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Posted to users@qpid.apache.org by Toralf Lund <to...@pgs.com> on 2011/08/15 13:34:29 UTC
Specify key for LVQ?
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.
- Toralf
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Re: Specify key for LVQ?
Posted by Toralf Lund <to...@pgs.com>.
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).
>
Good.
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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Re: Specify key for LVQ?
Posted by Gordon Sim <gs...@redhat.com>.
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.
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).
---------------------------------------------------------------------
Apache Qpid - AMQP Messaging Implementation
Project: http://qpid.apache.org
Use/Interact: mailto:users-subscribe@qpid.apache.org