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From Ted Ross <tr...@redhat.com>
Subject Re: Federation & message reliability
Date Mon, 14 Sep 2009 20:41:22 GMT
Rob Springer wrote:
> All - we are considering using federation to ease
> some of the load on our broker, but before starting that work, we had 
> a few questions about how message reliability intersects with 
> federation.  We lean heavily on ACCEPT_MODE_EXPLICIT to ensure 
> reliability in case of a fault in our applications, and so losing 
> reliability in favor of scalability isn't a win for us.  So...our 
> questions:
>  - Does using federated exchanges change the semantics of message 
> transfer (if the link and any relevant queues are durable, etc.)?
>  - In case of Qpid termination, will the BDB store recover in a 
> federated environment just as in a non-federated one?
>
> In general, I suppose our questions can be summed up as "Do the steps 
> or techniques required for reliable (and acknowledged) message 
> transfer change in any way when using federation?"
>
> Thanks, everyone!
> -Rob
>
> ---------------------------------------------------------------------
> Apache Qpid - AMQP Messaging Implementation
> Project:      http://qpid.apache.org
> Use/Interact: mailto:users-subscribe@qpid.apache.org
>
Hi Rob,

Qpid broker federation uses normal AMQP message transfer semantics for 
inter-broker communication.  When setting up a queue route (i.e. 
configuring one broker to consume messages from a specific queue on 
another broker) using the "qpid-route queue add <dest-broker> 
<src-broker> <exchange> <queue>" command, there is a command line option

called "--ack" which controls the way messages are transferred between 
the brokers.  If --ack is not supplied, the inter-broker subscription 
uses accept-mode:none.  If an ack value is supplied, the subscription 
uses accept-mode:explicit and acknowledgements are sent every N messages 
where N is the number supplied in the --ack option.

If the queues in question are durable and the federation route is 
durable, the federated set of brokers should recover cleanly after the 
restart of one, several, or all of the brokers.

-Ted


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