[zeromq-dev] multi-part messages

[Pieter Hintjens]

On Mon, Jan 23, 2012 at 6:45 PM, Martin Sustrik <sustrik at 250bpm.com> wrote:

> It's a backward incompatible change. The problem with backward
> incompatible changes is that you can do them only so often, if at all.
> The reason being that you are forcing 1000s of users through the pain of
> upgrading, rewriting their application code, re-testing etc.

Well... this is just a matter of will power. There is no reason new
features have to break old ones.

Say you want to introduce labels. What you do first is allow the
protocol to support these without breaking. There have been proposals
for that, we can revisit them if needed. Second, you expose labels via
NEW socket types so you don't break old code. Third, as the new
features become stable you deprecate the old features. Finally, some
years later, you remove them.

This is tried and tested practice. The fault with 3.0 and 4.x was
ignoring cost/benefit and simply breaking old code with no attempt to
provide an upgrade path. That's what people disliked, and that's why
those branches were not used.

-Pieter