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

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

Wildcard configuration for a single hosting server

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 wildcard configuration for a single hosting server

$ 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

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