Code snippets — Grpc Vs Rest

snippet-2.go

func (s *server) Chat(stream pb.ChatService_ChatServer) error {
    for {
        msg, err := stream.Recv()
        if err == io.EOF {
            return nil
        }
        // Broadcast to other users...
        stream.Send(&pb.ChatMessage{Content: "echoed: " + msg.Content})
    }
}

snippet-2.sh

# Inspect available services
grpcurl -plaintext localhost:50051 list

# Call a method
grpcurl -plaintext -d '{"user_id": "42"}' \
  localhost:50051 user.UserService/GetUser

snippet-2.txt

Client → Request → Server
Client ← Response ←
Client ← Response ←
Client ← Response ← Server (stream)

snippet-3.go

// Server
func main() {
    lis, err := net.Listen("tcp", ":50051")
    if err != nil {
        log.Fatalf("failed to listen: %v", err)
    }

    s := grpc.NewServer(
        grpc.UnaryInterceptor(authInterceptor),
        grpc.MaxRecvMsgSize(1024*1024*4),
    )

    pb.RegisterUserServiceServer(s, &UserServiceServer{db: db})
    reflection.Register(s)  // Enable grpcurl inspection

    log.Printf("gRPC server listening on :50051")
    s.Serve(lis)
}

// Client
func main() {
    conn, err := grpc.Dial("localhost:50051",
        grpc.WithTransportCredentials(insecure.NewCredentials()),
    )
    defer conn.Close()

    client := pb.NewUserServiceClient(conn)

    ctx, cancel := context.WithTimeout(context.Background(), time.Second)
    defer cancel()

    user, err := client.GetUser(ctx, &pb.GetUserRequest{UserId: "42"})
    fmt.Printf("Got user: %v\n", user)
}

snippet-3.txt

Browser/Mobile → REST (via API Gateway) → Internal Services via gRPC

snippet.go

// Server streaming example
func (s *server) ListUsers(req *pb.ListUsersRequest, stream pb.UserService_ListUsersServer) error {
    rows, err := db.QueryUsers(req.Filter)
    for rows.Next() {
        user := scanUser(rows)
        if err := stream.Send(user); err != nil {
            return err
        }
    }
    return nil
}

snippet.proto

// user.proto
syntax = "proto3";

package user;

service UserService {
  rpc GetUser(GetUserRequest) returns (User);
  rpc ListUsers(ListUsersRequest) returns (stream User);
  rpc CreateUser(CreateUserRequest) returns (User);
}

message GetUserRequest {
  string user_id = 1;
}

message User {
  string id = 1;
  string name = 2;
  string email = 3;
  int64 created_at = 4;
}

snippet.sh

protoc --go_out=. --go-grpc_out=. user.proto

snippet.txt

Client → Request → Server
Client ← Response ← Server