[zeromq-dev] XPUB subscription notifications

Ian Barber ian.barber at gmail.com
Fri Oct 5 12:27:26 CEST 2012


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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