Updating TopologyAwareHints feature gate to be on by default

[robscott]

What type of PR is this?

/kind bug
/kind cleanup

What this PR does / why we need it:

This was the intention with #106433 and matches the docs we currently have for Topology Aware Hints. The net effect of this is just allowing a separate Service annotation opt-in to actually be effective. This will have no effect on users that are not explicitly trying to use this feature.

Special notes for your reviewer:

Would like to cherry pick this to 1.23 if possible.

Does this PR introduce a user-facing change?

The `TopologyAwareHints` feature gate is now enabled by default. This will allow users to opt-in to Topology Aware Hints by setting the `service.kubernetes.io/topology-aware-hints` on a Service. This will not affect any Services without that annotation set. 

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

• Enhancement Issue: Topology Aware Routing enhancements#2433

/sig network
/priority important-soon
/cc @aojea @danwinship
/assign @thockin

[k8s-ci-robot]

@robscott: This issue is currently awaiting triage.

If a SIG or subproject determines this is a relevant issue, they will accept it by applying the triage/accepted label and provide further guidance.

The triage/accepted label can be added by org members by writing /triage accepted in a comment.

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/test-infra repository.

[aojea]

/lgtm

I defer to Tim for approval

Would like to cherry pick this to 1.23 if possible.

hmm, having a cluster in 1.23.4 that does not have a feature enabled by default and it does in 1.23.5 sounds a bit complex, in this case the the functionality does not seem a problem because of the annotation that you mention, but it runs additional code paths in the endpointslice controller (and IIRC we had a bug related to the nodename thing)

kubernetes/pkg/controller/endpointslice/endpointslice_controller.go

Lines 157 to 165 in e6c093d

	if utilfeature.DefaultFeatureGate.Enabled(features.TopologyAwareHints) {
	nodeInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
	AddFunc: c.addNode,
	UpdateFunc: c.updateNode,
	DeleteFunc: c.deleteNode,
	})
	c.topologyCache = topologycache.NewTopologyCache()
	}

What Jordan and Tim say?

cc @liggitt

[liggitt]

I'd also be surprised to see this feature change default enablement in a patch release... is there a concrete problem if default enablement happens in 1.24?

[robscott]

@aojea @liggitt That makes sense, I'm fine with leaving this to 1.24 only.

[thockin]

I can't support the cherry-pick either. :(

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: robscott, thockin

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

The pull request process is described here

Needs approval from an approver in each of these files:

• pkg/features/OWNERS [thockin]

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