feat: Enable integration with multiple LBs

[jwadolowski]

what

Enable ECS service registration in multiple LB target groups (docs). Currently, only 1 ALB and 1 NLB can be associated with a given service definition.

why

There are scenarios where an ECS-hosted app needs to register itself into multiple target groups to handle use cases such as:

• traffic split between internal and internet-facing LBs
• handling of different protocols (e.g., HTTPS/gRPC) that require distinct target group configurations
• an app that exposes multiple ports (e.g. 80 + 8080 + 8443)
• etc

references

[coderabbitai]

📝 Walkthrough

Walkthrough

The changes introduce support for configuring additional load balancers. A new input parameter, additional_lbs, is documented and added to the configuration. This parameter accepts a list of objects with optional values for container_name and container_port (defaulting to the main container’s port) and a required target_group_arn. The implementation in the code creates a new local variable derived from this parameter and updates the aggregated load balancer list. Additionally, a corresponding variable is declared with the appropriate type and default value.

Changes

File(s)	Change Summary
docs/terraform.md	Added documentation for the new input parameter additional_lbs (list(object) with optional container_name and container_port, and required target_group_arn).
main.tf, variables.tf	In main.tf, introduced a new local variable additional_lbs using list comprehension and updated the load_balancers aggregation; in variables.tf, declared the new variable additional_lbs with its type, description, and default value ([]).

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Reviewing files that changed from the base of the PR and between 884d379 and f649a40.

⛔ Files ignored due to path filters (1)

• README.md is excluded by !README.md

📒 Files selected for processing (3)

• docs/terraform.md (1 hunks)
• main.tf (1 hunks)
• variables.tf (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (1)

• GitHub Check: Summary

🔇 Additional comments (4)

variables.tf (1)

1145-1153: Define New Variable for Additional Load Balancers

The new variable additional_lbs is defined with the correct type:

• Uses a list of objects with container_name and container_port marked as optional, and target_group_arn as required.
• The description clearly explains its purpose and the default value is set to an empty list.

This aligns with the PR objective to enable support for multiple load balancer target groups.

docs/terraform.md (1)

40-41: Document the New additional_lbs Input Parameter

The documentation section has been updated to include the new input parameter additional_lbs with a thorough description and correct type formatting. The documented type is consistent with that specified in variables.tf and clarifies that container_name and container_port are optional while target_group_arn is required.

main.tf (2)

129-136: Implement Local Block for Additional Load Balancers

The local variable additional_lbs is defined using a list comprehension that iterates over var.additional_lbs. The logic:

• Falls back to module.this.id if container_name is not provided.
• Falls back to var.container_port if container_port is null.
• Sets elb_name to null and correctly extracts target_group_arn.

This implementation is clean and meets the objective of configuring additional load balancer settings.

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138-142: Concatenate Updated Load Balancers List

The load_balancers local variable is now defined by concatenating:

• The primary ALB configuration [local.alb]
• A conditional inclusion of the NLB configuration (if defined)
• The new local.additional_lbs list

This ensures that additional load balancers are seamlessly integrated with the standard ALB and optionally an NLB configuration.

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[gberenice]

/terratest

[gberenice]

LGTM, thanks!

[github-actions]

These changes were released in v2.4.0.