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Configuring a fallback service

Learn to setup a fallback service using Ingress resource. The fallback service receives all requests that don’t match against any of the defined Ingress rules. This can be useful if you would like to return a 404 page to the end user if the user clicks a dead link or inputs an incorrect URL.

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.

1. Add the Kong Helm charts:

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

2. 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:

1. 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   
   

2. 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.

Setup a sample service

1. Deploy an example echo service.

    kubectl apply -f https://docs.konghq.com/assets/kubernetes-ingress-controller/examples/echo-service.yaml
   

   The results should look like this:

    deployment.apps/echo created
    service/echo created
   

2. Create an Ingress rule to proxy the echo service.

    $ echo '
    apiVersion: networking.k8s.io/v1
    kind: Ingress
    metadata:
      name: demo
      annotations:
        konghq.com/strip-path: "true"
    spec:
      ingressClassName: kong
      rules:
      - http:
          paths:
          - path: /echo
            pathType: ImplementationSpecific
            backend:
              service:
                name: echo
                port:
                  number: 1027
    ' | kubectl apply -f -
   

   The results should look like this:

    ingress.extensions/demo created
   

3. Test the Ingress rule:

    $ curl -i $PROXY_IP/echo
   

   The results should look like this:

    HTTP/1.1 200 OK
    Content-Type: text/plain; charset=utf-8
    Content-Length: 137
    Connection: keep-alive
    Date: Sun, 17 Sep 2023 19:45:02 GMT
    X-Kong-Upstream-Latency: 1
    X-Kong-Proxy-Latency: 0
    Via: kong/3.3.1
       
    Welcome, you are connected to node kind.
    Running on Pod echo-74d47cc5d9-9zbzh.
    In namespace default.
    With IP address 192.168.194.7.
   

Setup a fallback service

1. Deploy another sample service service.

   $ echo '
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: fallback-svc
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: fallback-svc
     template:
       metadata:
         labels:
           app: fallback-svc
       spec:
         containers:
         - name: fallback-svc
           image: hashicorp/http-echo
           args:
           - "-text"
           - "This is not the path you are looking for. - Fallback service"
           ports:
           - containerPort: 5678
   ---
   apiVersion: v1
   kind: Service
   metadata:
     name: fallback-svc
     labels:
       app: fallback-svc
   spec:
     type: ClusterIP
     ports:
     - port: 80
       targetPort: 5678
       protocol: TCP
       name: http
     selector:
       app: fallback-svc
   ' | kubectl apply -f -
   

   The results should look like this:

   deployment.apps/fallback-svc created
   service/fallback-svc created
   

2. Configure an Ingress rule to make it the fallback service to send all requests to it that don’t match any of the Ingress rules.

    $ echo "
    apiVersion: networking.k8s.io/v1
    kind: Ingress
    metadata:
      name: fallback
      annotations:
    spec:
      ingressClassName: kong
      defaultBackend:
        service:
          name: fallback-svc
          port:
            number: 80
    " | kubectl apply -f -
   

   The results should look like this:

    ingress.networking.k8s.io/fallback created
   

   Test the fallback service

   Send a request with a request property that doesn’t match any of the defined rules:

    $ curl $PROXY_IP/random-path
   

   The results should look like this:

    HTTP/1.1 200 OK
    Content-Type: text/plain; charset=utf-8
    Content-Length: 61
    Connection: keep-alive
    X-App-Name: http-echo
    X-App-Version: 0.2.3
    Date: Wed, 20 Sep 2023 09:46:56 GMT
    X-Kong-Upstream-Latency: 16
    X-Kong-Proxy-Latency: 0
    Via: kong/3.3.1
   
    This is not the path you are looking for. - Fallback service
   

   This message is from the fallback service that you deployed.

Create more Ingress rules, some complicated regex based ones and see how requests that don’t match any rules, are forwarded to the fallback service.

You can also use Kong’s request-termination plugin on the fallback Ingress resource to terminate all requests at Kong, without forwarding them inside the infrastructure.