Referencing variables in Nested Modules using Terraform

Description

Learn how to reference variables across nested modules in Terraform, enhancing your AWS Lambda authorizer setup. Follow our step-by-step guide to streamline your environment variable management. --- This video is based on the question https://stackoverflow.com/q/67608378/ asked by the user 'figuring' ( https://stackoverflow.com/u/15860635/ ) and on the answer https://stackoverflow.com/a/67608518/ provided by the user 'Mark B' ( https://stackoverflow.com/u/13070/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Referencing variables in nested modules in terraform Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Referencing variables in Nested Modules using Terraform: A Comprehensive Guide When working with Terraform to orchestrate multi-layered infrastructure, you may encounter the challenge of referencing variables between nested modules. This is especially relevant when you're developing an AWS Lambda authorizer for user pool authentication. In this guide, we will discuss how to dynamically set environment variables by navigating through nested module structures and referencing them properly. Understanding the Problem You have a directory structure like this: [[See Video to Reveal this Text or Code Snippet]] You want to grab the app_name from the application-service module and use it in your lambda-auth module for variable configuration. Here's where the challenge lies: you can't access variables directly across modules without properly declaring outputs and inputs. Files Involved Outputs: You’ve set up output values in outputs.tf to expose certain variables. Variables: You've declared various input variables in variables.tf for both application services and lambda auth. Solution Overview To reference variables across modules, you must follow these steps: Declare Outputs in the Parent Module: Export the necessary variables from the application-services module. Set Up Input Variables in the Target Module: Make sure that the lambda-auth module has variables to receive these values. Pass Variables in the Main Configuration: Finally, ensure that your main.tf file applies these values correctly. Step 1: Declare Outputs in application-services Expand your outputs.tf file located in src/modules/application-services/modules/application-service/outputs.tf as follows: [[See Video to Reveal this Text or Code Snippet]] Step 2: Input Variables in lambda-auth In the src/modules/lambda-auth/variables.tf, add the relevant input variable to accept app_name: [[See Video to Reveal this Text or Code Snippet]] Step 3: Pass Variables in main.tf Now, update your main.tf to pass these outputs properly to the lambda module: [[See Video to Reveal this Text or Code Snippet]] Complete File Structure Summary After implementing the changes, your final file structure should look like: src/modules/application-services/modules/application-service/outputs.tf src/modules/lambda-auth/variables.tf src/main.tf (with module adjustments) Why This Works Terraform Modules: Each module encapsulates its variables and outputs. By defining outputs, you expose values that can be consumed by other modules. Encapsulation: This design follows best practices by keeping modules self-contained yet interconnected. Conclusion Referencing variables in nested modules within Terraform can be daunting, but by carefully setting up outputs and inputs, you can successfully manage your AWS Lambda configurations. By leveraging this structured approach, you'll ensure efficient variable usage in your projects. With these steps, you’re well on your way to creating a robust Terraform configuration that caters to your AWS Lambda authorizer needs. Don’t hesitate to explore further optimizations as your infrastructure grows!