Скачать или смотреть How to Properly Use for_each in Terraform to Identify Target Group ARNs

This guide provides a clear explanation on how to resolve issues with identifying key elements using `for_each` in Terraform, specifically when working with AWS Load Balancers and target groups.
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This video is based on the question https://stackoverflow.com/q/68283234/ asked by the user 'Rostyslav Malenko' ( https://stackoverflow.com/u/2442879/ ) and on the answer https://stackoverflow.com/a/68283375/ provided by the user 'Marcin' ( https://stackoverflow.com/u/248823/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Terraform: Identifying Element Keys Using for_each

Introduction

When working with Terraform to set up AWS Network Load Balancers and their associated target groups, many users encounter challenges, particularly with identifying the correct elements using the for_each construct. This can result in error messages that can be confusing and may halt your deployment process. In this post, we'll dive into a common problem related to the aws_lb_listener resource and provide you with a clear and effective solution.

The Problem

Imagine you've defined two target groups for your AWS Load Balancer: one for HTTP traffic on port 80 and another for HTTPS on port 443. You also have various listeners set up for these ports using the aws_lb_listener resource. However, this is where many users run into problems.

An error message might read:

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

This indicates that while trying to reference the arn key dynamically in your listener resource, Terraform cannot find the specified key. Let's break down how to address this issue.

Understanding the Code Structure

Firstly, let's look at the variable definitions and how they would generally look:

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

Your listeners and target groups are created with the for_each construct, which means they need to be referenced correctly.

The Solution

When using dynamic blocks in Terraform, the key to correctly resolving references lies in using the appropriate identifiers. The solution to the error mentioned is to alter how the target_group_arn is referenced.

Correcting the Reference

Instead of accessing it with each.value.arn, which leads to the error, you should access the key in the context of the dynamic block. Here’s how you can resolve the issue:

Modify the Target Group ARN Reference:
Change your target_group_arn line within the dynamic block from:

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

to:

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

Defining a Single Default Action:
If you prefer to maintain a single default_action, you can utilize the following structure:

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

Final Thoughts

By correctly referencing your target group ARNs using the default_action identifier in conjunction with the key from your for_each, you can avoid common pitfalls associated with dynamic blocks in Terraform. This approach will not only streamline your configuration but also enhance your overall deployment workflow.

Feel free to test these changes in your Terraform scripts and ensure smooth integration of AWS Load Balancers and target groups in your infrastructure. Happy coding!