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From <Laurent.Deco...@sungard.com>
Subject RE: java no-auth
Date Wed, 22 Aug 2012 15:02:07 GMT
Rob,

I had a feedback from our technical director, he clarified the rationale behind the sequence.
To understand this fully, you have to consider that our architecture also involves a data
cache. It's like an object oriented database which serves data to client processes. The data
cache also registers to the message broker, so it is also notified when some data are being
changed by a client. Therefore, when client request new data to the data cache, it is guaranteed
to have the freshest set of data. Now you should be able to understand this:

"We require each message to have a unique in-order sequence number assigned by the broker
because this is used to synchronise the messages with the cache when the client requests data
- so for example if the cache is slightly behind then the data request will pause until the
cache has processed up to the same sequence number as the client - this prevents data being
lost when the client requests it from the cache."

-----Original Message-----
From: Rob Godfrey [mailto:rob.j.godfrey@gmail.com] 
Sent: 22 August 2012 16:44
To: users@qpid.apache.org
Subject: Re: java no-auth

OK - ensuring all bound queues receive messages in the same order is a sensible policy option
- though adding a sequence number seems slightly orthogonal to that.  As you suggest the other
alternative there is for a single queue implementation of "topic" - I actually have one of
those for the Java Broker that I did as part of the AMQP
1.0 work.

-- Rob

On 22 August 2012 16:30, Gordon Sim <gsim@redhat.com> wrote:
> On 08/22/2012 03:15 PM, Rob Godfrey wrote:
>>
>> I looked at this
>> briefly before but couldn't really understand a use case where this 
>> feature would be useful.
>>
>> Are you looking for the broker to identify a total ordering over all 
>> messages going through an exchange? Do you need an incrementing 
>> integer?
>
>
> The feature on the c++ broker was for a totally ordered sequence of 
> all messages through the exchange. The pre-1.0 AMQP model is not ideal 
> for pub-sub where you want all subscribers to receive events in the same order.
> That extension to the exchange was a way of working around it where 
> absolutely needed.
>
> I think actually a modified browsable queue would be a better 
> approach, where messages were deleted after being seen by all browsers.
>
>
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