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docs(istio): document ingress annotation (#5756)
* docs(istio): document ingress annotation Signed-off-by: ivan katliarchuk <[email protected]> * docs(istio): document ingress annotation Co-authored-by: Michel Loiseleur <[email protected]> --------- Signed-off-by: ivan katliarchuk <[email protected]> Co-authored-by: Michel Loiseleur <[email protected]>
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‎docs/annotations/annotations.md‎

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@@ -4,25 +4,25 @@ ExternalDNS sources support a number of annotations on the Kubernetes resources
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The following table documents which sources support which annotations:
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| Source | controller | hostname | internal-hostname | target | ttl | (provider-specific) |
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|--------------|------------|----------|-------------------|---------|---------|---------------------|
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| Ambassador | | | | Yes | Yes | Yes |
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| Connector | | | | | | |
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| Contour | Yes | Yes[^1] | | Yes | Yes | Yes |
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| CloudFoundry | | | | | | |
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| CRD | | | | | | |
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| F5 | | | | Yes | Yes | |
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| Gateway | Yes | Yes[^1] | | Yes[^4] | Yes | Yes |
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| Gloo | | | | Yes | Yes[^5] | Yes[^5] |
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| Ingress | Yes | Yes[^1] | | Yes | Yes | Yes |
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| Istio | Yes | Yes[^1] | | Yes | Yes | Yes |
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| Kong | | Yes[^1] | | Yes | Yes | Yes |
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| Node | Yes | | | Yes | Yes | |
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| OpenShift | Yes | Yes[^1] | | Yes | Yes | Yes |
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| Pod | | Yes | Yes | Yes | | |
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| Service | Yes | Yes[^1] | Yes[^1][^2] | Yes[^3] | Yes | Yes |
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| Skipper | Yes | Yes[^1] | | Yes | Yes | Yes |
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| Traefik | | Yes[^1] | | Yes | Yes | Yes |
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| Source | controller | hostname | internal-hostname | target | ttl | (provider-specific) | ingress |
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|--------------|------------|----------|-------------------|---------|---------|---------------------|:-------:|
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| Ambassador | | | | Yes | Yes | Yes | No |
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| Connector | | | | | | | No |
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| Contour | Yes | Yes[^1] | | Yes | Yes | Yes | No |
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| CloudFoundry | | | | | | | No |
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| CRD | | | | | | | No |
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| F5 | | | | Yes | Yes | | No |
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| Gateway | Yes | Yes[^1] | | Yes[^4] | Yes | Yes | No |
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| Gloo | | | | Yes | Yes[^5] | Yes[^5] | No |
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| Ingress | Yes | Yes[^1] | | Yes | Yes | Yes | No |
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| Istio | Yes | Yes[^1] | | Yes | Yes | Yes | Yes |
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| Kong | | Yes[^1] | | Yes | Yes | Yes | No |
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| Node | Yes | | | Yes | Yes | | No |
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| OpenShift | Yes | Yes[^1] | | Yes | Yes | Yes | No |
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| Pod | | Yes | Yes | Yes | | | No |
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| Service | Yes | Yes[^1] | Yes[^1][^2] | Yes[^3] | Yes | Yes | No |
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| Skipper | Yes | Yes[^1] | | Yes | Yes | Yes | No |
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| Traefik | | Yes[^1] | | Yes | Yes | Yes | No |
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[^1]: Unless the `--ignore-hostname-annotation` flag is specified.
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[^2]: Only behaves differently than `hostname` for `Service`s of type `ClusterIP` or `LoadBalancer`.
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If the annotation is not present, use the domains from both the spec and annotations.
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## external-dns.alpha.kubernetes.io/ingress
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This annotation allows ExternalDNS to work with Istio Gateways that don't have a public IP.
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It can be used to address a specific architectural pattern, when a Kubernetes Ingress directs all public traffic to the Istio Gateway:
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- **The Challenge**: By default, ExternalDNS sources the public IP address for a DNS record from a Service of type LoadBalancer.
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However, in some service mesh setups, the Istio Gateway's Service is of type ClusterIP, with all public traffic routed to it via a separate Kubernetes Ingress object. This setup leaves the Gateway without a public IP that ExternalDNS can discover.
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- **The Solution**: The annotation on the Istio Gateway tells ExternalDNS to ignore the Gateway's Service IP. Instead, it directs ExternalDNS to a specified Ingress resource to find the target LoadBalancer IP address.
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## external-dns.alpha.kubernetes.io/internal-hostname
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Specifies the domain for the resource's DNS records that are for use from internal networks.

‎source/annotations/annotations.go‎

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SetIdentifierKey = AnnotationKeyPrefix + "set-identifier"
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AliasKey = AnnotationKeyPrefix + "alias"
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TargetKey = AnnotationKeyPrefix + "target"
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// The annotation used for figuring out which controller is responsible
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// ControllerKey The annotation used for figuring out which controller is responsible
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ControllerKey = AnnotationKeyPrefix + "controller"
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// The annotation used for defining the desired hostname
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// HostnameKey The annotation used for defining the desired hostname
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HostnameKey = AnnotationKeyPrefix + "hostname"
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// The annotation used for specifying whether the public or private interface address is used
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// AccessKey The annotation used for specifying whether the public or private interface address is used
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AccessKey = AnnotationKeyPrefix + "access"
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// The annotation used for specifying the type of endpoints to use for headless services
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// EndpointsTypeKey The annotation used for specifying the type of endpoints to use for headless services
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EndpointsTypeKey = AnnotationKeyPrefix + "endpoints-type"
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// The annotation used to determine the source of hostnames for ingresses. This is an optional field - all
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// Ingress the annotation used to determine if the gateway is implemented by an Ingress object
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Ingress = AnnotationKeyPrefix + "ingress"
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// IngressHostnameSourceKey The annotation used to determine the source of hostnames for ingresses. This is an optional field - all
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// available hostname sources are used if not specified.
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IngressHostnameSourceKey = AnnotationKeyPrefix + "ingress-hostname-source"
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// The value of the controller annotation so that we feel responsible
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// ControllerValue The value of the controller annotation so that we feel responsible
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ControllerValue = "dns-controller"
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// The annotation used for defining the desired hostname
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// InternalHostnameKey The annotation used for defining the desired hostname
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InternalHostnameKey = AnnotationKeyPrefix + "internal-hostname"
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)

‎source/istio_gateway.go‎

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// IstioGatewayIngressSource is the annotation used to determine if the gateway is implemented by an Ingress object
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// instead of a standard LoadBalancer service type
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const IstioGatewayIngressSource = "external-dns.alpha.kubernetes.io/ingress"
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const IstioGatewayIngressSource = annotations.Ingress
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// gatewaySource is an implementation of Source for Istio Gateway objects.
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// The gateway implementation uses the spec.servers.hosts values for the hostnames.

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