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From Jakub Scholz <ja...@scholz.cz>
Subject Re: Any way Qpid could preserve messages in TOPICS. Possibility ?
Date Thu, 15 Aug 2013 12:05:16 GMT
Hi Gordon,

Curious question ... would a message from an exchange configured as
"Initial Value Exchange" get propagated through the topic when a new
subscription is created (assuming the routing key and binding keys are a
match)?

Thanks & Regards
Jakub


On Thu, Aug 15, 2013 at 10:44 AM, Gordon Sim <gsim@redhat.com> wrote:

> On 08/14/2013 07:55 PM, Rajesh Khan wrote:
>
>> It seems like we are running into a requirement and I wanted to know if
>> there was a way for TOPICS to preserve the last message Initially I was
>> using LVQ which was really great however due to acknowledging messages and
>> the delay we get because of that I moved to using QPID topics instead of
>> queues. Now I want to know if there is a way of preserving the last
>> message
>> in a topic or if there is a way of disabling receive acknowledgment in
>> Queues.
>>
>
> The distinction between queue and topic is a slightly fuzzy one. In JMS of
> course they represent two distinct messaging patterns. In pre 1.0 AMQP,
> there is no concept of a 'topic' - generally the topic pattern as
> understood in JMS is implemented by binding a queue per subscription to an
> exchange.
>
> However, another way of getting a similar pattern is  using a queue to
> which subscribers connect as 'browsers' (non-destructive, non-competing
> consumers of the messages). Used in this mode the LVQ is essentially a
> topic that retains the last message for a given key value.
>
> For browsers on a queue, the acknowledgement isn't actually needed in that
> case.
>
> For competing, i.e. destructive consumers, the acknowledgement can be
> implied meaning no explicit acknowledgement needs to be issued. To do this
> you would put 'reliability: unreliable' in your link options in the address
> with which the receiver was created.
>
> I am however curious also as to the delay you were observing. If
> acknowledging every n messages, and doing so asynchronously, I would not
> expect a very large impact on throughput and certainly no 'delay' (as I
> understand the term).
>
>
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