[zeromq-dev] Last Image Caching

Pieter Hintjens ph at imatix.com
Mon Nov 1 18:57:09 CET 2010


Hi Shekhar,

There is no published functionality that does this, as far as I know.

There's been discussion of how to build this using 0MQ.  The general
solution is to maintain state in the publisher, and request this in
the subscriber via a second connection (req/rep).  You'd then apply
incoming pub/sub messages to this data asynchronously.  The key part
is to queue incoming pub/sub data until you've received the cache
snapshot.  In effect, a distributed cache.

ActiveMQ can do it differently because it does not attempt to support
scaling via devices or multicast.  Using multicast, for example, there
is no way for a publisher to know when a subscriber joins, so no way
for it to send the last value for that topic key.

If you are coming to 0MQ from ActiveMQ I'd suggest you read the 0MQ
Guide. 0MQ is really more a toolbox of reusable messaging components
that you can combine in many ways, rather than a pre-built messaging
package like ActiveMQ.

Regards
--
Pieter Hintjens
iMatix


On Mon, Nov 1, 2010 at 6:36 PM, Shekhar Gupta <shekhardk at gmail.com> wrote:
> Hi....Can somebody please help me on how to implement last image
> caching while keeping messages ordered correctly.
> http://activemq.apache.org/subscription-recovery-policy.html
>
> Thank you.
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>
>



-- 
-
Pieter Hintjens
iMatix - www.imatix.com



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