Support ClientSideWeightedRoundRobin LB policy

[anton-kuklin]

In v1.32.0 Envoy added support for ClientSideWeightedRoundRobin load balancing policy (link).

It would be great to support it in contour.

[github-actions]

Hey @anton-kuklin! Thanks for opening your first issue. We appreciate your contribution and welcome you to our community! We are glad to have you here and to have your input on Contour. You can also join us on our mailing list and in our channel in the Kubernetes Slack Workspace

[tsaarni]

I recently caught a lightning talk about this at EnvoyCon (link to presentation). Have you, by any chance, seen any example code for a backend that sends ORCA reports?

[anton-kuklin]

I recently caught a lightning talk about this at EnvoyCon (link to presentation). Have you, by any chance, seen any example code for a backend that sends ORCA reports?

Hey @tsaarni, yeah, we are using it in a few places natively and I ran a few manual experiments based on the linked PR.

For the in-bound weights reporting the simple example would be (full example link):

func (s *server) UnaryEcho(ctx context.Context, in *pb.EchoRequest) (*pb.EchoResponse, error) {
	// Report a sample cost for this query.
	cmr := orca.CallMetricsRecorderFromContext(ctx)
	if cmr == nil {
		return nil, status.Errorf(codes.Internal, "unable to retrieve call metrics recorder (missing ORCA ServerOption?)")
	}
	cmr.SetRequestCost("db_queries", 10)

	return &pb.EchoResponse{Message: in.Message}, nil
}

And the weight calculation formula on the client is (source link).

$$weight = \dfrac{qps}{utilization + \dfrac{eps}{qps} * error\_utilization\_penalty}$$

[nageshs28]

@sunjayBhatia Are we planning to support this in 1.33 release? Any timelines for 1.33.0 release?