Comment by teacup50 | Hacker News Reader

Comment by teacup50 | Hacker News Reader

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> A canonical example is that you add a required field ...

Yeah. Don't do that without versioning your protocol. It's even less difficult to handle than maintaining API/ABI compatibility in a library.

> So practically speaking, you can never add required fields to any message where you can't guarantee binary version syncing amongst all instances of the message-dependent services.

Sure you can. If you version things at the protocol or per-request level, you can negotiate protocol conformance just fine.

Having a message type defined as "Message_V1" OR "Message_V2" is still simpler than having "any or none of the fields from any iteration of the message definition, where consistency is solely defined in terms of the field/message validation code you write in every protocol consumer".

> And if you're not running an RPC-based service architecture, then why are you using protos anyway?

It's a very serviceable compact serialization mechanism for at-rest data.

> Yeah. Don't do that without versioning your protocol. It's even less difficult to handle than maintaining API/ABI compatibility in a library.

Actually, the whole point of that was so you don't have to version your protocol. Protocol versioning actually tends to make code maintenance a pain in the posterior, and working through old data really annoying. Instead, you do optional fields.

If you don't want that, go ahead and just write raw bytes and don't bother with the serialization layer.

> Having a message type defined as "Message_V1" OR "Message_V2" is still simpler than having "any or none of the fields from any iteration of the message definition, where consistency is solely defined in terms of the field/message validation code you write in every protocol consumer".

But you don't have to do either. It seems like you aren't familiar with the use of protocol buffers. You just define optional fields with a reasonable default, and magically all the old protobufs get that default value.

> If you don't want that, go ahead and just write raw bytes and don't bother with the serialization layer.

Or just keep using protobuf2, 'cause it's been working great for us for ~6 years.

> But you don't have to do either. It seems like you aren't familiar with the use of protocol buffers.

I've written my own protobuf compiler. I'm familiar.

> You just define optional fields with a reasonable default, and magically all the old protobufs get that default value.

That only works up until there's no "reasonable default".

> Or just keep using protobuf2, 'cause it's been working great for us for ~6 years.

Oh sure, I wouldn't change practices, but I'd certain question why that practice had been put in place.

> That only works up until there's no "reasonable default".

If there is no reasonable default, I'd be even more wary about making it a required field.

> It's a very serviceable compact serialization mechanism for at-rest data.

That's fair, but then you run into the same issue -- adding required a field requires updating your entire store.

Depending on your store, that can range from onerous to outright impossible.

> Don't do that without versioning your protocol

I think it depends on your needs, but I think for most users, explicit versioning of messages is overkill and is just a more heavy way of encoding the same logic (e.g. I saw an older message, I will implicitly upgrade it by filling in these new fields, vs. just looking for the optional field that I just added)

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