Installing Istio for Knative

This guide walks you through manually installing and customizing Istio for use with Knative.

If your cloud platform offers a managed Istio installation, we recommend installing Istio that way, unless you need the ability to customize your installation. If your cloud platform offers a managed Istio installation, the install guide for your specific platform will have those instructions.

For example, the GKE Install Guide includes the instructions for installing Istio on your cluster using gcloud.

Before you begin

You need:

  • A Kubernetes cluster created.
  • helm installed.

Installing Istio

When you install Istio, there are a few options depending on your goals. For a basic Istio installation suitable for most Knative use cases, follow the Installing Istio without sidecar injection instructions. If you're familiar with Istio and know what kind of installation you want, read through the options and choose the installation that suits your needs.

You can easily customize your Istio installation with helm. The below sections cover a few useful Istio configurations and their benefits.

Choosing an Istio installation

You can install Istio with or without a service mesh:

  • automatic sidecar injection: Enables the Istio service mesh by automatically injecting the Istio sidecars. The sidecars are injected into each pod of your cluster as they are created.

  • manual sidecar injection: Provides your Knative installation with traffic routing and ingress, without the Istio service mesh. You do have the option of later enabling the service mesh if you manually inject the Istio sidecars.

If you are just getting started with Knative, we recommend installing Istio without automatic sidecar injection.

Downloading Istio and installing CRDs

  1. Enter the following commands to download Istio:

    # Download and unpack Istio
export ISTIO_VERSION=1.3.6
curl -L https://git.io/getLatestIstio | sh -
cd istio-${ISTIO_VERSION}

  2. Enter the following command to install the Istio CRDs first:

    for i in install/kubernetes/helm/istio-init/files/crd*yaml; do kubectl apply -f $i; done

    Wait a few seconds for the CRDs to be committed in the Kubernetes API-server, then continue with these instructions.

  3. Create istio-system namespace

    cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Namespace
metadata:
  name: istio-system
  labels:
    istio-injection: disabled
EOF

  4. Finish the install by applying your desired Istio configuration:

Installing Istio without sidecar injection

If you want to get up and running with Knative quickly, we recommend installing Istio without automatic sidecar injection. This install is also recommended for users who don't need the Istio service mesh, or who want to enable the service mesh by manually injecting the Istio sidecars.

Enter the following command to install Istio:

# A lighter template, with just pilot/gateway.
# Based on install/kubernetes/helm/istio/values-istio-minimal.yaml
helm template --namespace=istio-system \
  --set prometheus.enabled=false \
  --set mixer.enabled=false \
  --set mixer.policy.enabled=false \
  --set mixer.telemetry.enabled=false \
  `# Pilot doesn't need a sidecar.` \
  --set pilot.sidecar=false \
  --set pilot.resources.requests.memory=128Mi \
  `# Disable galley (and things requiring galley).` \
  --set galley.enabled=false \
  --set global.useMCP=false \
  `# Disable security / policy.` \
  --set security.enabled=false \
  --set global.disablePolicyChecks=true \
  `# Disable sidecar injection.` \
  --set sidecarInjectorWebhook.enabled=false \
  --set global.proxy.autoInject=disabled \
  --set global.omitSidecarInjectorConfigMap=true \
  --set gateways.istio-ingressgateway.autoscaleMin=1 \
  --set gateways.istio-ingressgateway.autoscaleMax=2 \
  `# Set pilot trace sampling to 100%` \
  --set pilot.traceSampling=100 \
  --set global.mtls.auto=false \
  install/kubernetes/helm/istio \
  > ./istio-lean.yaml

kubectl apply -f istio-lean.yaml

Installing Istio with sidecar injection

If you want to enable the Istio service mesh, you must enable automatic sidecar injection. The Istio service mesh provides a few benefits:

  • Allows you to turn on mutual TLS, which secures service-to-service traffic within the cluster.

  • Allows you to use the Istio authorization policy, controlling the access to each Knative service based on Istio service roles.

Enter the following command to install Istio:

# A template with sidecar injection enabled.
helm template --namespace=istio-system \
  --set sidecarInjectorWebhook.enabled=true \
  --set sidecarInjectorWebhook.enableNamespacesByDefault=true \
  --set global.proxy.autoInject=disabled \
  --set global.disablePolicyChecks=true \
  --set prometheus.enabled=false \
  `# Disable mixer prometheus adapter to remove istio default metrics.` \
  --set mixer.adapters.prometheus.enabled=false \
  `# Disable mixer policy check, since in our template we set no policy.` \
  --set global.disablePolicyChecks=true \
  --set gateways.istio-ingressgateway.autoscaleMin=1 \
  --set gateways.istio-ingressgateway.autoscaleMax=2 \
  --set gateways.istio-ingressgateway.resources.requests.cpu=500m \
  --set gateways.istio-ingressgateway.resources.requests.memory=256Mi \
  `# More pilot replicas for better scale` \
  --set pilot.autoscaleMin=2 \
  `# Set pilot trace sampling to 100%` \
  --set pilot.traceSampling=100 \
  install/kubernetes/helm/istio \
  > ./istio.yaml

kubectl apply -f istio.yaml

Installing Istio with SDS to secure the ingress gateway

Install Istio with Secret Discovery Service (SDS) to enable a few additional configurations for the gateway TLS. This will allow you to:

  • Dynamically update the gateway TLS with multiple TLS certificates to terminate TLS connections.

  • Use Auto TLS.

The below helm flag is needed in your helm command to enable SDS:

--set gateways.istio-ingressgateway.sds.enabled=true

Enter the following command to install Istio with ingress SDS and automatic sidecar injection:

helm template --namespace=istio-system \
  --set sidecarInjectorWebhook.enabled=true \
  --set sidecarInjectorWebhook.enableNamespacesByDefault=true \
  --set global.proxy.autoInject=disabled \
  --set global.disablePolicyChecks=true \
  --set prometheus.enabled=false \
  `# Disable mixer prometheus adapter to remove istio default metrics.` \
  --set mixer.adapters.prometheus.enabled=false \
  `# Disable mixer policy check, since in our template we set no policy.` \
  --set global.disablePolicyChecks=true \
  --set gateways.istio-ingressgateway.autoscaleMin=1 \
  --set gateways.istio-ingressgateway.autoscaleMax=2 \
  --set gateways.istio-ingressgateway.resources.requests.cpu=500m \
  --set gateways.istio-ingressgateway.resources.requests.memory=256Mi \
  `# Enable SDS in the gateway to allow dynamically configuring TLS of gateway.` \
  --set gateways.istio-ingressgateway.sds.enabled=true \
  `# More pilot replicas for better scale` \
  --set pilot.autoscaleMin=2 \
  `# Set pilot trace sampling to 100%` \
  --set pilot.traceSampling=100 \
  install/kubernetes/helm/istio \
  > ./istio.yaml

  kubectl apply -f istio.yaml

Updating your install to use cluster local gateway

If you want your Routes to be visible only inside the cluster, you may want to enable cluster local routes. To use this feature, add an extra Istio cluster local gateway to your cluster. Enter the following command to add the cluster local gateway to an existing Istio installation:

# Add the extra gateway.
helm template --namespace=istio-system \
  --set gateways.custom-gateway.autoscaleMin=1 \
  --set gateways.custom-gateway.autoscaleMax=2 \
  --set gateways.custom-gateway.cpu.targetAverageUtilization=60 \
  --set gateways.custom-gateway.labels.app='cluster-local-gateway' \
  --set gateways.custom-gateway.labels.istio='cluster-local-gateway' \
  --set gateways.custom-gateway.type='ClusterIP' \
  --set gateways.istio-ingressgateway.enabled=false \
  --set gateways.istio-egressgateway.enabled=false \
  --set gateways.istio-ilbgateway.enabled=false \
  --set global.mtls.auto=false \
  install/kubernetes/helm/istio \
  -f install/kubernetes/helm/istio/example-values/values-istio-gateways.yaml \
  | sed -e "s/custom-gateway/cluster-local-gateway/g" -e "s/customgateway/clusterlocalgateway/g" \
  > ./istio-local-gateway.yaml

kubectl apply -f istio-local-gateway.yaml

Alternatively, if you want to install the cluster local gateway for development purposes, enter the following command without helm for an easy installation:

# Istio minor version should be 1.3, 1.4 or 1.5
export ISTIO_MINOR_VERSION=1.3

export VERSION=$(curl https://raw.githubusercontent.com/knative/serving/master/third_party/istio-${ISTIO_MINOR_VERSION}-latest)

kubectl apply -f https://raw.githubusercontent.com/knative/serving/master/third_party/${VERSION}/istio-knative-extras.yaml

Note: This method is only for development purposes. The production readiness of the above installation method is not ensured. For a production-ready installation, see the helm installation method above.

Verifying your Istio install

View the status of your Istio installation to make sure the install was successful. It might take a few seconds, so rerun the following command until all of the pods show a STATUS of Running or Completed:

kubectl get pods --namespace istio-system

Tip: You can append the --watch flag to the kubectl get commands to view the pod status in realtime. You use CTRL + C to exit watch mode.

Configuring DNS

Knative dispatches to different services based on their hostname, so it greatly simplifies things to have DNS properly configured. For this, we must look up the external IP address that Istio received. This can be done with the following command:

$ kubectl get svc -nistio-system
NAME                    TYPE           CLUSTER-IP   EXTERNAL-IP    PORT(S)                                      AGE
cluster-local-gateway   ClusterIP      10.0.2.216   <none>         15020/TCP,80/TCP,443/TCP                     2m14s
istio-ingressgateway    LoadBalancer   10.0.2.24    34.83.80.117   15020:32206/TCP,80:30742/TCP,443:30996/TCP   2m14s
istio-pilot             ClusterIP      10.0.3.27    <none>         15010/TCP,15011/TCP,8080/TCP,15014/TCP       2m14s

This external IP can be used with your DNS provider with a wildcard A record; however, for a basic functioning DNS setup (not suitable for production!) this external IP address can be used with xip.io in the config-domain ConfigMap in knative-serving. You can edit this with the following command:

kubectl edit cm config-domain --namespace knative-serving

Given the external IP above, change the content to:

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-domain
  namespace: knative-serving
data:
  # xip.io is a "magic" DNS provider, which resolves all DNS lookups for:
  # *.{ip}.xip.io to {ip}.
  34.83.80.117.xip.io: ""

Istio resources

Clean up Istio

Enter the following command to remove all of the Istio files:

cd ../
rm -rf istio-${ISTIO_VERSION}

What's next