关于衍生信息的规范咨询：关联实体信息服务场景疑问

Great question! When building a service that handles related entity data (like your school database-style gRPC setup), there are several well-established patterns and best practices for handling derived information. Let’s walk through the most common approaches tailored to your use case:

1. Embed Lightweight Derived Data Directly in the Core Entity #

If the derived information is small, frequently accessed, and doesn’t require full entity details, you can add it directly to your ClassRoom message. This avoids extra RPC calls and reduces latency for common use cases.

For example, if you often need basic student names associated with a classroom:

message ClassRoom {
  string id = 1;
  string address = 2;
  string teacher = 3;
  // Derived data: minimal student details for quick reference
  repeated BasicStudent associated_students = 4;
}

message BasicStudent {
  string id = 1;
  string full_name = 2;
}

Note: Only use this for small, stable derived data—avoid bloating the core message with large or frequently changing fields.

2. Create Dedicated RPCs for Detailed Derived Data #

For heavier or full-detail derived information (like complete student profiles, classroom equipment lists, or associated courses), it’s better to implement separate RPCs. This follows the single responsibility principle and keeps your service focused.

Update your service definition like this:

service MySchool {
  rpc GetClassRoom (ClassRoomRequest) returns (ClassRoom);
  rpc GetStudent (StudentRequest) returns (Student);
  // New RPC to fetch all full student profiles for a classroom
  rpc GetStudentsInClassRoom (ClassRoomRequest) returns (StudentList);
  // Optional: RPC to get classroom equipment (another derived data type)
  rpc GetClassRoomEquipment (ClassRoomRequest) returns (EquipmentList);
}

message StudentList {
  repeated Student students = 1;
}

message EquipmentList {
  repeated Equipment items = 1;
}

This approach makes your service easy to maintain—each RPC does one clear thing—and lets clients request only the data they need.

3. Use an "Include" Parameter for On-Demand Derived Data #

If you want to keep your core GetClassRoom RPC flexible, add an optional parameter to let clients specify which derived data to include in the response. This balances flexibility and performance.

Example request and response:

message ClassRoomRequest {
  string id = 1;
  // Optional: list of derived data sets to include (e.g., "students", "teacher_details")
  repeated string include = 2;
}

message ClassRoom {
  string id = 1;
  string address = 2;
  string teacher = 3;
  // Optional derived fields—only populated if requested in the include parameter
  repeated Student students = 4;
  TeacherFullDetails teacher_details = 5;
}

Pro tip: Document the valid values for the include parameter clearly in your proto comments so clients know what options they have.

4. Stream Derived Data for Real-Time Use Cases #

If your derived information is real-time (like classroom occupancy, live attendance updates), use gRPC streaming RPCs to push updates to clients continuously.

Example:

service MySchool {
  rpc GetClassRoom (ClassRoomRequest) returns (ClassRoom);
  rpc GetStudent (StudentRequest) returns (Student);
  // Stream real-time occupancy data for a classroom
  rpc StreamClassRoomOccupancy (ClassRoomRequest) returns (stream OccupancyUpdate);
}

message OccupancyUpdate {
  string class_room_id = 1;
  int32 current_student_count = 2;
  google.protobuf.Timestamp update_time = 3;
}

Key Best Practices to Follow #

• Avoid Overloading Core Messages: Don’t cram every possible derived field into your base ClassRoom message—this will slow down calls and make maintenance harder.
• Document Everything: Add comments to your proto files explaining which fields are derived, how they’re populated, and when to use each RPC.
• Optimize for Performance: If derived data requires expensive database joins or external calls, implement caching to reduce latency for repeated requests.
• Stick to Proto Versioning Rules: When adding new derived fields, use unused field numbers and avoid removing or renaming existing fields to prevent breaking existing clients.

内容的提问来源于stack exchange，提问作者Pablo