Add all load balancing methods

[salonichf5]

Proposed changes

Write a clear and concise description that helps reviewers understand the purpose and impact of your changes. Use the
following format:

Problem: Users want to specify all load balancing methods.

Solution: Specify a way for user to be able to specify all combinations of load balancing methods.

Testing:

Manual testing

Errors

spec:
  targetRefs:
  - group: core
    kind: Service
    name: tea
  loadBalancingMethod: "hash"

The UpstreamSettingsPolicy "usp-lb" is invalid: spec: Invalid value: "object": hashKey is required when loadBalancingMethod is 'hash' or 'hash consistent'

hash key format wrong

  loadBalancingMethod: "hash"
  hashKey: "upstream"
The UpstreamSettingsPolicy "usp-lb" is invalid: spec.hashKey: Invalid value: "upstream": spec.hashKey in body should match '^\$[a-z_]+$'

plus features with OSS

  loadBalancingMethod: "least_time"
    Conditions:
      Last Transition Time:  2025-11-21T05:54:56Z
      Message:               spec.loadBalancingMethod: Invalid value: "least_time": NGINX OSS only supports the following load balancing methods: round_robin, least_conn, ip_hash, random, hash, hash consistent, random two, random two least_conn

Spec does not allow any other features so do not need to validate for plus(everything allowed)

The UpstreamSettingsPolicy "usp-lb" is invalid: 
* spec.loadBalancingMethod: Unsupported value: "invalid-method": supported values: "round_robin", "least_conn", "ip_hash", "hash", "hash consistent", "random", "random two", "random two least_conn", "random two least_time", "random two least_time=header", "random two least_time=last_byte", "least_time", "least_time header", "least_time last_byte", "least_time header inflight", "least_time last_byte inflight"
* <nil>: Invalid value: null: some validation rules were not checked because the object was invalid; correct the existing errors to complete validation

USP is set for tea svc for all , verified traffic passing for all

Only mentioning special cases -- round_robin, hash and hash consistent

OSS

• loadBalancingMethod: "round_robin"

upstream default_tea_80 {
    zone default_tea_80 1m;
    state /var/lib/nginx/state/default_tea_80.conf;

---

  loadBalancingMethod: "hash"
  hashKey: "$upstream_addr"

upstream default_tea_80 {
    hash $upstream_addr;
    zone default_tea_80 512k;


    server 10.244.0.27:8080;

---

  loadBalancingMethod: "hash consistent"
  hashKey: "$upstream_addr"

upstream default_tea_80 {
    hash $upstream_addr consistent;
    zone default_tea_80 512k;

Plus verified on tea svc

upstream default_tea_80 {
    least_time header;
    zone default_tea_80 1m;

    state /var/lib/nginx/state/default_tea_80.conf;

}

Verified all load balancing methods with working traffic for plus

Closes #4190

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

Release notes

If this PR introduces a change that affects users and needs to be mentioned in the release notes,
please add a brief note that summarizes the change.

NONE

[sjberman]

In your round_robin example in the description, it's using random two least_conn.

[sjberman]

And your hash example shows hash consistent.

[bjee19]

What's the reasoning behind inverting this function? Can we make the function return what we want without needing to invert it?

[salonichf5]

Yeah agree, feels counter intuitive. Just checks if anything of the load balancing fields conflicts, good catch.