PUB functions the same in 3.1 as 2.1, but XPUB actually does publisher
side filtering. (if I read the code correctly)
Joshua
On 3/13/2012 1:39 PM, Calvin de Vries wrote:
I'm not sure this is correct, Joshua. PUB filters the messages in 3.1,
while you can use XPUB in order to do more advanced subscription
management, it is not a requirement to have publisher side filtering.
In Steve's example, Subscriber A would not receive every message, only
messages matching its filter.
On Mon, Mar 12, 2012 at 7:43 PM, Joshua Foster <[email protected]
<mailto:[email protected]>> wrote:
3.1 works the same way as 2.1 in your example. The changes in 3.1
is that the subscription is forwarded to the PUB socket. This
allows you to create a publisher device. It would sit between the
parent publisher and the subscriber. The XPUB keeps track of the
subscriptions and allows them to apply to the XSUB socket. This
effectively filters out any messages that do not match a
subscription. In your example, you are matching against "a" and ""
so all messages would be passed through.
You can of course use a ROUTER socket and manage the subscriptions
yourself in the application (with DEALER). The main downside is
that you won't be able to detect client disconnections. You may
also want to consider creating an alternative PUB socket
implementation in ZeroMQ.
Joshua
On 3/12/2012 6:48 PM, Steve wrote:
I have a high level question about how a v3.1 publisher handles
sending updates to subscribers. I understand that v3.1 can push
the subscription filtering further towards the publisher but to
what degree I'm unclear on.
Here is a very simple usage example:
1) Publisher has a list of topics that are randomly updated 10
times a second. There are a total of 26 topics and each is a
single lowercase alpha character representing the English
alphabet (a - z).
2) Subscriber 'A' subscribes to just a topic matching "a".
3) Subscriber 'B' subscribes to all topics ("").
In version 2.1, I believe Subscriber 'A' would receive all the
messages and that the zeromq client library would filter them so
the client would only see updates on 'a'. In version 3.1, is it
possible to filter the messages at the publisher so that
Subscriber 'A' only receives updates on topic 'a' (no filtering
done on the client) and that Subscriber 'B' receives all updates
on all topics (a-z)?
Thanks,
Steve
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