grpc · menghanl · Apr 2, 2019 · Jan 30, 2019 · Feb 13, 2019
diff --git a/balancer/balancer.go b/balancer/balancer.go
@@ -183,6 +183,11 @@ type DoneInfo struct {
 	BytesSent bool
 	// BytesReceived indicates if any byte has been received from the server.
 	BytesReceived bool
+	// 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.
+	ServerLoad interface{}
 }
 
 var (

diff --git a/internal/balancerload/load.go b/internal/balancerload/load.go
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package balancerload defines APIs to parse server loads in trailers. The
+// parsed loads are sent to balancers in DoneInfo.
+package balancerload
+
+import (
+	"google.golang.org/grpc/metadata"
+)
+
+// Parser converts loads from metadata into a concrete type.
+type Parser interface {
+	// Parse parses loads from metadata.
+	Parse(md metadata.MD) interface{}
+}
+
+var parser Parser
+
+// SetParser sets the load parser.
+//
+// Not mutex-protected, should be called before any gRPC functions.
+func SetParser(lr Parser) {
+	parser = lr
+}
+
+// Parse calls parser.Read().
+func Parse(md metadata.MD) interface{} {
+	if parser == nil {
+		return nil
+	}
+	return parser.Parse(md)
+}
diff --git a/internal/balancerload/orca/orca.go b/internal/balancerload/orca/orca.go
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//go:generate protoc -I ./orca_v1 --go_out=plugins=grpc:./orca_v1 ./orca_v1/orca.proto
+
+// Package orca implements Open Request Cost Aggregation.
+package orca
+
+import (
+	"github.com/golang/protobuf/proto"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/internal/balancerload"
+	orcapb "google.golang.org/grpc/internal/balancerload/orca/orca_v1"
+	"google.golang.org/grpc/metadata"
+)
+
+const mdKey = "X-Endpoint-Load-Metrics-Bin"
+
+// toBytes converts a orca load report into bytes.
+func toBytes(r *orcapb.LoadReport) []byte {
+	if r == nil {
+		return nil
+	}
+
+	b, err := proto.Marshal(r)
+	if err != nil {
+		grpclog.Warningf("orca: failed to marshal load report: %v", err)
+		return nil
+	}
+	return b
+}
+
+// ToMetadata converts a orca load report into grpc metadata.
+func ToMetadata(r *orcapb.LoadReport) metadata.MD {
+	b := toBytes(r)
+	if b == nil {
+		return nil
+	}
+	return metadata.Pairs(mdKey, string(b))
+}
+
+// fromBytes reads load report bytes and converts it to orca.
+func fromBytes(b []byte) *orcapb.LoadReport {
+	ret := new(orcapb.LoadReport)
+	if err := proto.Unmarshal(b, ret); err != nil {
+		grpclog.Warningf("orca: failed to unmarshal load report: %v", err)
+		return nil
+	}
+	return ret
+}
+
+// FromMetadata reads load report from metadata and converts it to orca.
+//
+// It returns nil if report is not found in metadata.
+func FromMetadata(md metadata.MD) *orcapb.LoadReport {
+	vs := md.Get(mdKey)
+	if len(vs) == 0 {
+		return nil
+	}
+	return fromBytes([]byte(vs[0]))
+}
+
+type loadParser struct{}
+
+func (*loadParser) Parse(md metadata.MD) interface{} {
+	return FromMetadata(md)
+}
+
+func init() {
+	balancerload.SetParser(&loadParser{})
+}
diff --git a/internal/balancerload/orca/orca_test.go b/internal/balancerload/orca/orca_test.go
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package orca
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/golang/protobuf/proto"
+	"google.golang.org/grpc/internal/balancerload/orca/orca_v1"
+	"google.golang.org/grpc/metadata"
+)
+
+var (
+	testMessage = &orca_v1.LoadReport{
+		CpuUtilization:           0.1,
+		MemUtilization:           0.2,
+		NicInUtilization:         0,
+		NicOutUtilization:        0,
+		RequestCostOrUtilization: map[string]float64{"ttt": 0.4},
+	}
+	testBytes, _ = proto.Marshal(testMessage)
+)
+
+func TestToMetadata(t *testing.T) {
+	tests := []struct {
+		name string
+		r    *orca_v1.LoadReport
+		want metadata.MD
+	}{{
+		name: "nil",
+		r:    nil,
+		want: nil,
+	}, {
+		name: "valid",
+		r:    testMessage,
+		want: metadata.MD{
+			strings.ToLower(mdKey): []string{string(testBytes)},
+		},
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := ToMetadata(tt.r); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("ToMetadata() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestFromMetadata(t *testing.T) {
+	tests := []struct {
+		name string
+		md   metadata.MD
+		want *orca_v1.LoadReport
+	}{{
+		name: "nil",
+		md:   nil,
+		want: nil,
+	}, {
+		name: "valid",
+		md: metadata.MD{
+			strings.ToLower(mdKey): []string{string(testBytes)},
+		},
+		want: testMessage,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := FromMetadata(tt.md); !proto.Equal(got, tt.want) {
+				t.Errorf("FromMetadata() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}