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

examples/features/metadata_interceptor/server/main.go

@@ -0,0 +1,164 @@
+/*
+ *
+ * Copyright 2022 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 update metadata from interceptors on server.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net"
+
+	"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")
+
+var errMissingMetadata = status.Errorf(codes.InvalidArgument, "no incoming metadata in rpc context")
+
+type server struct {
+	pb.UnimplementedEchoServer
+}
+
+func unaryInterceptor(ctx context.Context, req any, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, errMissingMetadata
+	}
+
+	// Create and set metadata from interceptor to server.
+	md.Append("key1", "value1")
+	ctx = metadata.NewIncomingContext(ctx, md)
+
+	// Call the handler to complete the normal execution of the RPC.
+	resp, err := handler(ctx, req)
+
+	// Create and set header metadata from interceptor to client.
+	header := metadata.Pairs("header-key", "val")
+	grpc.SetHeader(ctx, header)
+
+	// Create and set trailer metadata from interceptor to client.
+	trailer := metadata.Pairs("trailer-key", "val")
+	grpc.SetTrailer(ctx, trailer)
+
+	return resp, err
+}
+
+func (s *server) UnaryEcho(ctx context.Context, in *pb.EchoRequest) (*pb.EchoResponse, error) {
+	fmt.Printf("--- UnaryEcho ---\n")
+
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return nil, status.Errorf(codes.Internal, "UnaryEcho: missing incoming metadata in rpc context")
+	}
+
+	// Read and print metadata added by the interceptor.
+	if v, ok := md["key1"]; ok {
+		fmt.Printf("key1 from metadata: \n")
+		for i, e := range v {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	return &pb.EchoResponse{Message: in.Message}, nil
+}
+
+type wrappedStream struct {
+	grpc.ServerStream
+	ctx context.Context
+}
+
+func (s *wrappedStream) Context() context.Context {
+	return s.ctx
+}
+
+func streamInterceptor(srv any, ss grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+	md, ok := metadata.FromIncomingContext(ss.Context())
+	if !ok {
+		return errMissingMetadata
+	}
+
+	// Create and set metadata from interceptor to server.
+	md.Append("key1", "value1")
+	ctx := metadata.NewIncomingContext(ss.Context(), md)
+
+	// Call the handler to complete the normal execution of the RPC.
+	err := handler(srv, &wrappedStream{ss, ctx})
+
+	// Create and set header metadata from interceptor to client.
+	header := metadata.Pairs("header-key", "val")
+	ss.SetHeader(header)
+
+	// Create and set trailer metadata from interceptor to client.
+	trailer := metadata.Pairs("trailer-key", "val")
+	ss.SetTrailer(trailer)
+
+	return err
+}
+
+func (s *server) BidirectionalStreamingEcho(stream pb.Echo_BidirectionalStreamingEchoServer) error {
+	fmt.Printf("--- BidirectionalStreamingEcho ---\n")
+
+	md, ok := metadata.FromIncomingContext(stream.Context())
+	if !ok {
+		return status.Errorf(codes.Internal, "BidirectionalStreamingEcho: missing incoming metadata in rpc context")
+	}
+
+	// Read and print metadata added by the interceptor.
+	if v, ok := md["key1"]; ok {
+		fmt.Printf("key1 from metadata: \n")
+		for i, e := range v {
+			fmt.Printf(" %d. %s\n", i, e)
+		}
+	}
+
+	// Read requests and send responses.
+	for {
+		in, err := stream.Recv()
+		if err == io.EOF {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		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("net.Listen() failed: %v", err)
+	}
+	fmt.Printf("Server listening at %v\n", lis.Addr())
+
+	s := grpc.NewServer(grpc.UnaryInterceptor(unaryInterceptor), grpc.StreamInterceptor(streamInterceptor))
+	pb.RegisterEchoServer(s, &server{})
+	s.Serve(lis)
+}