[zeromq-dev] XPUB subscription notifications

[Pieter Hintjens]

Dan,

I've gone and added ZMQ_XPUB_VERBOSE (pull request waiting, commit is
at https://github.com/hintjens/libzmq/commit/f87bf3).

It was quite simple. Not sure if you are able to test this but that'd be nice.

-Pieter



On Sat, Oct 6, 2012 at 1:05 AM, Dan Goes <DGoes at blueorigin.com> wrote:
> Thanks for all the ideas, I'll look into implementing one of these. Given our design, and that connection awareness on the publisher side is primarily a diagnostic feature, something like Pieter's setsockopt solution would be ideal due to its simplicity (if less robust to the things that Ian mentioned). But, our requirements may change and necessitate an explicit protocol.
>
> Dan
>
> -----Original Message-----
> From: zeromq-dev-bounces at lists.zeromq.org [mailto:zeromq-dev-bounces at lists.zeromq.org] On Behalf Of Ian Barber
> Sent: Friday, October 05, 2012 3:27 AM
> To: ZeroMQ development list
> Subject: Re: [zeromq-dev] XPUB subscription notifications
>
> On Thu, Oct 4, 2012 at 7:25 PM, Pieter Hintjens <ph at imatix.com> wrote:
>>
>> I can see two options. One is to extend XPUB so it does this, enabling
>> that with a setsockopt. Second is to switch to ROUTER sockets with an
>> explicit protocol for subscription and last used values.
>>
>> -Pieter
>
> +1 - the idea with the PUB/SUB implementation is that you are dealing
> with a group, whos membership may change without affecting the publisher (particularly for trees of pubs). You could use a subscribe message in a specific format (like sub-IP-port) or similar to ensure you're triggered an XPUB message upstream, but unless you have return channel heartbeating as well, you're not going to be aware of timeouts, disconnects, reconnects and so on, particularly > 1-hop down. If that stuff is what you need, build the protocol over ROUTER.
> It's worth thinking through the error cases though and seeing whether you could use, say, PUB/SUB with a sequence number and a separate repairer to handle dropouts, which makes life easier in some cases.
>
> Ian
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