How did you approach versioning gRPC contracts?

Versioning of gRPC contracts in Golang is usually based on the following principles:

• Backward Compatibility: we try not to break existing services and clients.
• Adding new methods and messages: new RPCs and fields are added with new numbers, old ones are not removed.
• Using optional fields: new fields in messages are made optional so that old clients can ignore them.
• Versioning of packages or services: sometimes separate packages with versions are created, for example v1, v2, to clearly distinguish different API versions.

Example:

syntax = "proto3";
package example.v1;

service MyService {
  rpc GetData(Request) returns (Response);
}

message Request {
  int32 id = 1;
}

message Response {
  string data = 1;
  string extra_info = 2; // new optional field
}

If an incompatible change is needed, a new version of the service is created, for example example.v2.MyService.

Thus, clients can gradually migrate to the new version without interruption.