Creating a private cluster-local service

By default services deployed through Knative are published to an external IP address, making them public services on a public IP address and with a public URL.

While this is useful for services that need to be accessible from outside of the cluster, frequently you may be building a backend service which should not be available off-cluster.

Knative provides two ways to enable private services which are only available inside the cluster:

  1. To make all services only cluster-local, change the default domain to svc.cluster.local by editing the config-domain config map. This will change all services deployed through Knative to only be published to the cluster, none will be available off-cluster.
  2. To make an individual service cluster-local, the service or route can be labeled in such a way to prevent it from getting published to the external gateway.

Label a service to be cluster-local

To configure a Knative service to only be available on the cluster-local network (and not on the public Internet), you can apply the label to the Knative service, route or Kubernetes service object.

To label the Knative service:

kubectl label kservice ${KSVC_NAME}

To label a route when the route is used directly without a Knative service:

kubectl label route ${ROUTE_NAME}

To label a Kubernetes service:

kubectl label service ${SERVICE_NAME}

By labeling the Kubernetes service it allows you to restrict visibility in a more fine-grained way. See subroutes for information about tagged routes.

For example, you can deploy the Hello World sample and then convert it to be an cluster-local service by labeling the service:

kubectl label kservice helloworld-go

You can then verify that the change has been made by verifying the URL for the helloworld-go service:

kubectl get kservice helloworld-go

NAME            URL                                              LATESTCREATED         LATESTREADY           READY   REASON
helloworld-go   http://helloworld-go.default.svc.cluster.local   helloworld-go-2bz5l   helloworld-go-2bz5l   True

The service returns the a URL with the svc.cluster.local domain, indicating the service is only available in the cluster local network.