feat(source): add gateway api hostname source annotation

[hjoshi123]

What does it do ?

Adds external-dns.alpha.kubernetes.io/gateway-hostname-source annotation to the GatewayAPI source.

Motivation

#5391

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

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[ivankatliarchuk]

/ok-to-test

[mloiseleur]

At first glance, it makes sense.
@abursavich Wdyt ? Anything I missed ? Do you think you can review this PR ?

[bdrewery]

I ran into a case of needing this too.
Probably should update docs/annotations/annotations.md or docs/sources/gateway-api.md or any doc.

[ivankatliarchuk]

Hi @bdrewery,

Would you be able to share an abstract with a use case for that annotation? This would be incredibly helpful for our documentation; it's always valuable to provide not just the feature itself, but also practical examples of how it can be used.

[ivankatliarchuk]

I think there is a great explanation about one of the use cases, we could re-use and add it to docs #5391 (comment)

Customers need to be able to resolve most of their traffic over the private endpoint, so they set up DNS for company.private.example.com to point to their internal VPC endpoint. The CNAME then directs traffic from company.public.example.com to company.private.example.com which resolves privately to their internal endpoint. This is then directed to our Gateway API private load balancer, then routed in-cluster.

Some limited traffic from third-party services that our customers use (namely SCIM) cannot traverse this private endpoint, so we need to have that traffic be able to resolve company.private.example.com to our public gateway instead. Inside their network, that will still resolve to their internal endpoint, but those third-party services will be able to send traffic to the public endpoint (which will only handle traffic for a \scim endpoint and blackhole everything else).

The problem is that the hostname those third-party services will have to use is company.public.example.com, so that's the hostname that we need to use on our HTTPRoute. We don't want to override our CNAME however, or that will break our customers other operations. We want external DNS to create ONLY an A record for company.private.example.com -> public gateway loadbalancer DNS, but the default behavior is to add both the hostname annotations and the hostname defined in the HTTPRoute spec, which causes it to override our ExernalName service's CNAME record with a message like this:

[hjoshi123]

@ivankatliarchuk yes I was gonna modify the documentation for ingress since the annotation's purpose is similar

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[hjoshi123]

@bdrewery @ivankatliarchuk added documentation.. let me know if the documentation works

[ivankatliarchuk]

/ok-to-test

[ivankatliarchuk]

In docs use-cases missing. And would you be able to share evidences that the code is working and make changes expected?

[hjoshi123]

Hmm.. @ivankatliarchuk I will try running it on my homelab over the weekend.. if someone can do it earlier then it would be better too.. the unit tests are passing though
also I think I did add the use-cases in docs/sources under why is this needed?

[mloiseleur]

/ok-to-test

[ivankatliarchuk]

Example use cases for another annotation https://github.com/kubernetes-sigs/external-dns/blob/master/docs/advanced/ttl.md#use-cases-for-external-dnsalphakubernetesiottl-annotation. This will help us and a community to decide which annotation to use

[hjoshi123]

Ah gotcha @ivankatliarchuk I can add it.. although I didn't get time to run this on a cluster.. but seems like the tests are passing.. I am not sure if any of you guys have bandwidth to try it out

[k8s-ci-robot]

PR needs rebase.

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[KalenWessel]

Checking in to see when this functionality will be merged in? I'm currently running into a similar scenario outlined in this comment

[ivankatliarchuk]

This PR abandoned. If anyone interested to add feature what is required;

• feat(source): add gateway api hostname source annotation #5487 (comment)
  So just run it against a cluster and confirm it's working.

Example result #5828 (comment)

If needed, see how to test a PR. This will require golang to be installed.

[bogdankrasko]

Smoke tests

Setup

args:
--kubeconfig=/Users/check/.kube/config \
--log-level=info \
--log-format=text \
--interval=1m \
--source=service \
--source=ingress \
--source=gateway-httproute \
--source=gateway-grpcroute \
--source=gateway-tlsroute \
--source=gateway-tcproute \
--source=gateway-udproute \
--policy=upsert-only \
--registry=txt \
--txt-owner-id=check-external.dns \
--provider=aws \
--zone-id-filter=/hostedzone/Z05480953F37UYZ***** \
--domain-filter=dev.poc.engineering

manifest:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: check-external-dns
  namespace: check
  annotations:
    external-dns.alpha.kubernetes.io/gateway-hostname-source: annotation-only
    external-dns.alpha.kubernetes.io/hostname:  >-
      api.us-east-2.check.dev.poc.engineering
spec:
  hostnames:
    - api.check.dev.poc.engineering
    - api.us-east-2.check.dev.poc.engineering
  parentRefs:
    - group: gateway.networking.k8s.io
      kind: Gateway
      name: public
      namespace: kube-system
  rules:
    - backendRefs:
        - group: ''
          kind: Service
          name: api-use2-1-dev-app
          port: 80

Master

INFO[0000] Instantiating new Kubernetes client          
INFO[0000] Using kubeConfig                             
INFO[0000] Created Kubernetes client https://28C0823905520B****.gr7.us-east-2.eks.amazonaws.com 
INFO[0003] Using kubeConfig                             
INFO[0003] Created GatewayAPI client https://28C0823905520B****.gr7.us-east-2.eks.amazonaws.com 
INFO[0007] Applying provider record filter for domains: [dev.poc.engineering. .dev.poc.engineering.] 
INFO[0007] All records are already up to date           
INFO[0066] Applying provider record filter for domains: [dev.poc.engineering. .dev.poc.engineering.] 
INFO[0067] Desired change: CREATE aaaa-api.us-east-2.check.dev.poc.engineering TXT  profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0067] Desired change: CREATE api.us-east-2.check.dev.poc.engineering A  profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0067] Desired change: CREATE api.us-east-2.check.dev.poc.engineering AAAA  profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0067] Desired change: CREATE api.us-east-2.check.dev.poc.engineering TXT  profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0067] Desired change: CREATE cname-api.us-east-2.check.dev.poc.engineering TXT  profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0067] 5 record(s) were successfully updated         profile=default zoneID=/hostedzone/Z05480953F37UYZ***** zoneName=dev.poc.engineering.
INFO[0127] Applying provider record filter for domains: [dev.poc.engineering. .dev.poc.engineering.] 
INFO[0127] All records are already up to date     

Notes

@ivankatliarchuk Tested feature with latest changes from master branch as well with fixed small merge conflict but I can't push a fix for merge conflict since I don't have persimmons.

# Merge conflict fix
# external-dns/source/annotations/annotations.go
// InternalHostnameKey The annotation used for defining the desired hostname
InternalHostnameKey = AnnotationKeyPrefix + "internal-hostname"
// The annotation used for defining the desired hostname source for gateways
GatewayHostnameSourceKey = AnnotationKeyPrefix + "gateway-hostname-source"

Should I create a new branch or you can fix it?

[mloiseleur]

Should I create a new branch or you can fix it?

@hjoshi123 Can you update your PR from @bogdankrasko branch ? Or should we create a new PR ?

[bogdankrasko]

@mloiseleur I've created a new pull request and tested changes #5959