Kubernetes Ingress

3 minute read page test

This task describes how to configure Istio to expose a service outside of the service mesh cluster, using the Kubernetes Ingress Resource.

Before you begin

Follow the instructions in the Before you begin and Determining the ingress IP and ports sections of the Ingress Gateways task.

Configuring ingress using an Ingress resource

A Kubernetes Ingress Resources exposes HTTP and HTTPS routes from outside the cluster to services within the cluster.

Let’s see how you can configure a Ingress on port 80 for HTTP traffic.

Create an Ingress resource and an IngressClass:

$ kubectl apply -f - <<EOF
apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  name: istio
spec:
  controller: istio.io/ingress-controller
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress
spec:
  ingressClassName: istio
  rules:
  - host: httpbin.example.com
    http:
      paths:
      - path: /status
        pathType: Prefix
        backend:
          service:
            name: httpbin
            port:
              number: 8000
EOF

The IngressClass resource identifies the Istio gateway controller to Kubernetes, and the ingressClassName: istio value instructs Kubernetes that the Istio gateway controller should handle the following Ingress.

Older versions of the Ingress API used the kubernetes.io/ingress.class annotation, and while it still works, it has been deprecated in Kubernetes for some time.

Access the httpbin service using curl:
```
$ curl -s -I -HHost:httpbin.example.com "http://$INGRESS_HOST:$INGRESS_PORT/status/200"
...
HTTP/1.1 200 OK
...
server: istio-envoy
...
```
Note that you use the -H flag to set the Host HTTP header to “httpbin.example.com”. This is needed because the Ingress is configured to handle “httpbin.example.com”, but in your test environment you have no DNS binding for that host and are simply sending your request to the ingress IP.

Access any other URL that has not been explicitly exposed. You should see an HTTP 404 error:

$ curl -s -I -HHost:httpbin.example.com "http://$INGRESS_HOST:$INGRESS_PORT/headers"
HTTP/1.1 404 Not Found
...

Next Steps

TLS

Ingress supports specifying TLS settings. This is supported by Istio, but the referenced Secret must exist in the namespace of the istio-ingressgateway deployment (typically istio-system). cert-manager can be used to generate these certificates.

Specifying path type

By default, Istio will treat paths as exact matches, unless they end in /* or .*, in which case they will become prefix matches. Other regular expressions are not supported.

In Kubernetes 1.18, a new field, pathType, was added. This allows explicitly declaring a path as Exact or Prefix.

Cleanup

Delete the IngressClass and Ingress configurations, and shutdown the httpbin service:

$ kubectl delete ingress ingress
$ kubectl delete ingressclass istio
$ kubectl delete --ignore-not-found=true -f @samples/httpbin/httpbin.yaml@