Installing Istio for Knative

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 to customize your installation.

Before you begin

You need:

A Kubernetes cluster created.
istioctl installed.

Supported Istio versions

The current known-to-be-stable version of Istio tested in conjunction with Knative is v1.9.5. Versions in the 1.9 line are generally fine too.

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 istioctl. The following sections cover a few useful Istio configurations and their benefits.

Choosing an Istio installation

You can install Istio with or without a service mesh:

Installing Istio without sidecar injection(Recommended default installation)
Installing Istio with 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.

Installing Istio without sidecar injection

Enter the following command to install Istio:

To install Istio without sidecar injection:

Create a istio-minimal-operator.yaml file using the following template:

apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
  values:
    global:
      proxy:
        autoInject: disabled
      useMCP: false
      # The third-party-jwt is not enabled on all k8s.
      # See: https://istio.io/docs/ops/best-practices/security/#configure-third-party-service-account-tokens
      jwtPolicy: first-party-jwt
  addonComponents:
    pilot:
      enabled: true
  components:
    ingressGateways:
      - name: istio-ingressgateway
        enabled: true

Apply the YAML file by running the command:

istioctl install -f istio-minimal-operator.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.

For automatic sidecar injection, set autoInject: enabled in addition to the earlier operator configuration.

    global:
      proxy:
        autoInject: enabled

Using Istio mTLS feature

Since there are some networking communications between knative-serving namespace and the namespace where your services running on, you need additional preparations for mTLS enabled environment.

Enable sidecar container on knative-serving system namespace.

kubectl label namespace knative-serving istio-injection=enabled

Set PeerAuthentication to PERMISSIVE on knative-serving system namespace by creating a YAML file using the following template:

apiVersion: "security.istio.io/v1beta1"
kind: "PeerAuthentication"
metadata:
  name: "default"
  namespace: "knative-serving"
spec:
  mtls:
    mode: PERMISSIVE

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

After you install the cluster local gateway, your service and deployment for the local gateway is named knative-local-gateway.

Updating the `config-istio` configmap to use a non-default local gateway

If you create a custom service and deployment for local gateway with a name other than knative-local-gateway, you need to update gateway configmap config-istio under the knative-serving namespace.

Edit the config-istio configmap:

kubectl edit configmap config-istio -n knative-serving

Replace the local-gateway.knative-serving.knative-local-gateway field with the custom service. As an example, if you name both the service and deployment custom-local-gateway under the namespace istio-system, it should be updated to:
```
custom-local-gateway.istio-system.svc.cluster.local
```

As an example, if both the custom service and deployment are labeled with custom: custom-local-gateway, not the default istio: knative-local-gateway, you must update gateway instance knative-local-gateway in the knative-serving namespace:

kubectl edit gateway knative-local-gateway -n knative-serving

Replace the label selector with the label of your service:

istio: knative-local-gateway

For the service mentioned earlier, it should be updated to:

custom: custom-local-gateway

If there is a change in service ports (compared to that of knative-local-gateway), update the port info in the gateway accordingly.

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 is recommended to have DNS properly configured.

To do this, begin by looking up the external IP address that Istio received:

$ kubectl get svc -nistio-system
NAME                    TYPE           CLUSTER-IP   EXTERNAL-IP    PORT(S)                                      AGE
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 non-production set up, this external IP address can be used with sslip.io in the config-domain ConfigMap in knative-serving.

You can edit this by using the following command:

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

Given this external IP, change the content to:

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

Istio resources

For the official Istio installation guide, see the Istio Kubernetes Getting Started Guide.
For the full list of available configs when installing Istio with istioctl, see the Istio Installation Options reference.