How do I represent a UUID in a protobuf message?

Question

I want to attach a UUID to a field in my protobuf User message example.

message User {
  // field containing id as UUID type
  required string email;
  optio         


        

Answer 1

If anything, you want to use string to avoid problems with endianness. Note that a UUID and a MS GUID that have the same string representation (and therefore are the same "id") have, however, different byte-stream order (big-endian vs little-endian). If you use bytes in the protocol to communicate between Java using UUID and C# using System.Guid, you could end up with flipped IDs.

Answer 2

You should probably use string or bytes to represent a UUID. Use string if it is most convenient to keep the UUID in human-readable format (e.g. "de305d54-75b4-431b-adb2-eb6b9e546014") or use bytes if you are storing the 128-bit value raw. (If you aren't sure, you probably want string.)

Wrapping the value in a message type called UUID can be helpful to make the code more self-documenting but will have some performance overhead and isn't strictly required. If you want to do this, define the type like:

message UUID {
  required string value = 1;
}

or:

message UUID {
  required bytes value = 1;
}

Answer 3

I don't have enough reputation points to make a comment, so I have to write this as an answer.

Use a string, not a byte array unlike what some other commenters are saying. According to MS (https://docs.microsoft.com/en-us/dotnet/architecture/grpc-for-wcf-developers/protobuf-data-types), "Don't use a bytes field for Guid values. Problems with endianness (Wikipedia definition) can result in erratic behavior when Protobuf is interacting with other platforms, such as Java."