Jul 29, 2017 · 1 min read
The general advice is to not change existing fields on protobuf messages. Add new fields and have update/tell consumers to use the new fields leaving the existing ones in place until you can confirm no consumers are relying on it the you can remove it and reserve the field number.
You can also add a deprecation flag like so, but that is for documentation and does not have any real effect in the proto libraries.
int32 old_field = 6 [deprecated=true];