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Using External Service as Ingress Backend

You can use an external service as a Backend for Kubernetes Ingress. There are 2 options depending on whether the external service has an external IP or DNS record.

Using External IP

You can introduce any external IP address as a Kubernetes service by creating a matching Service and Endpoint object. Then you can use this service as a backend for your Ingress rules.

apiVersion: v1
kind: Service
metadata:
  name: external-ip
  namespace: default
spec:
  ports:
  - name: app
    port: 80
    protocol: TCP
    targetPort: 9855
  clusterIP: None
  type: ClusterIP
---
apiVersion: v1
kind: Endpoints
metadata:
  name: external-ip
  namespace: default
subsets:
- addresses:
  # list all external ips for this service
  - ip: 172.17.0.5
  ports:
  - name: app
    port: 9855
    protocol: TCP

Now, you can use this external-ip Service as a backend in your Ingress definition. For example:

apiVersion: voyager.appscode.com/v1
kind: Ingress
metadata:
  name: test-ings-rhvulnlb
  namespace: default
spec:
  defaultBackend:
    service:
      name: external-ip
      port:
        number: 80

Using External Domain

You can introduce an external service into a Kubernetes cluster by creating a ExternalName type service. Voyager can forward traffic in both HTTP and TCP mode to the named domain in the ExternalName service by resolving dns. For static resolution of DNS record when HAProxy config is parsed, only use the ingress.appscode.com/use-dns-resolver: "true" annotation on the respective service. To periodically resolve dns, DNS resolvers must be configured using annotations on the service name.

Following example illustrates the scenario.

apiVersion: v1
kind: Service
metadata:
  name: external-ns
  namespace: default
  annotations:
    ingress.appscode.com/use-dns-resolver: "true"
    ingress.appscode.com/dns-resolver-nameservers: '["8.8.8.8:53", "8.8.4.4:53"]'
spec:
  externalName: google.com
  type: ExternalName

If this service is used in ingress, the traffic will forward to google.com’s address.

apiVersion: voyager.appscode.com/v1
kind: Ingress
metadata:
  name: test-ings-rhvulnlb
  namespace: default
spec:
  defaultBackend:
    service:
      name: external-ns
      port:
        number: 80

HTTP Redirect

If ingress.appscode.com/use-dns-resolver annotation is set to false or missing on a ExternalName type service, Voyager resolves L7 ingress in the following ways.

apiVersion: v1
kind: Service
metadata:
  name: external-ns
  namespace: default
spec:
  externalName: google.com
  type: ExternalName

Default redirect

If No BackendRules are configured for the endpoint, Voyager will configure HAProxy to redirect traffic to provided domain and port. The redirect code will be 301 (permanent redirect). Scheme (http or https) used by endpoint is preserved on redirect.

backend:
  service:
    name: external-svc-non-dns
    port:
      number: 80

The generated redirect line in HAProxy config:

http-request redirect location http[s]://{{e.ExternalName}}:{{ e.Port }} code 301

Backend Rule

If Backendrules are configured, Voyager will not auto generate any redirect rule. This allows users to use full spectrum of HTTP redirection options available in HAProxy. To learn about these option, consult HAProxy documentation.

backend:
  backendRules:
  - http-request redirect location https://google.com code 302
  service:
    name: external-svc-non-dns
    port:
      number: 80