How to Correctly Pass Variables into a Custom Terraform Module for AWS CodePipeline

Discover how to efficiently pass variables into your custom Terraform module for AWS CodePipeline, avoiding common pitfalls, and ensuring a seamless integration.
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How to Correctly Pass Variables into a Custom Terraform Module for AWS CodePipeline

Building a robust AWS CodePipeline using Terraform can be challenging, especially when it comes to passing variables correctly into your custom module. In this guide, we will explore a common problem faced when creating a dynamic pipeline configuration and how to resolve it effectively.

The Problem: Passing Variables into a Terraform Module

In the realms of Infrastructure as Code (IaC), Terraform allows for modular and reusable code structures. A common requirement is passing a variable map from a workspace file to a Terraform module. For those unaware, AWS CodePipeline is structured with stages that contain actions, often leading to complexity when trying to manage multiple stages and their associated actions.

The original issue arose when attempting to create a pipeline with two stages—each stage having its own configuration via a variable map. Unfortunately, the module encountered numerous errors due to incorrectly formatted YAML, leading to missing required arguments in the variables defined.

The Errors Encountered

The error messages indicated frequently missing required arguments, such as:

These messages suggest that the pipeline was not interpreting the variables as intended, leading to frustration and confusion in diagnosing the root cause.

The Solution: Correctly Formatting the YAML

Upon revisiting the YAML configuration, it became clear that the original YAML was malformed. Correcting the structure resolved the issue and enabled the module to read the values correctly. Here's a breakdown of the adjustments made to fix the issue.

Adjusted YAML Structure

Replace the original YAML structure with the following corrected version:

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Key Changes to Note

Field Names Consistency:

Ensure that the names used for the action fields (ActionName, ActionCategory, etc.) exactly match what your Terraform module expects. Consistency in naming is crucial.

YAML Formatting:

Check for proper indentation, brackets, and ensure that strings are correctly formatted. Issues in formatting can lead to Terraform not recognizing the data structure.

Remove Fallback Values:

As pointed out, providing null as a value fallback isn’t the best practice. Always ensure the necessary data is included in the configuration.

Conclusion

Passing variables into a custom Terraform module for AWS CodePipeline does not have to be fraught with errors. By ensuring your YAML is correctly structured and aligns with your module's expectations, you can create a seamless integration.

Next time you're tackling similar issues with your Terraform setup, remember to double-check your variable configurations and formatting. Happy coding, and may your pipelines run smoothly!