Add SetTrailer and SetHeader in metadata_interceptor example

Author: purnesh42H

examples/features/metadata_interceptor/client/main.go

@@ -29,18 +29,35 @@ import (
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/metadata"
 
 	pb "google.golang.org/grpc/examples/features/proto/echo"
 )
 
 var addr = flag.String("addr", "localhost:50051", "the address to connect to")
 
 func callUnaryEcho(ctx context.Context, client pb.EchoClient) {
-	resp, err := client.UnaryEcho(ctx, &pb.EchoRequest{Message: "hello world"})
+	var header, trailer metadata.MD // variable to store header and trailer
+	resp, err := client.UnaryEcho(
+		ctx,
+		&pb.EchoRequest{Message: "hello world"},
+		grpc.Header(&header),
+		grpc.Trailer(&trailer))
+
 	if err != nil {
 		log.Fatalf("UnaryEcho: %v", err)
 	}
 	fmt.Println("UnaryEcho: ", resp.Message)
+
+	fmt.Println("Received headers:")
+	for k, v := range header {
+		fmt.Printf("%s: %v\n", k, v)
+	}
+
+	fmt.Println("Received trailers:")
+	for k, v := range trailer {
+		fmt.Printf("%s: %v\n", k, v)
+	}
 }
 
 func callBidiStreamingEcho(ctx context.Context, client pb.EchoClient) {
@@ -54,6 +71,16 @@ func callBidiStreamingEcho(ctx context.Context, client pb.EchoClient) {
 	}
 	c.CloseSend()
 
+	header, err := c.Header()
+	if err != nil {
+		log.Fatalf("Receiving headers: %v", err)
+	} else {
+		fmt.Println("Received headers:")
+		for k, v := range header {
+			fmt.Printf("%s: %v\n", k, v)
+		}
+	}
+
 	for {
 		resp, err := c.Recv()
 		if err == io.EOF {
@@ -64,6 +91,12 @@ func callBidiStreamingEcho(ctx context.Context, client pb.EchoClient) {
 		}
 		fmt.Println("BidiStreaming Echo: ", resp.Message)
 	}
+
+	trailer := c.Trailer()
+	fmt.Println("Received tailers:")
+	for k, v := range trailer {
+		fmt.Printf("%s: %v\n", k, v)
+	}
 }
 
 func main() {

examples/features/metadata_interceptor/server/main.go

@@ -49,10 +49,22 @@ func unaryInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo,
 		return nil, errMissingMetadata
 	}
 
+	// create and set metadata from interceptor to server
 	md.Append("key1", "value1")
 	ctx = metadata.NewIncomingContext(ctx, md)
 
-	return handler(ctx, req)
+	// 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("unary-header-key", "val")
+	grpc.SetHeader(ctx, header)
+
+	// create and set trailer metadata from interceptor to client
+	trailer := metadata.Pairs("unary-trailer-key", "val")
+	grpc.SetTrailer(ctx, trailer)
+
+	return resp, err
 }
 
 func (s *server) UnaryEcho(ctx context.Context, in *pb.EchoRequest) (*pb.EchoResponse, error) {
@@ -89,10 +101,22 @@ func streamInterceptor(srv any, ss grpc.ServerStream, info *grpc.StreamServerInf
 		return errMissingMetadata
 	}
 
+	// create and set metadata from interceptor to server
 	md.Append("key1", "value1")
 	ctx := metadata.NewIncomingContext(ss.Context(), md)
 
-	return handler(srv, &wrappedStream{ss, ctx})
+	// create and set header
+	header := metadata.Pairs("stream-header-key", "val")
+	ss.SetHeader(header)
+
+	// call the handler to complete the normal execution of the RPC
+	err := handler(srv, &wrappedStream{ss, ctx})
+
+	// create and set trailer metadata from interceptor to client
+	trailer := metadata.Pairs("stream-trailer-key", "val")
+	ss.SetTrailer(trailer)
+
+	return err
 }
 
 func (s *server) BidirectionalStreamingEcho(stream pb.Echo_BidirectionalStreamingEchoServer) error {