feat: added support per dns cf proxy

[Tazer]

Description

We have a use case where we want to have 1 domain proxied through cloudflare and another one not proxied via cloudflare but using the same service

So in this PR we are adding the possibility to pass a domain list in the external-dns.alpha.kubernetes.io/cloudflare-proxied

So it's still possible to pass
external-dns.alpha.kubernetes.io/cloudflare-proxied: true/false

but also
external-dns.alpha.kubernetes.io/cloudflare-proxied: example.com,bar.com

The setup we are going todo is like this:

external-dns.alpha.kubernetes.io/hostname: example.com,api.example.com
external-dns.alpha.kubernetes.io/cloudflare-proxied: example.com

Checklist

• Unit tests updated
• End user documentation updated

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The committers listed above are authorized under a signed CLA.

• ✅ login: Tazer / name: Patrik (a667d82, d139597, 82fa497, df5d200)

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[mloiseleur]

Thanks for this PR. The test looks good.
Would you please add:

1. some documentation on this
2. an other test with multiple cloudflare-proxied domains

I'm unsure to understand why you needed to make a deepcopy in endpoint.go, since this PR is not modifying any property.

Would you please detail what is the behavior you observed without the deepcopy ?

[mloiseleur]

/ok-to-test

[Tazer]

Thanks for this PR. The test looks good. Would you please add:

1. some documentation on this
2. an other test with multiple cloudflare-proxied domains

I'm unsure to understand why you needed to make a deepcopy in endpoint.go, since this PR is not modifying any property.

Would you please detail what is the behavior you observed without the deepcopy ?

First of all thanks for checking it out. @mloiseleur

will look at documentation and additional test tomorrow.

Let me explain the deepcopy need.

As we are using this functionality:

external-dns.alpha.kubernetes.io/hostname: example.com,api.example.com

on a kubernetes service.

The following code will run:

		providerSpecific, setIdentifier := getProviderSpecificAnnotations(svc.Annotations)
		var hostnameList []string
		var internalHostnameList []string

		hostnameList = getHostnamesFromAnnotations(svc.Annotations)
		for _, hostname := range hostnameList {
			endpoints = append(endpoints, sc.generateEndpoints(svc, hostname, providerSpecific, setIdentifier, false)...)
		}

so the tricky part here is that providerSpecific is a slice (underlying a pointer) and that is past to both endpoints in the list after the split by getHostnamesFromAnnotations(svc.Annotations)

source: https://github.com/kubernetes-sigs/external-dns/blob/master/source/service.go#L395

And in the cloudflare provider we have this code:

func (p *CloudFlareProvider) AdjustEndpoints(endpoints []*endpoint.Endpoint) ([]*endpoint.Endpoint, error) {
	adjustedEndpoints := []*endpoint.Endpoint{}
	for _, e := range endpoints {
		proxied := shouldBeProxied(e, p.proxiedByDefault)
		if proxied {
			e.RecordTTL = 0
		}
		e.SetProviderSpecificProperty(source.CloudflareProxiedKey, strconv.FormatBool(proxied))

		adjustedEndpoints = append(adjustedEndpoints, e)
	}
	return adjustedEndpoints, nil
}

And it will loop both of the endpoints. but on the first itirate it will call

e.SetProviderSpecificProperty(source.CloudflareProxiedKey, strconv.FormatBool(proxied))

Without DeepCopy, it will modify the slice referenced in both endpoints. This is basically setting external-dns.alpha.kubernetes.io/cloudflare-proxied: false (or true), meaning whatever gets evaluated first will set the proxied value to true or false and remove the external-dns.alpha.kubernetes.io/cloudflare-proxied: example.com

source: https://github.com/kubernetes-sigs/external-dns/blob/master/provider/cloudflare/cloudflare.go#L386

So the DeepCopy is needed, I guess the only thing is if it's the right place.I wanted to minimize code changes.

[Tazer]

@mloiseleur added docs & additional tests also explained the reasoning on DeepClone
#4325 (comment)

[mloiseleur]

Thanks @Tazer, it's clear.

You made quite a good job in order to avoid a breaking change 👍 .
I have to admit also I have doubts about this approach 🤔. First, it comes with impact : some users are handling thousands of records with external-dns and second, more important, should we really do that ?

I mean, sometimes, avoiding a breaking change may cause more harm than good.

In a fictional world where external-dns.alpha.kubernetes.io/hostname has only one entry (like in CloudFlare UI), setting proxied with a bool makes sense.

In the real world where external-dns.alpha.kubernetes.io/hostname may contains multiple entries, I don't see how this proxied annotations can be a bool.

Wdyt about:

1. Changing external-dns.alpha.kubernetes.io/proxied from a bool to a string
2. Format of this string could then be
   a. "true|all": proxy all hostnames
   b. "false|none": no proxy for all hostname
   c. "example.com,bar.com": proxy only for example.com and bar.com

cc @cxuu @aoz-turk @johngmyers @danie1sullivan as last PR authors on cloudflare
cc @szuecs @Raffo

[szuecs]

@mloiseleur I think we can change it from bool to string if this helps. For backwards compatibility we could try to cast as bool and if it's not ok we assume a string.

@Tazer wdyt?