fix(gateway-api): ensure to use only latest generation with HTTPRoutes

[kashalls]

Description

Adds a check to ensure that the parent of route is the current generation.
Fixes #5348

Checklist

• Unit tests updated
• End user documentation updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: kashalls / name: Jordan Jones (059daad, 219e19f, 11ca783, 0dcd6c9, e5f584f)
• ✅ login: tholinka / name: Tyler Holinka (1ad804c, 57ba990)

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[k8s-ci-robot]

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[ivankatliarchuk]

/ok-to-test

[kashalls]

/test pull-external-dns-unit-test

[kashalls]

/test pull-external-dns-unit-test

[ivankatliarchuk]

The code looks ok. Was it tested on real cluster setup? What was the result?

[tholinka]

I'm running it on my home cluster, I can confirm it results in only the newest generation having records generated, instead of all. I have an internal and an external gateway. Before if I switched a route from one to the other, I would run into #5348, now I only get the newest one when I flip it back and forth.

[tholinka]

Example logs of flipping it from external to internal:

Without this change:

time="2025-05-05T11:52:27-05:00" level=debug msg="Endpoints generated from HTTPRoute self-hosted/ocis: [files.domain.name 0 IN CNAME  external.domain.name;internal.domain.name []]"

With this change:

time="2025-05-05T11:53:48-05:00" level=debug msg="Endpoints generated from HTTPRoute self-hosted/ocis: [files.domain.name 0 IN CNAME  internal.domain.name []]"

[ivankatliarchuk]

/lgtm

cc @mloiseleur

[mloiseleur]

/retitle fix(gateway-api): ensure to use only latest generation with HTTPRoutes

@abursavich any comments on this PR ?

[mloiseleur]

/retitle fix(gateway-api): ensure to use only latest generation with HTTPRoutes

[kashalls]

Any updates on this? @mloiseleur @abursavich

[abursavich]

Sorry, I still haven't been able to review with as much attention as I would like. The goal of this change makes sense, but my first reaction is that it's actually very dangerous.

Erroneously rejecting a route could be worse than erroneously accepting a route update. After a route is updated (e.g. an annotation), its accepted generation will no longer match and ExternalDNS could delete the DNS records.

[kashalls]

Sorry, I still haven't been able to review with as much attention as I would like. The goal of this change makes sense, but my first reaction is that it's actually very dangerous.

Erroneously rejecting a route could be worse than erroneously accepting a route update. After a route is updated (e.g. an annotation), its accepted generation will no longer match and ExternalDNS could delete the DNS records.

That is a good point, the understanding is that External-DNS should only take action on the most up to date parentRefs. The chosen gateway controller is what handles that, but it doesn't specify that the gateway controller is supposed to clean up old instances that don't reflect the spec.

@tholinka and I can test this case where the annotations are modified real quick.

[kashalls]

I just verified that adding an annotation to the HTTPRoute without modifying the parentRefs still updates the route in external-dns. The generation number remained the same.

[abursavich]

ExternalDNS generates a list of all endpoints from cluster sources then syncs those with the external DNS provider. Unfortunately, it can't necessarily have access to a previous generation of an object's spec that matches the currently accepted generation. If we don't have matching generations when generating the endpoints, the sync could delete the DNS records.

The good news is that I believe the issue you're trying to fix was already fixed by #5241, which also checks the spec parentRefs instead of blindly trusting the status parentRefs.

[mloiseleur]

Thanks @kashalls 👍
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ivankatliarchuk, mloiseleur

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