[zeromq-dev] Newbie Bait Request: Debug "Warning" mechanism.

[Alexey Ermakov]

On Wed, Aug 18, 2010 at 12:48 PM, Pieter Hintjens <ph at imatix.com> wrote:
> OK, so we can solve this using the principle of least surprise.
>
> We have a large class of simple pubsub scenarios where the best
> metaphor is (arguably) "start broad, narrow it down".
>
> We have a smaller subset of sophisticated pubsub scenarios where the
> best metaphor is "start with nothing, then add/remove subscriptions".

I'm not sure if I agree with that. Pubsub seems to imply “start with
nothing, then add/remove subscriptions” to me — I can't think of
pubsub use cases where starting broad would be desired (rss/news
distribution, email subscriptions, chats, market data all imply
explicit subscriptions).

> One way to solve this is with two socket types, each offering a
> specific metaphor, through naming and default behaviour.  But that
> adds complexity.

But you've already got a socket type that performs unidirectional
multicast on the publishing side and aggregation of data from multiple
sources on the other — ZMQ_PUSH/ZMQ_PULL. If you add support for
filtering, it will behave exactly as you've described — initial
“subscription” to everything with potential filtering. That leaves
ZMQ_SUB with the current behavior (with maybe publisher-side filtering
optimizations and support for additional positive/negative filters).