Скачать или смотреть How to Build a Map from Conditional Output Values in Terraform

Learn how to create a conditional map from output values in Terraform using the boolean `is_needed`. This guide breaks down the process step-by-step for a clearer understanding.
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How to Build a Map from Conditional Output Values in Terraform

When working with modules in Terraform, you may encounter a situation where certain outputs need to be conditionally included in a map based on a boolean value. This can be especially beneficial when managing configurations that require a combination of features or resources without cluttering your output with unnecessary data. In this post, we’ll discuss how to create a map from output values, conditionally excluding certain entries based on a boolean flag (is_needed in our case).

The Problem

Imagine you have a Terraform module that outputs a series of key-value pairs, along with a boolean indicator (is_needed) for whether each pair should be included in the final map. The challenge is to creatively construct this map such that only the pairs marked as is_needed are included.

Example Output Structure

Suppose your module's output looks like this:

[[See Video to Reveal this Text or Code Snippet]]

In this example, the first instance (instance_1) should not contribute to the final map since its is_needed value is false, while the second instance (instance_2) should be included because is_needed is true.

The Solution

Constructing the Conditional Map

To achieve this, we can leverage the powerful features of Terraform's tomap function alongside a conditional expression in a for-loop. Here’s how we can do it:

[[See Video to Reveal this Text or Code Snippet]]

This snippet effectively constructs a map from module.my_module, but only includes key-value pairs that have the is_needed flag set to true. Let's break down this code further.

Detailed Breakdown

For Loop: The for loop iterates over each instance in var.my_module.

Conditional Inclusion: Using the if instance.is_needed condition, the loop selectively adds only those key-value pairs that meet the requirement.

Mapping: Each selected instance contributes its key mapped to its value.

Example Code Block

Here's a complete Terraform code block that showcases this solution:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

The variable block defines our module's output, simulating what might be returned from an actual module.

The locals block contains our logic for filtering the outputs.

Finally, we have an output block that will display the map_of_needed_values, showing only those entries that were marked as needed.

Conclusion

Conditionally building a map from output values based on a boolean condition in Terraform can greatly enhance the manageability of your infrastructure code. By using a combination of loops and conditional expressions, you can streamline your outputs to keep your configurations clean and purposeful. Give it a try in your next Terraform project!