feat: Add flag to limit the max number of targets added to an ELB #4361

mmiller-sh · 2025-09-28T00:39:39Z

Issue

Description

This change adds an optional flag to limit the maximum number of targets that are attempted to be added to a particular load balancer instance. The primary use-case is to prevent "Max targets" quotas from being hit and blocking the reconciliation loop.

The existing behavior is preserved by default (no limits).

Checklist

Added tests that cover your change (if possible)
Added/modified documentation as required (such as the README.md, or the docs directory)
Manually tested
Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

Backfilled missing tests for code in same general area 🎉
Refactored something and made the world a better place 🌟

linux-foundation-easycla · 2025-09-28T00:39:45Z

The committers listed above are authorized under a signed CLA.

✅ login: mmiller-sh / name: Matt Miller (9c74844, 79d47c0, 1becaac, ca9d382, 4cc76b0, 09030dd, 7a2218b)

k8s-ci-robot · 2025-09-28T00:39:48Z

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k8s-ci-robot · 2025-09-28T00:39:49Z

Hi @mmiller-sh. Thanks for your PR.

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zac-nixon · 2025-09-29T18:54:39Z

/ok-to-test

zac-nixon · 2025-09-29T20:06:02Z

pkg/targetgroupbinding/resource_manager.go

 			return "", "", false, ctrlerrors.NewErrorWithMetrics(controllerName, "update_tracked_ip_targets_error", err, m.metricsCollector)
 		}

+		eligibleTargetsCount := m.getMaxNewTargets(len(unmatchedEndpoints), len(targets), tgbScopedLogger)


instead of always doing the endpoint slicing, how about only doing it if m.maxTargetsPerInstance != 0

zac-nixon · 2025-09-29T20:09:38Z

docs/deploy/configurations.md

 | kube-ca-pem-filepath                                                               | string                          |                                            | The file path to the CA to validate webhook callers, when unspecified all webhook callers are permitted.                                                                      |
 | alb-gateway-max-concurrent-reconciles                                           | int                       | 3                                          | Maximum number of concurrently running reconcile loops for ALB gateways, if enabled                                                                                           |
 | nlb-gateway-max-concurrent-reconciles                                           | int                       | 3                                          | Maximum number of concurrently running reconcile loops for NLB gateways, if enabled                                                                                           |
+| max-targets-per-instance                                                        | int                       | 0                                          | Maximum number of targets that will be added to a given ELB instance. The default value of zero will leave the number of targets unlimited                                    |


name is a little confusing, per your issue link you ran into the max number of targets in a target group limitation. how about max-targets-per-target-group?

to expand, instance is pretty general, and it's not clear if you're referring to targets per load balancer, targets per target group, how many pods can get packed into a node, etc. There is also a separate limits:

https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-limits.html Targets per Application Load Balancer

https://docs.aws.amazon.com/elasticloadbalancing/latest/network/load-balancer-limits.html Targets per Network Load Balancer

In this case, it looks like you're enforcing the targets per target group quota.

Thanks @zac-nixon. I agree max-targets-per-target-group makes more sense for this. I've updated the PR to reflect this, as well as addressed your other comment regarding limiting when we perform the endpoint slice.

…ontroller

zac-nixon · 2025-10-03T13:35:00Z

/lgtm
/approved

thanks for the contribution!

k8s-ci-robot · 2025-10-03T17:09:17Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mmiller-sh, wweiwei-li

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k8s-ci-robot requested review from oliviassss and wweiwei-li September 28, 2025 00:39

k8s-ci-robot added the cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. label Sep 28, 2025

k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Sep 28, 2025

k8s-ci-robot added the size/M Denotes a PR that changes 30-99 lines, ignoring generated files. label Sep 28, 2025

mmiller-sh added 4 commits September 27, 2025 21:31

Initial testing

9c74844

working implementation on both target-type IP and NodePort

7a2218b

dedup max addition calculation

4cc76b0

update docs

79d47c0

mmiller-sh force-pushed the main branch from 7242056 to 79d47c0 Compare September 28, 2025 01:44

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. and removed cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Sep 28, 2025

some tidying

ca9d382

k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Sep 29, 2025

zac-nixon reviewed Sep 29, 2025

View reviewed changes

mmiller-sh added 2 commits September 29, 2025 21:12

Merge branch 'main' of github.com:kubernetes-sigs/aws-load-balancer-c…

09030dd

…ontroller

updates per review suggestions

1becaac

k8s-ci-robot assigned zac-nixon Oct 3, 2025

k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Oct 3, 2025

wweiwei-li approved these changes Oct 3, 2025

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k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Oct 3, 2025

k8s-ci-robot merged commit 650fb5a into kubernetes-sigs:main Oct 3, 2025
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zac-nixon mentioned this pull request Oct 17, 2025

🥳 aws-load-balancer-controller v2.14.1 Automated Release! 🥑 aws/eks-charts#1261

Merged

mmiller-sh mentioned this pull request Oct 22, 2025

feat: add maxTargetsPerTarget group flag to helm chart #4408

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feat: Add flag to limit the max number of targets added to an ELB #4361

feat: Add flag to limit the max number of targets added to an ELB #4361

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feat: Add flag to limit the max number of targets added to an ELB #4361

feat: Add flag to limit the max number of targets added to an ELB #4361

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mmiller-sh commented Sep 28, 2025

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