instead of hardcoding values repeatedly, the values can be stored separately and referenced in the code. 

For instance, when specifying the same virtual private cloud (VPC) name, it is easier to create a variable like “vpc_name” then assign it the value “my-vpc” which is then referenced to a resource where the VPC name is required.

Moreover, variables are important in enforcing consistency in infrastructure configurations. There is a significant reduction of errors since values no longer have to be repeatedly hardcoded into the infrastructure. There are fewer opportunities to mistakenly enter the wrong values or have different values that are supposedly the same. 

Additionally, it is possible to enforce constraints for variables by defining data types that can be passed in. This is important when it comes to infrastructure security, as it ascertains that the variables are only assigned valid values. It ensures that the reusable configurations remain valid and free from errors and exploitable vulnerabilities brought about by the use of inappropriate values or incorrect data types.

Interweaving Roles

To recap, variables play vital roles in creating dynamic configurations and the reusability of these configurations. To achieve dynamic configurations, they serve as the abstractor of values and they are an important factor in making contextually aware deployments. When it comes to reusability, they are a key component of reusable modules. Their presence helps ensure configuration consistency and considerably reduces errors such as duplication and incorrect values.

Notably, these roles are interlaced. The ability of variables to abstract values is fundamental in having reusable configurations. The variables in modules leverage abstraction and contextual awareness to create configurations that can be iterated for different environments or projects without having to repeatedly hardcode all values. In a way, it creates centralized configuration (for some parts of the configuration) while also supporting environment-specific deployments. 

Both centralized configuration and environment specificity yield the benefits of dynamism, reduced errors, consistency, and reusability.

Understandably, these can be quite complex, especially for organizations that are still learning the ropes of IaC. It tends to relegate security to a lower priority, which should never be the case. Configurations should always be kept secure, especially in view of the growing attacks on cloud and hybrid infrastructures. In many cases, it’s necessary for organizations to employ security solutions or managed services that have the capabilities and expertise in dealing with IaC-related attacks and risks.

Making IaC Management More Efficient and Secure

Technically, it is possible to create and manage infrastructure configurations without Terraform variables. However, doing so would mean limited reusability since inputting values into configurations repetitiously is tedious and time-consuming. It is also highly prone to human error. Additionally, veering away from variables can lead to poor code readability and maintainability.

Terraform has some other features that can be used in lieu of variables like locals and command-line arguments. However, these have limited capabilities and do not approximate the efficiency and security advantages of variables. When taking on IaC management with Terraform, it is advisable to master the use of variables and take full advantage of their functions. 

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Avinash Bendigeri Avinash is a developer-turned Technical writer skilled in core content creation. He has an excellent track record of blogging in areas like Docker, Kubernetes, IoT and AI.
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