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From Rajesh Khan <rajeshkhan...@gmail.com>
Subject Re: Getting "[Broker] warning Exception on notification of dequeue" What does this mean ?
Date Fri, 01 Feb 2013 13:13:11 GMT
Hi Gordon , thank you for your reply. Here is the result of qpid-config for
the specific queue
LVQChart-5Min-2   --max-queue-size=0
--max-queue-count=0 --limit-policy=ring --lvq-key=Symbol*

It seems that the queue size did get passed.Also let me explain my scenario
a little more in detail maybe that might help.
I currently have a sender(C++) and a receiver(C#). The sender sends about
30-40 messages in a millisecond. I have set the capacity of the sender to
40,000 and the receiver capacity to 0. The receiver also sends back
acknowledgment after 30,000 messages.The reason for having a 0 at the
receiver side is because the queue is a LVQ type and I always want the
latest value from it setting a capacity gets previous values so I have set
a 0 in order to prevent collecting messages at the receiving side for now i
do not mind the round trips.Anyways with this configuration both the sender
and receiver worked very well for a while (however I did realize from the
task manager that the memory consumption of Qpid broker got upto 9 GB after
that I started receiving this warning for every message that the sender
sent.Also the transmitter got out of synch with the receiver.This means
that the transmitter stopped transmitting but the receiver was still
receiving messages from the broker.Also I noticed after all the messages
had been read (as I assume since the broker console just stopped displaying
the messages). The memory 9GB did not go down.It only went down altogether
when i stopped my C# receiver and started it again (the receiver started
reading messages Instantly when it reconnected to the broker). I am still
not sure what happened here. Why did I have to restart my C# receiver.No
exceptions were logged from the receiver or the sender side.I dont really
understand this behavior any suggestions on what might be going on. Here
are my questions
1-The memory 9GB did not go down.It only went down altogether when I
stopped my C# receiver and started it again (the receiver started reading
messages Instantly when it reconnected to the broker)*
One theory I have regarding this behavior is that after I started getting
that exception (when things got out of syn (i.e) the receiver wasn't
displaying the latest value) is that the broker wasn't sending messages to
the receiver.And when the receiver disconnected and reconnected it
retrieved all the read messages and memory of the broker went down
altogether. If this theory is correct then why was the receiver still
updating (although out of sync)  messages it had receiver from the broker
after that exception showed up.I would appreciate it if someone could
explain this behavior too.

For now my aim is not to get this exception message. It seems setting the
queue size to 0 isn't helping. Any suggestions/ideas would definitely be
appreciated and welcomed

On Fri, Feb 1, 2013 at 1:59 AM, Gordon Sim <gsim@redhat.com> wrote:

> On 01/31/2013 06:39 PM, Rajesh Khan wrote:
>> Gordon , any suggestion what might be causing this warning exception ?
> It comes from some internal error around the tracking of the aggregate
> queue size. When a message is enqueued the size is incremented, when the
> message is dequeued the size is decremented. This error indicates and
> attempt to dequeue more data than it was actually aware of, which means
> something internally is broken.
>  This exception shows up in the broker after an hour of running my
>> application.
>> I did try setting up a queu with max size = 0 using the following command
>> *python qpid-config add queue LVQTest-5Min-3 --argument
>> qpid.last_value_queue_key=**MChartSymbol --max-queue-size=0*
> If there is no maximum size then you couldn't get the same message as the
> size counter would not be tracked. Perhaps the setting didn't get passed
> through correctly... Does qpid-config queues echo the correct settings back
> to you?
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