# Using ExternalDNS with kube-ingress-aws-controller This tutorial describes how to use ExternalDNS with the [kube-ingress-aws-controller][1]. [1]: https://github.com/zalando-incubator/kube-ingress-aws-controller ## Setting up ExternalDNS and kube-ingress-aws-controller Follow the [AWS tutorial](aws.md) to setup ExternalDNS for use in Kubernetes clusters running in AWS. Specify the `source=ingress` argument so that ExternalDNS will look for hostnames in Ingress objects. In addition, you may wish to limit which Ingress objects are used as an ExternalDNS source via the `ingress-class` argument, but this is not required. For help setting up the Kubernetes Ingress AWS Controller, that can create ALBs and NLBs, follow the [Setup Guide][2]. [2]: https://github.com/zalando-incubator/kube-ingress-aws-controller/tree/HEAD/deploy ### Optional RouteGroup [RouteGroup][3] is a CRD, that enables you to do complex routing with [Skipper][4]. First, you have to apply the RouteGroup CRD to your cluster: ``` kubectl apply -f https://github.com/zalando/skipper/blob/HEAD/dataclients/kubernetes/deploy/apply/routegroups_crd.yaml ``` You have to grant all controllers: [Skipper][4], [kube-ingress-aws-controller][1] and external-dns to read the routegroup resource and kube-ingress-aws-controller to update the status field of a routegroup. This depends on your RBAC policies, in case you use RBAC, you can use this for all 3 controllers: ```yaml apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: kube-ingress-aws-controller rules: - apiGroups: - extensions - networking.k8s.io resources: - ingresses verbs: - get - list - watch - apiGroups: - extensions - networking.k8s.io resources: - ingresses/status verbs: - patch - update - apiGroups: - zalando.org resources: - routegroups verbs: - get - list - watch - apiGroups: - zalando.org resources: - routegroups/status verbs: - patch - update ``` See also current RBAC yaml files: - [kube-ingress-aws-controller](https://github.com/zalando-incubator/kubernetes-on-aws/blob/dev/cluster/manifests/ingress-controller/01-rbac.yaml) - [skipper](https://github.com/zalando-incubator/kubernetes-on-aws/blob/dev/cluster/manifests/skipper/rbac.yaml) - [external-dns](https://github.com/zalando-incubator/kubernetes-on-aws/blob/dev/cluster/manifests/external-dns/01-rbac.yaml) [3]: https://opensource.zalando.com/skipper/kubernetes/routegroups/#routegroups [4]: https://opensource.zalando.com/skipper ## Deploy an example application Create the following sample "echoserver" application to demonstrate how ExternalDNS works with ingress objects, that were created by [kube-ingress-aws-controller][1]. ```yaml apiVersion: apps/v1 kind: Deployment metadata: name: echoserver spec: replicas: 1 selector: matchLabels: app: echoserver template: metadata: labels: app: echoserver spec: containers: - image: gcr.io/google_containers/echoserver:1.4 imagePullPolicy: Always name: echoserver ports: - containerPort: 8080 --- apiVersion: v1 kind: Service metadata: name: echoserver spec: ports: - port: 80 targetPort: 8080 protocol: TCP type: ClusterIP selector: app: echoserver ``` Note that the Service object is of type `ClusterIP`, because we will target [Skipper][4] and do the HTTP routing in Skipper. We don't need a Service of type `LoadBalancer` here, since we will be using a shared skipper-ingress for all Ingress. Skipper use `hostNetwork` to be able to get traffic from AWS LoadBalancers EC2 network. ALBs or NLBs, will be created based on need and will be shared across all ingress as default. ## Ingress examples Create the following Ingress to expose the echoserver application to the Internet. ```yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: annotations: kubernetes.io/ingress.class: skipper name: echoserver spec: rules: - host: echoserver.mycluster.example.org http: &echoserver_root paths: - backend: serviceName: echoserver servicePort: 80 path: / - host: echoserver.example.org http: *echoserver_root ``` The above should result in the creation of an (ipv4) ALB in AWS which will forward traffic to skipper which will forward to the echoserver application. If the `--source=ingress` argument is specified, then ExternalDNS will create DNS records based on the hosts specified in ingress objects. The above example would result in two alias records being created, `echoserver.mycluster.example.org` and `echoserver.example.org`, which both alias the ALB that is associated with the Ingress object. Note that the above example makes use of the YAML anchor feature to avoid having to repeat the http section for multiple hosts that use the exact same paths. If this Ingress object will only be fronting one backend Service, we might instead create the following: ```yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: annotations: external-dns.alpha.kubernetes.io/hostname: echoserver.mycluster.example.org, echoserver.example.org kubernetes.io/ingress.class: skipper name: echoserver spec: rules: - http: paths: - backend: serviceName: echoserver servicePort: 80 path: / ``` In the above example we create a default path that works for any hostname, and make use of the `external-dns.alpha.kubernetes.io/hostname` annotation to create multiple aliases for the resulting ALB. ## Dualstack ALBs AWS [supports](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/application-load-balancers.html#ip-address-type) both IPv4 and "dualstack" (both IPv4 and IPv6) interfaces for ALBs. The Kubernetes Ingress AWS controller supports the `alb.ingress.kubernetes.io/ip-address-type` annotation (which defaults to `ipv4`) to determine this. If this annotation is set to `dualstack` then ExternalDNS will create two alias records (one A record and one AAAA record) for each hostname associated with the Ingress object. Example: ```yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: annotations: alb.ingress.kubernetes.io/ip-address-type: dualstack kubernetes.io/ingress.class: skipper name: echoserver spec: rules: - host: echoserver.example.org http: paths: - backend: serviceName: echoserver servicePort: 80 path: / ``` The above Ingress object will result in the creation of an ALB with a dualstack interface. ExternalDNS will create both an A `echoserver.example.org` record and an AAAA record of the same name, that each are aliases for the same ALB. ## NLBs AWS has [NLBs](https://docs.aws.amazon.com/elasticloadbalancing/latest/network/introduction.html) and [kube-ingress-aws-controller][1] is able to create NLBs instead of ALBs. The Kubernetes Ingress AWS controller supports the `zalando.org/aws-load-balancer-type` annotation (which defaults to `alb`) to determine this. If this annotation is set to `nlb` then ExternalDNS will create an NLB instead of an ALB. Example: ```yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: annotations: zalando.org/aws-load-balancer-type: nlb kubernetes.io/ingress.class: skipper name: echoserver spec: rules: - host: echoserver.example.org http: paths: - backend: serviceName: echoserver servicePort: 80 path: / ``` The above Ingress object will result in the creation of an NLB. A successful create, you can observe in the ingress `status` field, that is written by [kube-ingress-aws-controller][1]: ```yaml status: loadBalancer: ingress: - hostname: kube-ing-lb-atedkrlml7iu-1681027139.$region.elb.amazonaws.com ``` ExternalDNS will create a A-records `echoserver.example.org`, that use AWS ALIAS record to automatically maintain IP addresses of the NLB. ## RouteGroup (optional) [Kube-ingress-aws-controller][1], [Skipper][4] and external-dns support [RouteGroups][3]. External-dns needs to be started with `--source=skipper-routegroup` parameter in order to work on RouteGroup objects. Here we can not show [all RouteGroup capabilities](https://opensource.zalando.com/skipper/kubernetes/routegroups/), but we show one simple example with an application and a custom https redirect. ```yaml apiVersion: zalando.org/v1 kind: RouteGroup metadata: name: my-route-group spec: backends: - name: my-backend type: service serviceName: my-service servicePort: 80 - name: redirectShunt type: shunt defaultBackends: - backendName: my-service routes: - pathSubtree: / - pathSubtree: / predicates: - Header("X-Forwarded-Proto", "http") filters: - redirectTo(302, "https:") backends: - redirectShunt ```