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

[Bill Torpey]

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 <https://github.com/nyfix/OZ> which powers https://www.broadridge.com/financial-services/capital-markets/trading-and-connectivity/order-routing-network <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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>>>>> zeromq-dev at lists.zeromq.org
>>>>> https://lists.zeromq.org/mailman/listinfo/zeromq-dev
>>>> 
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