[zeromq-dev] Behavior of Labels, Identities, and Socket Types in 3.0

[Gregory Szorc]

On 10/26/11 12:37 PM, MinRK wrote:
> Here's a script with pyzmq that runs various combinations of sockets,
> and a side-by-side diff comparing the behaviour when run with 2.1.10 vs
> 3.0.2:
>
> https://gist.github.com/1317498
>
> Should be trivial to add more socket combinations.

Great work!

I immediately noticed an inconsistency between the results and the docs.

 From zmq_socket:

> When a 'ZMQ_REQ' socket is connected to a 'ZMQ_ROUTER' socket, in addition to the
> _identity_ of the originating peer each message received shall contain an empty
> _delimiter_ message part. Hence, the entire structure of each received message
> as seen by the application becomes: one or more _identity_ (label) parts, an
> empty _delimiter_ part, and one or more _data parts_.

 From your 3.0 output:

> Testing REQ -> ROUTER
>   REQ sending 'hi': ok
>   ROUTER receiving: ['REQ', 'O\xce\xb5\xee', 'hi']

No empty message :(

I noticed a commit in 3.0 today that seems to touch code at the heart of 
this thread: 
https://github.com/zeromq/zeromq3-0/commit/5c42a8aa3bc3a914e00223e12340443a1443c541. 
I haven't tested that commit yet. Maybe it makes the code consistent 
with the docs?

Anyway, I fixed my application by changing all the DEALER and ROUTER 
sockets (back to) XREQ and XREP. Like I said in my initial post, I 
prefer 3.0's explicit label model rather than the empty message 
convention of 2.x. Still, I'd like some (official) feedback on expected 
behavior and best practices for 3.0.

Greg