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From Gordon Sim <g...@redhat.com>
Subject Re: Why performance of sending durable messages to qpid queue is really bad?
Date Wed, 18 Jun 2014 20:25:19 GMT
On 06/18/2014 06:39 PM, Fraser Adams wrote:
> On 18/06/14 09:13, Gordon Sim wrote:
>> On 06/17/2014 10:35 PM, smartdog wrote:
>>> It is the qpid c++ broker. The BDB store is used. Is there a way to
>>> improve
>>> the performance while preserving the persistence?
>>
>> Can you send messages in batches? I.e. don't make every send synchronous.
>>
>> A synchronous send will always be a little slower and for the c++
>> broker if the message is durable there is an added penalty at present
>> over AMQP 1.0 as the broker doesn't flush the disk immediately (it
>> doesn't get any explicit indication that the client is not going to
>> send anything else until it gets back the disposition for the message).
>>
>>
> Pavel & Gordon, smartdog's original comment said "sending an undurable
> message to a qpid queue takes 1-3ms, while sending a durable message
> takes static 1000ms" taking 1 second does seem awfully high even given
> the synchronous and flush comments, clearly the message size may be
> significant, but I'm guessing if he was sending *really big* messages
> he'd have said so it's probably not significant here, so the flush delay
> seems plausible.
>
> what determines when the flush occurs?

Over 0-10, the client can explicitly trigger the flush by sending a sync 
control (or setting the sync flag on the transfer). There is no such 
explicit mechanism in 1.0, so at present the flush happens after a short 
timeout on the broker side.

This was discussed in a thread started by Pavel some weeks ago. The 
broker would need to be altered to allow it to recognise that a given 
message is not part of a batch (e.g. because there is no further data 
and no further messages for that queue in the data received). This isn't 
a trivial change unfortunately.


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