[zeromq-dev] Can a pub-sub endpoint have multiple publishers?

[James Renkel]

Pieter,

Thank you for your prompt reply, and I apologize for not having the 
terminology right, but please bear with me, I'm new to this.

Let me rephrase the question:

Is it possible for a subscriber to be connected to multiple publishers 
with a single subscribe request?

Or:

Must a subscriber connect to each publisher separately?

The idea here is that publishers come and go, subscribers come and go, 
but at any time we want all subscribers to be subscribed to all publishers.

We would like to be able to do that as simply as possible by having 
publishers publish to a single "resource" as each starts up, subscribers 
subscribing to that same single resource as each starts up, and having 
all the plumbing taken care of as publishers and subscribers come and go.

I guess the real question then is "Does ZMQ provide something that can 
be used out of the box as that resource? Or is that something we're 
going to have to build?".

If it's something we're going to have to build, it's starting to look 
like a message broker, which needs separate configuration, duplication 
for redundancy, extra message passing, processing, and delay, etc., all 
the things we were hoping to avoid by not having to have a message broker.

If it helps, all of the publishers and subscribers are co-located and 
attached to the same (virtual) LAN segment, so we are looking to use 
some form of reliable multi-cast (PGM, EPGM, NORM) for communication 
between the publishers and subscribers.

Again, thank you in advance for your attention to this.

Jim Renkel
Senior Technical Staff
mFluent, Inc. LLC
mailto:james at mfluent.com

On 14/4/14, 14:57 , Pieter Hintjens wrote:
> Reading the Guide is OK. Actually trying to examples and learning the
> basics is usually better. The answer to your question is, that's not
> quite how it works. You can connect all subscribers to all publishers,
> or you can create proxies in the center, but there is no such thing as
> a "pub sub endpoint" in a ZeroMQ network.
>
> -Pieter
>
> On Mon, Apr 14, 2014 at 7:27 PM, James Renkel <james at mfluent.com> wrote:
>> The communication pattern of our application is best described as a
>> "message bus": all messages sent by any "sender" on the bus are
>> delivered to all "receivers" on the bus.
>>
>> After having read the ZMQ guide, it seems that the "pub-sub" pattern is
>> the closet match to this, if a pub-sub endpoint can have multiple
>> publishers.
>>
>> I couldn't find anything that specifically prohibits this, but I also
>> couldn't find anything that specifically permits this.
>>
>> So the question is really simple: can a pub-sub endpoint have multiple
>> publishers, such that all messages published by any publisher will be
>> delivered to all subscribers?
>>
>> Has this been tried and is it known to work, or are will be be breaking
>> new ground here? We're not opposed to that, we just want to know what
>> we're getting ourselves in for.
>>
>> Thank you in advance for your attention to this.
>>
>> Jim Renkel
>> Senior Technical Staff
>> mFluent, Inc. LLC
>> mailto:james at mfluent.com
>> _______________________________________________
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>> zeromq-dev at lists.zeromq.org
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