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From Toralf Lund <toralf.l...@pgs.com>
Subject Re: Specify key for LVQ?
Date Mon, 15 Aug 2011 12:52:48 GMT
Gordon Sim wrote:
> On 08/15/2011 12:34 PM, Toralf Lund wrote:
>> I'm looking into the LVQ behaviour for QPid messaging setup. The typical
>> example usage example (in C++) for this is something like:
>> Message request;
>> std::string key;
>> args.getLVQKey(key);
>> request.getHeaders().setString(key, "key1");
>> request.setData("something");
>> ...
>> That's all very well for some uses, I suppose, but where does the key
>> actually come from? I can't find a way to set it via the C++ APIs, or by
>> using something like qpid-config. So, is the "LVQ key" some magic
>> property set internally? Isn't it supposed to be possible request "LVQ
>> behaviour" for any key according to AMQP?
>> I think (in my application) I would prefer not having the sender set an
>> "LVQ key" as such, but instead just set one or more general "id"
>> properties, and let messaging config external to the application decide
>> if a queue is an LVQ, and if it is, which property to use when deciding
>> if messages are to be considered the same.
> You can specify the property to use as the key when creating the queue 
> by naming it as the value for 'qpid.last_value_queue_key' in the 
> arguments to the declare.
OK. Thanks.
> This was first available from the 0.10 release in the c++ broker, and is 
> now the only argument needed to enable LVQ behaviour. Prior to that the 
> broker hardcoded this to 'qpid.LVQ_key'. The 0.10 release also made the 
> previous modes irrelevant (you no longer have to choose between 
> intuitive behaviour for browsers and correct consolidation of queue state).

I suppose it's about time to switch to 0.10, then. I have mostly used 
0.8 so far...

- Toralf

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