[zeromq-dev] Any way to get info on subscribers?

[Brian Granger]

On Sat, Jul 24, 2010 at 7:38 AM, Martin Sustrik <sustrik at 250bpm.com> wrote:

> Pieter,
>
> >> This info is in principle not available. 0MQ abstracts from the notion
> >> of individual connections. All you have is an opaque cloud of peers.
> >
> > Does that cloud have to be opaque by definition?  For example, the
> > publisher socket knows how many clients have connected to it, and
> > could report this to the application via getsocketopt...
>
> My rationale for hiding the info is that the semantics are not
> consistent across different topologies:
>
> 1. In direct PUB/SUB over TCP you get number of consuming apps.
> 2. With PUB/SUB over multicast you get no sane value.
> 3. With TCP and a device(s) in the middle you'll get more or less random
> number that has nothing to do with number of subscribing apps.
>
>
What about using 0MQ identities for this?  They are uniform across
transports and can propagate across devices.
It seems like identities are the main abstraction in 0MQ for a remote
endpoint.



> >> All in all, if you need to handle individual connections manually, you
> >> should go for standard sockets rather than 0MQ.
> >
> > 0MQ sockets do several useful things above TCP sockets:
> >
> > * transport abstraction
> > * message queuing
> > * message bundling
> > * automatic reconnection
> > * message framing incl. multipart
> > * routing patterns
> >
> > Using TCP sockets forces one to recreate all this work, which is
> > pretty horrid.  If one wants to use a custom routing pattern (e.g. to
> > do content based routing), then 0MQ might offer "raw" sockets that do
> > all the work except the routing, and allow the application to do that.
> >  It still adds significant value over TCP.
>
> Can be done. Of course, it means splitting the 0MQ codebase into two
> parts, meaning a *lot* of both design and implementation work.
>
> Martin
>
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>



-- 
Brian E. Granger, Ph.D.
Assistant Professor of Physics
Cal Poly State University, San Luis Obispo
bgranger at calpoly.edu
ellisonbg at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.zeromq.org/pipermail/zeromq-dev/attachments/20100724/e66f4044/attachment.htm>