Ingress (Kubernetes)

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.

1. Create an Istio Gateway:

   $ kubectl apply -f - <<EOF
   apiVersion: networking.k8s.io/v1beta1
   kind: Ingress
   metadata:
     annotations:
       kubernetes.io/ingress.class: istio
     name: ingress
   spec:
     rules:
     - host: httpbin.example.com
       http:
         paths:
         - path: /status/*
           backend:
             serviceName: httpbin
             servicePort: 8000
   EOF
   

   The kubernetes.io/ingress.class annotation is required to tell the Istio gateway controller that it should handle this Ingress, otherwise it will be ignored.

2. Access the httpbin service using curl:

   $ curl -I -HHost:httpbin.example.com http://$INGRESS_HOST:$INGRESS_PORT/status/200
   HTTP/1.1 200 OK
   server: envoy
   date: Mon, 29 Jan 2018 04:45:49 GMT
   content-type: text/html; charset=utf-8
   access-control-allow-origin: *
   access-control-allow-credentials: true
   content-length: 0
   x-envoy-upstream-service-time: 48
   

   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.

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

   $ curl -I -HHost:httpbin.example.com http://$INGRESS_HOST:$INGRESS_PORT/headers
   HTTP/1.1 404 Not Found
   date: Mon, 29 Jan 2018 04:45:49 GMT
   server: envoy
   content-length: 0
   

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.

Specifying IngressClass

In Kubernetes 1.18, a new resource, IngressClass, was added, replacing the kubernetes.io/ingress.class annotation on the Ingress resource. If you are using this resource, you will need to set the controller field to istio.io/ingress-controller. For example:

apiVersion: networking.k8s.io/v1beta1
kind: IngressClass
metadata:
  name: istio
spec:
  controller: istio.io/ingress-controller
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: ingress
spec:
  ingressClassName: istio
  ...

Cleanup

Delete the Ingress configuration, and shutdown the httpbin service:

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