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istio.io/content/docs/tasks/traffic-management/egress/index.md

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title description weight aliases keywords
Control Egress Traffic Describes how to configure Istio to route traffic from services in the mesh to external services. 40
/docs/tasks/egress.html
traffic-management
egress

By default, Istio-enabled services are unable to access URLs outside of the cluster because the pod uses iptables to transparently redirect all outbound traffic to the sidecar proxy, which only handles intra-cluster destinations.

This task describes how to configure Istio to expose external services to Istio-enabled clients. You'll learn how to enable access to external services by defining ServiceEntry configurations, or alternatively, to bypass the Istio proxy for a specific range of IPs.

Before you begin

  • Setup Istio by following the instructions in the Installation guide.

  • Start the [sleep]({{< github_tree >}}/samples/sleep) sample which you use as a test source for external calls.

    If you have enabled automatic sidecar injection, deploy the sleep application:

    {{< text bash >}} $ kubectl apply -f @samples/sleep/sleep.yaml@ {{< /text >}}

    Otherwise, you have to manually inject the sidecar before deploying the sleep application:

    {{< text bash >}} $ kubectl apply -f <(istioctl kube-inject -f @samples/sleep/sleep.yaml@) {{< /text >}}

    Note that any pod that you can exec and curl from will do for the procedures below.

  • Set the SOURCE_POD environment variable to the deployed sleep pod:

    {{< text bash >}} export SOURCE_POD=(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) {{< /text >}}

Configuring Istio external services

Using Istio ServiceEntry configurations, you can access any publicly accessible service from within your Istio cluster. This task shows you how to access an external HTTP service, httpbin.org, as well as an external HTTPS service, www.google.com.

Configuring an external HTTP service

  1. Create a ServiceEntry to allow access to an external HTTP service:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: httpbin-ext spec: hosts:

    • httpbin.org ports:
    • number: 80 name: http protocol: HTTP resolution: DNS location: MESH_EXTERNAL EOF {{< /text >}}

  2. Exec into the sleep service source pod:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh {{< /text >}}

  3. Make a request to the external HTTP service:

    {{< text bash >}} $ curl http://httpbin.org/headers {{< /text >}}

Configuring an external HTTPS service

  1. Create a ServiceEntry to allow access to an external HTTPS service. For TLS protocols, including HTTPS, a VirtualService is required in addition to the ServiceEntry. Without it, exactly what service or services are exposed by the ServiceEntry is undefined. The VirtualService must include a tls rule with sni_hosts in the match clause to enable SNI routing.

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: ServiceEntry metadata: name: google spec: hosts:

    • www.google.com ports:
    • number: 443 name: https protocol: HTTPS resolution: DNS location: MESH_EXTERNAL

    apiVersion: networking.istio.io/v1alpha3 kind: VirtualService metadata: name: google spec: hosts:

    • www.google.com tls:
    • match:
      • port: 443 sni_hosts:
        • www.google.com route:
      • destination: host: www.google.com port: number: 443 weight: 100 EOF {{< /text >}}

  2. Exec into the sleep service source pod:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh {{< /text >}}

  3. Make a request to the external HTTPS service:

    {{< text bash >}} $ curl https://www.google.com {{< /text >}}

Setting route rules on an external service

Similar to inter-cluster requests, Istio routing rules can also be set for external services that are accessed using ServiceEntry configurations. In this example, you set a timeout rule on calls to the httpbin.org service.

  1. From inside the pod being used as the test source, make a curl request to the /delay endpoint of the httpbin.org external service:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh $ time curl -o /dev/null -s -w "%{http_code}\n" http://httpbin.org/delay/5 200

    real 0m5.024s user 0m0.003s sys 0m0.003s {{< /text >}}

    The request should return 200 (OK) in approximately 5 seconds.

  2. Exit the source pod and use kubectl to set a 3s timeout on calls to the httpbin.org external service:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: networking.istio.io/v1alpha3 kind: VirtualService metadata: name: httpbin-ext spec: hosts: - httpbin.org http:

    • timeout: 3s route:
      • destination: host: httpbin.org weight: 100 EOF {{< /text >}}

  3. Wait a few seconds, then make the curl request again:

    {{< text bash >}} $ kubectl exec -it $SOURCE_POD -c sleep sh $ time curl -o /dev/null -s -w "%{http_code}\n" http://httpbin.org/delay/5 504

    real 0m3.149s user 0m0.004s sys 0m0.004s {{< /text >}}

    This time a 504 (Gateway Timeout) appears after 3 seconds. Although httpbin.org was waiting 5 seconds, Istio cut off the request at 3 seconds.

Calling external services directly

If you want to completely bypass Istio for a specific IP range, you can configure the Envoy sidecars to prevent them from intercepting the external requests. This can be done by setting the global.proxy.includeIPRanges variable of Helm and updating the ConfigMap istio-sidecar-injector by using kubectl apply. After istio-sidecar-injector is updated, the value of global.proxy.includeIPRanges will affect all the future deployments of the application pods.

The simplest way to use the global.proxy.includeIPRanges variable is to pass it the IP range(s) used for internal cluster services, thereby excluding external IPs from being redirected to the sidecar proxy. The values used for internal IP range(s), however, depends on where your cluster is running. For example, with Minikube the range is 10.0.0.1/24, so you would update your ConfigMap istio-sidecar-injector like this:

{{< text bash >}} $ helm template install/kubernetes/helm/istio --set global.proxy.includeIPRanges="10.0.0.1/24" -x templates/sidecar-injector-configmap.yaml | kubectl apply -f - {{< /text >}}

Note that you should use the same Helm command you used to install Istio, in particular, the same value of the --namespace flag. In addition to the flags you used to install Istio, add --set global.proxy.includeIPRanges="10.0.0.1/24" -x templates/sidecar-injector-configmap.yaml.

Redeploy the sleep application as described in the Before you begin section.

Set the value of global.proxy.includeIPRanges

Set the value of global.proxy.includeIPRanges according to your cluster provider.

IBM Cloud Private

  1. Get your service_cluster_ip_range from IBM Cloud Private configuration file under cluster/config.yaml:

    {{< text bash >}} $ cat cluster/config.yaml | grep service_cluster_ip_range {{< /text >}}

    The following is a sample output:

    {{< text plain >}} service_cluster_ip_range: 10.0.0.1/24 {{< /text >}}

  2. Use --set global.proxy.includeIPRanges="10.0.0.1/24"

IBM Cloud Kubernetes Service

Use --set global.proxy.includeIPRanges="172.30.0.0/16\,172.20.0.0/16\,10.10.10.0/24"

Google Container Engine (GKE)

The ranges are not fixed, so you will need to run the gcloud container clusters describe command to determine the ranges to use. For example:

{{< text bash >}} $ gcloud container clusters describe XXXXXXX --zone=XXXXXX | grep -e clusterIpv4Cidr -e servicesIpv4Cidr clusterIpv4Cidr: 10.4.0.0/14 servicesIpv4Cidr: 10.7.240.0/20 {{< /text >}}

Use --set global.proxy.includeIPRanges="10.4.0.0/14\,10.7.240.0/20"

Azure Container Service(ACS)

Use --set global.proxy.includeIPRanges="10.244.0.0/16\,10.240.0.0/16

Minikube

Use --set global.proxy.includeIPRanges="10.0.0.1/24"

Docker For Desktop

Use --set global.proxy.includeIPRanges="10.96.0.0/12"

Bare Metal

Use the value of your service-cluster-ip-range. It's not fixed, but the default value is 10.96.0.0/12. To determine your actual value:

{{< text bash >}} $ kubectl describe pod kube-apiserver -n kube-system | grep 'service-cluster-ip-range' --service-cluster-ip-range=10.96.0.0/12 {{< /text >}}

Access the external services

After updating the ConfigMap istio-sidecar-injector and redeploying the sleep application, the Istio sidecar will only intercept and manage internal requests within the cluster. Any external request bypasses the sidecar and goes straight to its intended destination. For example:

{{< text bash >}} export SOURCE_POD=(kubectl get pod -l app=sleep -o jsonpath={.items..metadata.name}) $ kubectl exec -it $SOURCE_POD -c sleep curl http://httpbin.org/headers {{< /text >}}

Understanding what happened

In this task you looked at two ways to call external services from an Istio mesh:

  1. Using a ServiceEntry (recommended).

  2. Configuring the Istio sidecar to exclude external IPs from its remapped IP table.

The first approach, using ServiceEntry, lets you use all of the same Istio service mesh features for calls to services inside or outside of the cluster. You saw this by setting a timeout rule for calls to an external service.

The second approach bypasses the Istio sidecar proxy, giving your services direct access to any external URL. However, configuring the proxy this way does require cluster provider specific knowledge and configuration.

Cleanup

  1. Remove the rules:

    {{< text bash >}} $ kubectl delete serviceentry httpbin-ext google $ kubectl delete virtualservice httpbin-ext google {{< /text >}}

  2. Shutdown the [sleep]({{< github_tree >}}/samples/sleep) service:

    {{< text bash >}} $ kubectl delete -f @samples/sleep/sleep.yaml@ {{< /text >}}

  3. Update the ConfigMap istio-sidecar-injector to redirect all outbound traffic to the sidecar proxies:

    {{< text bash >}} $ helm template install/kubernetes/helm/istio -x templates/sidecar-injector-configmap.yaml | kubectl apply -f - {{< /text >}}