[zeromq-dev] Adding new zmq_getsockopt() to retrieve number of subscriptions from XPUB socket

[Francesco]

Hi everybody,

A PR implementing this idea (ZMQ_SUBSCRIPTION socket option) is now
available here:
  https://github.com/zeromq/libzmq/pull/4459

Any comment is appreciated,

thanks,
Francesco



Il giorno mer 16 nov 2022 alle ore 16:10 Bill Torpey
<wallstprog at gmail.com> ha scritto:
>
> Hi Francesco:
>
> Just to be clear, I’m not a maintainer, just an interested party.  (At my day job I created https://github.com/nyfix/OZ which powers https://www.broadridge.com/financial-services/capital-markets/trading-and-connectivity/order-routing-network).  I believe that Luca is currently the main person responsible for the repo.
>
> As for your proposed PR, anything that provides more visibility to what is going on “under the hood” with ZeroMQ is A Good Thing, I think.
>
> Regards,
>
> Bill
>
> On Nov 16, 2022, at 6:54 AM, Francesco <francesco.montorsi at gmail.com> wrote:
>
> Hi Bill,
> ok thanks, sure. I can prepare such PR... I just wanted to get a
> feedback from other maintainers... I think PRs are mostly reviewed and
> merged by Luca at this point right?
>
> Luca,
> what do you think about my proposal of new getsockopt to get number of
> actual subscriptions?
> Example usage:
>
> /* Retrieve number of subscriptions */
> int subscriptions;
> size_t subscriptions_size = sizeof (subscriptions);
> rc = zmq_getsockopt (socket, ZMQ_SUBSCRIPTION_COUNT, &subscriptions,
> &subscriptions_size );
>
> // NOTE: ZMQ_SUBSCRIPTION_COUNT would be applicable only to XPUB, PUB,
> XSUB, SUB socket types
>
>
> Thanks,
> Francesco
>
>
> PS: I think it would be nice to have visibility about subscriptions
> added/removed also on the socket monitor... but that's a lot of more
> detailed information... I think the basic use case is just to get the
> whole number of subscriptions (for debugging you often know how many
> subscriptions were sent and it's useful to check if any subscription
> has been dropped for some reason)
>
>
>
> Il giorno mer 16 nov 2022 alle ore 01:32 Bill Torpey
> <wallstprog at gmail.com> ha scritto:
>
>
> Sorry Francesco — I meant your PR, I just mixed up the names.
>
> B.
>
> On Nov 15, 2022, at 5:01 PM, Francesco <francesco.montorsi at gmail.com> wrote:
>
> Hi Bill,
>
> Arnaud’s PR sounds useful — more visibility can only be a good thing.
>
>
> sorry I'm missing which PR you are talking about... is there an
> existing PR to add more visibility (I'd love that)? Or you're
> referring to the proposal I did in my first mail?
>
> thanks,
> Francesco
>
> Il giorno mar 15 nov 2022 alle ore 22:58 Bill Torpey
> <wallstprog at gmail.com> ha scritto:
>
>
> The problem with all the socket monitor stuff is that it’s async — that makes it dangerous to act on.  It’s great for monitoring/debugging -- for real-time control not so much.
>
> Arnaud’s PR sounds useful — more visibility can only be a good thing.
>
> Bill
>
> On Nov 15, 2022, at 10:43 AM, Arnaud Loonstra <arnaud at sphaero.org> wrote:
>
> On 15-11-2022 15:57, Francesco wrote:
>
> Hi zeromq team,
> For "observability" / debugging I think it would be really really
> useful to be able to retrieve the number of subscriptions recorded by
> the 'mtrie_t' object inside a (X)PUB socket.
> Would you accept a PR adding such option?
> Thanks,
> Francesco
>
>
> Isn't that possible through the socket monitor?
>
> http://api.zeromq.org/4-1:zmq-socket-monitor
>
> Rg,
>
> Arnaud
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