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Expose an external application

Learn to expose a service located outside the Kubernetes cluster using an Ingress.

Before you begin ensure that you have Installed Kong Ingress Controller in your Kubernetes cluster and are able to connect to Kong.

Prerequisites

Install Kong

You can install Kong in your Kubernetes cluster using Helm.

Add the Kong Helm charts:

 helm repo add kong https://charts.konghq.com
 helm repo update

Install Kong Ingress Controller and Kong Gateway with Helm:

 helm install kong kong/ingress -n kong --create-namespace

Test connectivity to Kong

Kubernetes exposes the proxy through a Kubernetes service. Run the following commands to store the load balancer IP address in a variable named PROXY_IP:

Populate $PROXY_IP for future commands:

 HOST=$(kubectl get svc --namespace kong kong-gateway-proxy -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
 PORT=$(kubectl get svc --namespace kong kong-gateway-proxy -o jsonpath='{.spec.ports[0].port}')
 export PROXY_IP=${HOST}:${PORT}
 echo $PROXY_IP   

Ensure that you can call the proxy IP:

 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"}

If you are not able to connect to Kong, read the deployment guide.

Create a Kubernetes Service

Deploy a Kubernetes Service type=ExternalName using the hostname of the application you 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 -

The results should look like this:

 service/proxy-to-httpbin created

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

Ingress

Gateway APIs

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 -

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 -

The results should look like this:

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

Test the Service

curl -i -H 'Host:kong.example' $PROXY_IP/httpbin/anything

The results should look like this:

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"
}