APIs from External URLs

External Services refer to remote APIs that are located outside a Kubernetes cluster.

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Introduction

Traefik Hub uses the ExternalName Service of Kubernetes to manage APIs which are running outside the Kubernetes cluster, such as VMs or other systems.

Using an External Domain Name

ExternalName Services don't have selectors, or any defined ports or endpoints, therefore, you can use an ExternalName Service to direct traffic to an external Service.

Using an external domain name service tells the system that the DNS name in the externalName field (api.apis.guru) is the location of the resource that backs the service.

When a DNS request is made against the Kubernetes DNS server, it returns the externalName in a CNAME record, informing the client to look up the returned name to get the IP address.

ExternalName Services are implemented at the DNS level. A CNAME DNS record is created for the service. Therefore, clients connecting to the service will connect to the external service directly.

Managing external URLs Using CRDs

Field	Description	Required
spec.type	The Kubernetes Service type, for example, ExternalName.	Yes
spec.type.externalName	Specifies the location (FQDN) at which that external Service can be reached at, for example, api.apis.guru.	Yes
spec.type.ports.port	Specifies the reachable port of the external Service.	No

Examples

ExternalName object

Defines ExternalName object

apiVersion: v1
kind: Service
metadata:
  name: api-apis-guru
  namespace: traefik
spec:
  type: ExternalName
  # FQDN of the external API
  externalName: api.apis.guru
  ports:
    - port: 443

Complete example

A fully working example with all needed CRDs

apiVersion: hub.traefik.io/v1alpha1
kind: APIAccess
metadata:
  name: api-apis-guru
  namespace: traefik
spec:
  groups:
    - support
  apiSelector:
    matchLabels:
      app: api-apis-guru

---
apiVersion: hub.traefik.io/v1alpha1
kind: APIGateway
metadata:
  name: api-apis-guru
  namespace: traefik
spec:
  apiAccesses:
    - api-apis-guru

---
apiVersion: hub.traefik.io/v1alpha1
kind: APIPortal
metadata:
  name: api-apis-guru
  namespace: traefik
spec:
  title: "External Service api.apis.guru example"
  description: "This shows an example about how to use Traefik Hub with an external API."
  apiGateway: api-apis-guru

---
apiVersion: v1
kind: Service
metadata:
  name: api-apis-guru
  namespace: traefik
spec:
  type: ExternalName
  externalName: api.apis.guru
  ports:
    - port: 443

---
apiVersion: hub.traefik.io/v1alpha1
kind: API
metadata:
  name: api-apis-guru
  namespace: traefik
  labels:
    app: api-apis-guru
spec:
  pathPrefix: /demo
  service:
    name: api-apis-guru
    port:
      number: 443
    openApiSpec:
      url: https://raw.githubusercontent.com/APIs-guru/openapi-directory/main/APIs/apis.guru/2.2.0/openapi.yaml