[zeromq-dev] Publisher side filtering

Martin Sustrik sustrik at 250bpm.com
Sat Jan 15 13:07:45 CET 2011


Hi all,

I've applied the publisher-side-filtering-related patches to the 
sub-forward branch on github:

https://github.com/zeromq/zeromq2/tree/sub-forward

The subscriptions are forwarded up the distribution tree till they reach 
the ultimate publisher. The publisher does nothing with the subscription 
at the moment, it just prints out a message about getting the 
subscription. The next step will be to start actually filtering the 
messages.

Anyway. Those of you who want to help with the ongoing work, please to 
try to use the branch and check out whether subscriptions are correctly 
distributed to publishers in different topologies, when re-connections 
happen, when individual nodes fail and are restarted etc.

I'm attaching a simple publisher-device-subscriber test, that seems to work.

Note: Subscription forwarding works a bit different when compared to 
classic broker-style messaging. When there's a forwarder device in the 
middle (broker) with many publishers and subscribers connected 
(clients), the subscriptions are forwarded all the way up to the 
publishers. That's different from standard model when the subscription 
is sent to the broker and the filtering goes on there.

In other words, with standard model, if message that nobody wants is 
sent, it goes to the broker, where it is dropped. With 0mq subscription 
forwarding the message is dropped immediately on the publisher and 
doesn't cross the network at all.

Martin
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