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27 Apr
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Simple Step-By-Step Tutorial on the Terraform Dynamic Block

Learn how to leverage Terraform dynamic block feature with this easy-to-follow tutorial. Enhance your infrastructure as code practices today.

Jack Dwyer

How To

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What is Terraform? Terraform is a powerful tool that simplifies the complexity of managing infrastructure in the cloud. In this intricate world, the ability to streamline and reuse configurations can make all the difference. One of the standout features of Terraform is dynamic blocks. These blocks allow you to generate nested block configurations within resources and data structures dynamically. They are particularly beneficial when structures require repeated nested blocks whose content and quantity might vary based on input variables or external data.

Dynamic blocks in Terraform consist of two essential components: the dynamic keyword followed by the nested block's name, and a content block that defines the structure of the dynamic block. Within this content block, iterator objects reference values to be assigned. For instance:

resource "provider_resource" "example" {
  argument = "value"
  # ... other arguments ...
  dynamic "argument_block_name" {
    for_each = var.collection # or expression
    content {
      # Block content

Dynamic Blocks in Terraform offer repeatable configuration blocks within a resource, provider, provisioner, or data source based on a variable, local, or expression used within them. Besides maintaining a Don't Repeat Yourself (DRY) configuration, Dynamic Blocks can help generate dynamic setups according to various inputs, allowing modules to cater to multiple use cases.

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Components of a Terraform Dynamic Block

boy using laptop in a office for Terraform dynamic block

Dynamic blocks are a powerful feature in Terraform that allow for the creation of nested blocks based on dynamic input. The components within a dynamic block are crucial to understand for effective usage. Let's break down the essential elements within a dynamic block:

Label: The Starting Point

The label within a dynamic block serves as the starting point. It specifies the type of nested block to generate. For instance, in the code snippet provided, the label is “subnet”. This tells Terraform to generate a subnet resource for each element in the variable var.subnets.

For_Each: Iterating Over the Complex Value

The for_each component is where the magic happens. It’s the complex value to iterate over. In the example, var.subnets holds the list of subnets to iterate through. This component is what enables dynamic block functionality, creating new instances based on the input data.

Iterator: Defining the Current Element

The iterator, although optional, is a handy component. It sets the name of a temporary variable that represents the current element. If not explicitly defined, it defaults to the label of the dynamic block. The iterator includes key and value attributes. The Key is the element index, while the Value is the element value being processed.

Content: The Block’s Body

The content component is where the specifics of each generated block reside. It’s within the content where the attributes of the nested block are defined. In the example, it would contain the configuration for the subnet resource being created

Multi-Level Nested Blocks: Clarifying with Iterators

Working with multi-level nested blocks brings complexity. Clearly defining iterators for each block is recommended to avoid ambiguities. By using the iterator component, each level in the configuration can be clearly marked. This helps in distinguishing attributes and nested blocks with similar names.

Nested Block Example: A Clear Illustration

The code example provided in the document illustrates a nested block scenario. The iterators are explicitly defined for each block, enhancing clarity in the configuration. In this nested block example, both outer_block and inner_block iterators are used to differentiate between the levels of nesting.

By understanding these components within a dynamic block, you can harness Terraform’s full potential. Whether it’s generating multiple instances of a resource or handling complex nested block structures, dynamic blocks offer a flexible and powerful way to manage your infrastructure.

Why Implement a Terraform Dynamic Block?

2 boys smiling while using laptop for Terraform dynamic block

Dynamic blocks in Terraform provide several advantages that significantly enhance the efficiency and scalability of infrastructure deployment. By simplifying the code and making it more concise, dynamic blocks offer speed and agility in writing and processing the code, resulting in quicker infrastructure deployment. This efficiency enables DevOps teams to make necessary changes swiftly and maintain a rapid development pace.

Enhanced Code Efficiency

The clear and readable structure of dynamic blocks enhances the overall code efficiency and reduces the likelihood of errors. By eliminating repetitive code blocks and condensing them into dynamic constructs, the code becomes easier to read, understand, and maintain. This clarity not only accelerates the development process but also reduces the chances of errors due to the simplicity and straightforwardness of the code.

​​Streamlining Code Reusability

Dynamic blocks facilitate the reusability of code segments through variables and parameters, enabling developers to streamline the replication and modification of code. Copying and pasting large code blocks can be cumbersome and error-prone, but dynamic blocks, when combined with variables, simplify this process and promote code reuse. This reusability reduces redundancy in the codebase and promotes consistency in code implementation, enhancing the overall reliability of the infrastructure deployment process.

​​Efficient Resource Deployment

In specific scenarios where repetitive resource deployments are required, dynamic blocks excel by offering a more efficient and scalable approach to defining infrastructure resources. By leveraging dynamic constructs like `for_each` and `count`, administrators can easily deploy similar resources without the need to declare individual code blocks. This feature provides a flexible and powerful capability that simplifies the management of resources and enhances the agility of infrastructure deployment.

Rapid and Scalable Infrastructure Deployments

For highly dynamic and complex infrastructure setups, the use of dynamic blocks in Terraform projects is instrumental in achieving rapid, error-free, and scalable deployments. By leveraging the speed, clarity, reusability, and reliability benefits of dynamic blocks, DevOps teams can optimize their infrastructure deployment processes and streamline their development workflows.

Optimizing Cloud Deployments

Using dynamic blocks in Terraform can help you achieve seamless cloud deployments that can transform your engineering team into strong individual contributors. Zeet can help you get more from your cloud, Kubernetes, and Terraform investments by providing a robust CI/CD and deployment platform. 

Contact Zeet to learn more about how we can help you get seamless cloud deployments every time and transform your team into a top-performing engineering unit.

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Application of Dynamic Blocks in Various Terraform Constructs

office colleagues working on computer exploring Terraform dynamic block

The use of dynamic blocks in Terraform offers a more flexible approach when defining resources. Instead of explicitly writing out each subnet block, a dynamic block allows for cleaner, more maintainable code.

In the example provided, a virtual network resource in Azure is configured with four subnets. The initial configuration explicitly lists each subnet block. 

Subnet Configuration with Dynamic Blocks

By utilizing a dynamic block and a variable to define the subnet configuration, the code becomes more concise and easier to manage. The dynamic block iterates over the values in the subnets variable, creating a subnet block for each item found.

Enhancing Code Reusability

By using dynamic blocks, the need for repeated attributes is eliminated, promoting better code reuse and reducing the chances of errors. The iterator within the dynamic block can be used to access the values from the variable, allowing for dynamic naming and attribute assignment.

Advanced Techniques and Tips for Terraform Dynamic Blocks

2 person sitting and using laptop on a table exploring Terraform dynamic block

Dynamic blocks are not limited to resource blocks in Terraform. They can also be used within data blocks. In the given example, dynamic blocks in data blocks are shown. Here, the code fetches EC2 instance details based on specific requirements specified in the data block. The dynamic block helps dynamically generate nested filter blocks, keeping the code clean and easy to read.

Resource Management with Dynamic Blocks in Terraform

The dynamic blocks within data blocks allow for a more structured and efficient way of managing resources in Terraform. Instead of repeating individual filter blocks based on varied requirements, dynamic blocks offer an organized approach. 

The use of dynamic blocks within data blocks enhances the scalability and readability of the Terraform code, making it easier to maintain and update as needed. The dynamic nature of these blocks ensures flexibility in managing complex configurations while adhering to the DRY (Don’t Repeat Yourself) principle of software development.

Best Practices for Utilizing Terraform Dynamic Blocks

team head explaining Terraform dynamic block to his team

When it comes to using dynamic blocks in Terraform, I like to keep things simple and straightforward. Overusing dynamic blocks can make it harder to understand your code in the future, and that's a headache I'd rather avoid. Make sure you're only using dynamic blocks in places where they're truly necessary and can save you time and effort.

Name Your Iterators With Purpose

Another thing I always keep in mind when working with dynamic blocks is to give my iterators meaningful names. It might be tempting to keep things simple and reuse the block name, but using a descriptive name for your iterator can make your code much easier to understand later on.

Validate Your Data

Dynamic Blocks rely on data to be generated. If you're using a variable, make sure you take advantage of the validation block to set up different conditions. If you're working with a local, be sure to run data checks through loops and functions to keep everything running smoothly.

Scalability Considerations

As you start creating multiple instances of resources or configurations with Dynamic Blocks, keep scalability concerns in mind. Provisioning a ton of resources in a cloud environment can take a toll on performance and cost. You might even run into service limits if you're not careful.

Consistent Documentation

Thoroughly document your Terraform code—especially your nested dynamic blocks—to make things as easy as possible for your team to understand. Trust me, you'll save yourself and your colleagues a lot of time and headaches down the line by keeping your code well-documented and easy to follow.

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Zeet helps you to get more from your cloud, Kubernetes, and Terraform investments and helps your engineering team become strong individual contributors through our CI/CD & deployment platform. 

Contact Zeet to learn more about how Zeet help you get seamless cloud deployments every time, and helps your team to become a top-performing engineering team.

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