Be able to whitelist only certain Kubernetes namespace(s)

[igor-vovk]

Hi!

In one of our Kubernetes clusters we deploy the same infrastructure under different Kubernetes namespaces (basically different dev envs). Right now we install XDS in each Kubernetes namespace, as a part of general list of services. But then each of XDS services gathers all services that are in the Kubernetes cluster, which means that services, exposing the same GRPC API, but are in different namespaces, are gathered and then returned by the XDS.

Currently we overcame this problem by using different virtual gateways (in each Kubernetes namespace services advertise their GRPC APIs with different namespace-specific xds.lmwn.com/api-gateway annotation), but would be great to have an option to limit the services gathered by XDS server by specifying certain namespace(s), on the XDS server level.

I wonder what do you think about this idea?