LinkerD with Headless Service or not?

[pantinor]

In reference to this discussion about the request level load balancing across dynamically scheduled servers and pods:

https://kubernetes.io/blog/2018/11/07/grpc-load-balancing-on-kubernetes-without-tears/

Is it recommended to not use a headless service? and instead use LinkerD and lightweight proxy to load balance the requests cross dynamic pods and gRPC servers in the cluster?

[wmorgan]

Linkerd can only provide load-balancing to regular (non-headless) services. If you have a gRPC service, my recommendation is to make it regular service and use Linkerd. :)

[pantinor]

OK, thats fine. But in this case, for the gRPC client to send a request, the channel shall be established to which host? Can the client target any of the addresses? Normally with a cluster service we would target the clusterIP and port to load balance. SO what shall be the target host when balancing with LinkerD, or does it not matter ?

[olix0r]

When an application connects to a service's clusterIP, the linkerd proxy will do load balancing over the pods in the service (and discover service profiles / traffic splits for the service). When a client targets a pod, linkerd will just forward requests to the pod without doing any service-level routing/loadbalancing/etc.

To be clear: this has nothing to do with the :authority header value and relies solely on the IP address to which the client builds a TCP connection.