什么是 gRPC？

syntax = "proto3";
package userservice.v1;
// User service for managing user accounts
service UserService {
  // Create a new user account
  rpc CreateUser(CreateUserRequest) returns (User);
  
  // Get user by ID
  rpc GetUser(GetUserRequest) returns (User);
  
  // List users with pagination
  rpc ListUsers(ListUsersRequest) returns (ListUsersResponse);
  
  // Update user information
  rpc UpdateUser(UpdateUserRequest) returns (User);
  
  // Delete a user account
  rpc DeleteUser(DeleteUserRequest) returns (google.protobuf.Empty);
  
  // Stream user events (server streaming)
  rpc StreamUserEvents(StreamUserEventsRequest) returns (stream UserEvent);
  
  // Upload user data (client streaming)
  rpc UploadUserData(stream UploadUserDataRequest) returns (UploadUserDataResponse);
  
  // Real-time chat (bidirectional streaming)
  rpc Chat(stream ChatMessage) returns (stream ChatMessage);
}
// Messages for user operations
message User {
  string id = 1;
  string email = 2;
  string name = 3;
  int32 age = 4;
  google.protobuf.Timestamp created_at = 5;
  UserStatus status = 6;
}
message CreateUserRequest {
  string email = 1;
  string name = 2;
  int32 age = 3;
}
message GetUserRequest {
  string id = 1;
}
message ListUsersRequest {
  int32 page_size = 1;
  string page_token = 2;
  string filter = 3;
}
message ListUsersResponse {
  repeated User users = 1;
  string next_page_token = 2;
  int32 total_count = 3;
}
message UpdateUserRequest {
  string id = 1;
  User user = 2;
  google.protobuf.FieldMask update_mask = 3;
}
message DeleteUserRequest {
  string id = 1;
}
message StreamUserEventsRequest {
  string user_id = 1;
  repeated UserEventType event_types = 2;
}
message UserEvent {
  string id = 1;
  string user_id = 2;
  UserEventType type = 3;
  google.protobuf.Timestamp timestamp = 4;
  google.protobuf.Any data = 5;
}
message UploadUserDataRequest {
  oneof data {
    UserDataChunk chunk = 1;
    UserDataMetadata metadata = 2;
  }
}
message UserDataChunk {
  bytes data = 1;
  int64 offset = 2;
}
message UserDataMetadata {
  string filename = 1;
  int64 total_size = 2;
  string content_type = 3;
}
message UploadUserDataResponse {
  string file_id = 1;
  int64 bytes_uploaded = 2;
}
message ChatMessage {
  string id = 1;
  string user_id = 2;
  string room_id = 3;
  string content = 4;
  google.protobuf.Timestamp timestamp = 5;
  ChatMessageType type = 6;
}
// Enums
enum UserStatus {
  USER_STATUS_UNSPECIFIED = 0;
  USER_STATUS_ACTIVE = 1;
  USER_STATUS_INACTIVE = 2;
  USER_STATUS_SUSPENDED = 3;
}
enum UserEventType {
  USER_EVENT_TYPE_UNSPECIFIED = 0;
  USER_EVENT_TYPE_CREATED = 1;
  USER_EVENT_TYPE_UPDATED = 2;
  USER_EVENT_TYPE_DELETED = 3;
  USER_EVENT_TYPE_LOGIN = 4;
  USER_EVENT_TYPE_LOGOUT = 5;
}
enum ChatMessageType {
  CHAT_MESSAGE_TYPE_UNSPECIFIED = 0;
  CHAT_MESSAGE_TYPE_TEXT = 1;
  CHAT_MESSAGE_TYPE_IMAGE = 2;
  CHAT_MESSAGE_TYPE_FILE = 3;
  CHAT_MESSAGE_TYPE_SYSTEM = 4;
}