fix: Resource tags don't propagate to frontend NLB #4279

[praddy26]

Issue

Closes #4279

Description

This PR implements tag propagation from Application Load Balancer (ALB) to frontend Network Load Balancer (NLB) in the AWS Load Balancer Controller. The changes provide two ways to handle tags for frontend NLBs:

1. Frontend NLB-specific tags: Using the new annotation alb.ingress.kubernetes.io/frontend-nlb-tags to specify tags that should be applied only to the frontend NLB
2. ALB tag propagation: If no frontend-NLB specific tags are specified, the tags from ALB (specified via alb.ingress.kubernetes.io/tags) are automatically propagated to the frontend NLB

Key features implemented:

• New annotation support for frontend NLB-specific tags
• Automatic tag propagation from ALB when no specific NLB tags are provided
• Consistency checks to ensure matching tags across ingress group members
• Error handling for tag conflicts between group members

Implementation details:

• Added tag parsing and validation in the buildFrontendNlbTags function
• Implemented conflict detection for tags between ingress group members
• Maintains backward compatibility by falling back to ALB tags when no NLB-specific tags are provided

Example usage:

# Specifying NLB-specific tags
annotations:
  alb.ingress.kubernetes.io/frontend-nlb-tags: Environment=prod,Team=platform

# Using ALB tags that will propagate to NLB
annotations:
  alb.ingress.kubernetes.io/tags: Environment=prod,Team=platform

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: praddy26
Once this PR has been reviewed and has the lgtm label, please assign shraddhabang for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: praddy26 / name: Pradeep Lakshmi Narasimha (3b1f87b)

[k8s-ci-robot]

Welcome @praddy26!

It looks like this is your first PR to kubernetes-sigs/aws-load-balancer-controller 🎉. Please refer to our pull request process documentation to help your PR have a smooth ride to approval.

You will be prompted by a bot to use commands during the review process. Do not be afraid to follow the prompts! It is okay to experiment. Here is the bot commands documentation.

You can also check if kubernetes-sigs/aws-load-balancer-controller has its own contribution guidelines.

You may want to refer to our testing guide if you run into trouble with your tests not passing.

If you are having difficulty getting your pull request seen, please follow the recommended escalation practices. Also, for tips and tricks in the contribution process you may want to read the Kubernetes contributor cheat sheet. We want to make sure your contribution gets all the attention it needs!

Thank you, and welcome to Kubernetes. 😃

[k8s-ci-robot]

Hi @praddy26. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[praddy26]

/test

[k8s-ci-robot]

@praddy26: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.