Add Leader Service

[TaeSooRhee-moreh]

What would you like to be added:
Make ClusterIP leader service with network config

Why is this needed:
As we can see from examples, we usually need service for leaders.

Completion requirements:
Add Spec.NetworkConfig.LeaderServicePort to make ClusterIP

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[ahg-g]

Hi Tae, Service is not necessarily the only way to expose a LWS replicas for load balancing, there is no need to create this coupling. Just like Deployment doesn't create a Service by default, LWS doesn't either.

[TaeSooRhee-moreh]

Hi @ahg-g, and thanks for your reply.
If we say that a Deployment does not create a Service, then LWS also shouldn’t make any other Service.
However, since LWS already creates a Headless Service, I think it would be fine to optionally create an additional Service with leaders.
Since most examples also create a ClusterIP Service for the leaders, it would be convenient to create it together as well.
Still, if you feel it’s not really needed, we can just close the issue. Thanks!

[ahg-g]

However, since LWS already creates a Headless Service, I think it would be fine to optionally create an additional Service with leaders.

The headlesss service that LWS creates is pretty much the only and standard way to create stable dns hostnames, anyone using LWS doesn't need to be aware of that headless service, so it is really an implementation detail and hence it is automated.

The above is not the case for how to expose LWS replicas for serving.