snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

examples/features/metadata/server/main.go

@@ -0,0 +1,208 @@
+/*
+ *
+ * Copyright 2018 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.
+ *
+ */
+
+// Binary server demonstrates how to send and read metadata to and from RPC.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+)
+
+var port = flag.Int("port", 50051, "the port to serve on")
+
+const (
+	timestampFormat = time.StampNano
+	streamingCount  = 10
+)
+
+type server struct {
+	pb.UnimplementedEchoServer
+}
+
+func (s *server) UnaryEcho(ctx context.Context, in *pb.EchoRequest) (*pb.EchoResponse, error) {
+	fmt.Printf("--- UnaryEcho ---\n")
+	// Create trailer in defer to record function return time.
+	defer func() {
+		trailer := metadata.Pairs("timestamp", time.Now().Format(timestampFormat))
+		grpc.SetTrailer(ctx, trailer)
+	}()
+
+	// Read metadata from client.
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, status.Errorf(codes.DataLoss, "UnaryEcho: failed to get metadata")
+	}
+	if t, ok := md["timestamp"]; ok {
+		fmt.Printf("timestamp from metadata:\n")
+		for i, e := range t {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	// Create and send header.
+	header := metadata.New(map[string]string{"location": "MTV", "timestamp": time.Now().Format(timestampFormat)})
+	grpc.SendHeader(ctx, header)
+
+	fmt.Printf("request received: %v, sending echo\n", in)
+
+	return &pb.EchoResponse{Message: in.Message}, nil
+}
+
+func (s *server) ServerStreamingEcho(in *pb.EchoRequest, stream pb.Echo_ServerStreamingEchoServer) error {
+	fmt.Printf("--- ServerStreamingEcho ---\n")
+	// Create trailer in defer to record function return time.
+	defer func() {
+		trailer := metadata.Pairs("timestamp", time.Now().Format(timestampFormat))
+		stream.SetTrailer(trailer)
+	}()
+
+	// Read metadata from client.
+	md, ok := metadata.FromIncomingContext(stream.Context())
+	if !ok {
+		return status.Errorf(codes.DataLoss, "ServerStreamingEcho: failed to get metadata")
+	}
+	if t, ok := md["timestamp"]; ok {
+		fmt.Printf("timestamp from metadata:\n")
+		for i, e := range t {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	// Create and send header.
+	header := metadata.New(map[string]string{"location": "MTV", "timestamp": time.Now().Format(timestampFormat)})
+	stream.SendHeader(header)
+
+	fmt.Printf("request received: %v\n", in)
+
+	// Read requests and send responses.
+	for i := 0; i < streamingCount; i++ {
+		fmt.Printf("echo message %v\n", in.Message)
+		err := stream.Send(&pb.EchoResponse{Message: in.Message})
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (s *server) ClientStreamingEcho(stream pb.Echo_ClientStreamingEchoServer) error {
+	fmt.Printf("--- ClientStreamingEcho ---\n")
+	// Create trailer in defer to record function return time.
+	defer func() {
+		trailer := metadata.Pairs("timestamp", time.Now().Format(timestampFormat))
+		stream.SetTrailer(trailer)
+	}()
+
+	// Read metadata from client.
+	md, ok := metadata.FromIncomingContext(stream.Context())
+	if !ok {
+		return status.Errorf(codes.DataLoss, "ClientStreamingEcho: failed to get metadata")
+	}
+	if t, ok := md["timestamp"]; ok {
+		fmt.Printf("timestamp from metadata:\n")
+		for i, e := range t {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	// Create and send header.
+	header := metadata.New(map[string]string{"location": "MTV", "timestamp": time.Now().Format(timestampFormat)})
+	stream.SendHeader(header)
+
+	// Read requests and send responses.
+	var message string
+	for {
+		in, err := stream.Recv()
+		if err == io.EOF {
+			fmt.Printf("echo last received message\n")
+			return stream.SendAndClose(&pb.EchoResponse{Message: message})
+		}
+		message = in.Message
+		fmt.Printf("request received: %v, building echo\n", in)
+		if err != nil {
+			return err
+		}
+	}
+}
+
+func (s *server) BidirectionalStreamingEcho(stream pb.Echo_BidirectionalStreamingEchoServer) error {
+	fmt.Printf("--- BidirectionalStreamingEcho ---\n")
+	// Create trailer in defer to record function return time.
+	defer func() {
+		trailer := metadata.Pairs("timestamp", time.Now().Format(timestampFormat))
+		stream.SetTrailer(trailer)
+	}()
+
+	// Read metadata from client.
+	md, ok := metadata.FromIncomingContext(stream.Context())
+	if !ok {
+		return status.Errorf(codes.DataLoss, "BidirectionalStreamingEcho: failed to get metadata")
+	}
+
+	if t, ok := md["timestamp"]; ok {
+		fmt.Printf("timestamp from metadata:\n")
+		for i, e := range t {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	// Create and send header.
+	header := metadata.New(map[string]string{"location": "MTV", "timestamp": time.Now().Format(timestampFormat)})
+	stream.SendHeader(header)
+
+	// Read requests and send responses.
+	for {
+		in, err := stream.Recv()
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		fmt.Printf("request received %v, sending echo\n", in)
+		if err := stream.Send(&pb.EchoResponse{Message: in.Message}); err != nil {
+			return err
+		}
+	}
+}
+
+func main() {
+	flag.Parse()
+	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
+	if err != nil {
+		log.Fatalf("failed to listen: %v", err)
+	}
+	fmt.Printf("server listening at %v\n", lis.Addr())
+
+	s := grpc.NewServer()
+	pb.RegisterEchoServer(s, &server{})
+	s.Serve(lis)
+}