Egress using Wildcard Hosts

The Accessing External Services task and the Configure an Egress Gateway example describe how to configure egress traffic for specific hostnames, like edition.cnn.com. This example shows how to enable egress traffic for a set of hosts in a common domain, for example *.wikipedia.org, instead of configuring each and every host separately.

Background

Suppose you want to enable egress traffic in Istio for the wikipedia.org sites in all languages. Each version of wikipedia.org in a particular language has its own hostname, e.g., en.wikipedia.org and de.wikipedia.org in the English and the German languages, respectively. You want to enable egress traffic by common configuration items for all the Wikipedia sites, without the need to specify every language’s site separately.

Before you begin

  • Install Istio using the demo configuration profile and with the blocking-by-default outbound traffic policy:

    $ istioctl install --set profile=demo --set meshConfig.outboundTrafficPolicy.mode=REGISTRY_ONLY
    
  • Deploy the sleep sample app to use as a test source for sending requests. If you have automatic sidecar injection enabled, run the following command to deploy the sample app:

    Zip
    $ kubectl apply -f @samples/sleep/sleep.yaml@
    

    Otherwise, manually inject the sidecar before deploying the sleep application with the following command:

    Zip
    $ kubectl apply -f <(istioctl kube-inject -f @samples/sleep/sleep.yaml@)
    
  • Set the SOURCE_POD environment variable to the name of your source pod:

    $ export SOURCE_POD=$(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name})
    

Configure direct traffic to a wildcard host

The first, and simplest, way to access a set of hosts within a common domain is by configuring a simple ServiceEntry with a wildcard host and calling the services directly from the sidecar. When calling services directly (i.e., not via an egress gateway), the configuration for a wildcard host is no different than that of any other (e.g., fully qualified) host, only much more convenient when there are many hosts within the common domain.

  1. Define a ServiceEntry for *.wikipedia.org:

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: ServiceEntry
    metadata:
      name: wikipedia
    spec:
      hosts:
      - "*.wikipedia.org"
      ports:
      - number: 443
        name: https
        protocol: HTTPS
    EOF
    
  2. Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:

    $ kubectl exec "$SOURCE_POD" -c sleep -- sh -c 'curl -s https://en.wikipedia.org/wiki/Main_Page | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
    <title>Wikipedia, the free encyclopedia</title>
    <title>Wikipedia – Die freie Enzyklopädie</title>
    

Cleanup direct traffic to a wildcard host

$ kubectl delete serviceentry wikipedia

Configure egress gateway traffic to a wildcard host

When all wildcard hosts are served by a single server, the configuration for egress gateway-based access to a wildcard host is very similar to that of any host, with one exception: the configured route destination will not be the same as the configured host, i.e., the wildcard. It will instead be configured with the host of the single server for the set of domains.

  1. Create an egress Gateway for *.wikipedia.org, a destination rule and a virtual service to direct the traffic through the egress gateway and from the egress gateway to the external service.

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: Gateway
    metadata:
      name: istio-egressgateway
    spec:
      selector:
        istio: egressgateway
      servers:
      - port:
          number: 443
          name: https
          protocol: HTTPS
        hosts:
        - "*.wikipedia.org"
        tls:
          mode: PASSTHROUGH
    ---
    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: egressgateway-for-wikipedia
    spec:
      host: istio-egressgateway.istio-system.svc.cluster.local
      subsets:
        - name: wikipedia
    ---
    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: direct-wikipedia-through-egress-gateway
    spec:
      hosts:
      - "*.wikipedia.org"
      gateways:
      - mesh
      - istio-egressgateway
      tls:
      - match:
        - gateways:
          - mesh
          port: 443
          sniHosts:
          - "*.wikipedia.org"
        route:
        - destination:
            host: istio-egressgateway.istio-system.svc.cluster.local
            subset: wikipedia
            port:
              number: 443
          weight: 100
      - match:
        - gateways:
          - istio-egressgateway
          port: 443
          sniHosts:
          - "*.wikipedia.org"
        route:
        - destination:
            host: www.wikipedia.org
            port:
              number: 443
          weight: 100
    EOF
    
  2. Create a ServiceEntry for the destination server, www.wikipedia.org.

    $ kubectl apply -f - <<EOF
    apiVersion: networking.istio.io/v1alpha3
    kind: ServiceEntry
    metadata:
      name: www-wikipedia
    spec:
      hosts:
      - www.wikipedia.org
      ports:
      - number: 443
        name: https
        protocol: HTTPS
      resolution: DNS
    EOF
    
  3. Send HTTPS requests to https://en.wikipedia.org and https://de.wikipedia.org:

    $ kubectl exec "$SOURCE_POD" -c sleep -- sh -c 'curl -s https://en.wikipedia.org/wiki/Main_Page | grep -o "<title>.*</title>"; curl -s https://de.wikipedia.org/wiki/Wikipedia:Hauptseite | grep -o "<title>.*</title>"'
    <title>Wikipedia, the free encyclopedia</title>
    <title>Wikipedia – Die freie Enzyklopädie</title>
    
  4. Check the statistics of the egress gateway’s proxy for the counter that corresponds to your requests to *.wikipedia.org. If Istio is deployed in the istio-system namespace, the command to print the counter is:

    $ kubectl exec "$(kubectl get pod -l istio=egressgateway -n istio-system -o jsonpath='{.items[0].metadata.name}')" -c istio-proxy -n istio-system -- pilot-agent request GET clusters | grep '^outbound|443||www.wikipedia.org.*cx_total:'
    outbound|443||www.wikipedia.org::208.80.154.224:443::cx_total::2
    

Cleanup egress gateway traffic to a wildcard host

$ kubectl delete serviceentry www-wikipedia
$ kubectl delete gateway istio-egressgateway
$ kubectl delete virtualservice direct-wikipedia-through-egress-gateway
$ kubectl delete destinationrule egressgateway-for-wikipedia

Cleanup

  • Shutdown the sleep service:

    Zip
    $ kubectl delete -f @samples/sleep/sleep.yaml@
    
  • Uninstall Istio from your cluster:

    $ istioctl uninstall --purge -y
    
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