orca: cleanup old code, and get grpc package to use new code (#5627)

balancer/balancer.go

@@ -244,7 +244,7 @@ type DoneInfo struct {
 	// ServerLoad is the load received from server. It's usually sent as part of
 	// trailing metadata.
 	//
-	// The only supported type now is *orca_v1.LoadReport.
+	// The only supported type now is *orca_v3.LoadReport.
 	ServerLoad interface{}
 }
 

orca/orca.go

@@ -34,6 +34,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/balancerload"
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
@@ -162,3 +163,24 @@ func ToLoadReport(md metadata.MD) (*v3orcapb.OrcaLoadReport, error) {
 	}
 	return ret, nil
 }
+
+// loadParser implements the Parser interface defined in `internal/balancerload`
+// package. This interface is used by the client stream to parse load reports
+// sent by the server in trailer metadata. The parsed loads are then sent to
+// balancers via balancer.DoneInfo.
+//
+// The grpc package cannot directly call orca.ToLoadReport() as that would cause
+// an import cycle. Hence this roundabout method is used.
+type loadParser struct{}
+
+func (loadParser) Parse(md metadata.MD) interface{} {
+	lr, err := ToLoadReport(md)
+	if err != nil {
+		logger.Errorf("Parse(%v) failed: %v", err)
+	}
+	return lr
+}
+
+func init() {
+	balancerload.SetParser(loadParser{})
+}

xds/internal/balancer/clusterimpl/picker.go

@@ -19,14 +19,15 @@
 package clusterimpl
 
 import (
-	orcapb "github.com/cncf/xds/go/xds/data/orca/v3"
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/internal/wrr"
 	"google.golang.org/grpc/status"
 	"google.golang.org/grpc/xds/internal/xdsclient"
 	"google.golang.org/grpc/xds/internal/xdsclient/load"
+
+	v3orcapb "github.com/cncf/xds/go/xds/data/orca/v3"
 )
 
 // NewRandomWRR is used when calculating drops. It's exported so that tests can
@@ -158,7 +159,7 @@ func (d *picker) Pick(info balancer.PickInfo) (balancer.PickResult, error) {
 			}
 			d.loadStore.CallFinished(lIDStr, info.Err)
 
-			load, ok := info.ServerLoad.(*orcapb.OrcaLoadReport)
+			load, ok := info.ServerLoad.(*v3orcapb.OrcaLoadReport)
 			if !ok {
 				return
 			}