Expose an external application

This example shows how we can expose a service located outside the Kubernetes cluster using an Ingress.

Installation

Follow the deployment documentation to install the Kong Ingress Controller on the Kubernetes cluster.

Installing the Gateway APIs

If you wish to use the Gateway APIs examples, follow the supplemental Gateway APIs installation instructions.

Testing connectivity to Kong Gateway

Ensure that the PROXY_IP environment variable is set to contain the IP address or URL pointing to Kong Gateway. The deployment guide that you used to install the Kong Ingress Controller on the Kubernetes cluster provides the instructions to configure this environment variable.

If everything is set correctly, a request to Kong Gateway returns a HTTP 404 Not Found status code:

curl -i $PROXY_IP

The results should look like this:

HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Content-Length: 48
X-Kong-Response-Latency: 0
Server: kong/3.0.0

{"message":"no Route matched with those values"}

This is expected because Kong Gateway doesn’t know how to proxy the request yet.

Create a configuration group

Ingress and Gateway APIs controllers need a configuration that indicates which set of routing configuration they should recognize. This allows multiple controllers to coexist in the same cluster. Before creating individual routes, you need to create a class configuration to associate routes with:

echo "
apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  name: kong
spec:
  controller: ingress-controllers.konghq.com/kong
" | kubectl apply -f -

ingressclass.networking.k8s.io/kong configured

echo "
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: GatewayClass
metadata:
  name: kong
  annotations:
    konghq.com/gatewayclass-unmanaged: 'true'

spec:
  controllerName: konghq.com/kic-gateway-controller
---
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: kong
spec:
  gatewayClassName: kong
  listeners:
  - name: proxy
    port: 80
    protocol: HTTP
" | kubectl apply -f -

gatewayclass.gateway.networking.k8s.io/kong created
gateway.gateway.networking.k8s.io/kong created

kubectl get gateway kong

NAME   CLASS   ADDRESS        READY   AGE
kong   kong    203.0.113.42   True    4m46s

Kong Ingress Controller recognizes the kong IngressClass and konghq.com/kic-gateway-controller GatewayClass by default. Setting the CONTROLLER_INGRESS_CLASS or CONTROLLER_GATEWAY_API_CONTROLLER_NAME environment variable to another value overrides these defaults.

Create a Kubernetes Service

First we need to create a Kubernetes Service type=ExternalName using the hostname of the application we want to expose:

echo "
kind: Service
apiVersion: v1
metadata:
  name: proxy-to-httpbin
spec:
  ports:
  - protocol: TCP
    port: 80
  type: ExternalName
  externalName: httpbin.org
" | kubectl apply -f -

Response:

service/echo created

Create an Ingress to expose the service at the path /httpbin

echo "
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: proxy-from-k8s-to-httpbin
  annotations:
    konghq.com/strip-path: 'true'
spec:
  ingressClassName: kong
  rules:
  - host: kong.example
    http:
      paths:
      - path: /httpbin
        pathType: ImplementationSpecific
        backend:
          service:
            name: proxy-to-httpbin
            port:
              number: 80
" | kubectl apply -f -

ingress.networking.k8s.io/proxy-from-k8s-to-httpbin created

echo "
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: proxy-from-k8s-to-httpbin
  annotations:
    konghq.com/strip-path: 'true'
spec:
  parentRefs:
  - name: kong
  hostnames:
  - 'kong.example'
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /httpbin
    backendRefs:
    - name: proxy-to-httpbin
      kind: Service
      port: 80
" | kubectl apply -f -

httproute.gateway.networking.k8s.io/proxy-from-k8s-to-httpbin created

Test the Service

curl -si http://kong.example/httpbin/anything --resolve kong.example:80:$PROXY_IP

Response:

HTTP/1.1 200 OK
Date: Thu, 15 Dec 2022 21:31:47 GMT
Content-Type: application/json
Content-Length: 341
Connection: keep-alive
Server: gunicorn/19.9.0
Access-Control-Allow-Origin: *
Access-Control-Allow-Credentials: true
X-Kong-Upstream-Latency: 2
X-Kong-Proxy-Latency: 1
Via: kong/3.1.1

{
  "args": {},
  "data": "",
  "files": {},
  "form": {},
  "headers": {
    "Accept": "*/*",
    "Host": "httpbin.org",
    "User-Agent": "curl/7.86.0",
    "X-Amzn-Trace-Id": "Root=1-639b9243-7cdb670008b8189a5948d619"
  },
  "json": null,
  "method": "GET",
  "origin": "136.25.153.9",
  "url": "http://httpbin.org/anything"
}