feat: Canary Deployments for AWS NLB

[ustndagsemih]

Summary

What change needs making?

Previously, AWS Network Load Balancers did not support weighted target groups, which prevented us from using NLBs for canary deployments.

With the latest update, NLBs now support assigning weights to target groups:
https://aws.amazon.com/about-aws/whats-new/2025/11/network-load-balancer-weighted-target-groups/

It would be great if Argo Rollouts could add support for this capability so that canary deployments can be performed using NLB weighted target groups.

Use Cases

When would you use this?

For our canary deployments.

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Message from the maintainers:

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[krapie]

Looks like AWS Load Balancer Controller already implemented features for NLB weighted target groups so that we can start implementing NLB canary rollout feature.

kubernetes-sigs/aws-load-balancer-controller#4455