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From Kim van der Riet <kim.vdr...@redhat.com>
Subject Re: journal status before the Enqueue threshold exception ?
Date Wed, 19 Jan 2011 12:36:57 GMT
On Tue, 2011-01-18 at 23:08 -0800, lajithpm wrote:
> hai,
> 
> i am working on linux c++ qpid base and i want to know
> 
> is it possible to determine the journal status before the exception:"Enqueue
> capacity threshold exceeded on queue"... ?
> is it possible to determine the the journal file boundary region ? so that i
> can bypass the "Enqueue capacity threshold" exception.
> 
> 
The short answer is "no", at least not a direct "xx% full" measure or a
current file measure. However, you can get some idea of the state
indirectly through the use of qpid tools or qmf.

Take a look at the following thread (if you have not already seen it),
which contains a detailed explanation on how the enqueue threshold
works.

http://apache-qpid-users.2158936.n2.nabble.com/how-to-resolve-Enqueue-capacity-threshold-exceeded-error-td2626671.html

If you can use qmf/qpid tools to read the queue depth, then you will
have some information you can use to approximate how full the journal
is. This assumes, however, that:
* you are consuming messages in approximately the same order you are
sending them
* that you are not browsing messages (which can keep a message on the
store without allowing it to be dequeued for extended periods)
* that you are not using transactions, which can add enormous overhead
to the store depending on the number of enqueue/dequeue ops are placed
in each transaction.
If any of the above is true, then the ability to estimate based solely
on queue depth is compromised.

The store itself also can be queried through qmf and keeps running
totals of enqueued messages, but there is no measure of %full. This is a
somewhat expensive and complex operation, and it was decided not to
increase the overheads of management by including this for ongoing qmf
operations. I plan to revisit this issue in the near future, however,
and see if there is some way to do this without incurring too large an
overhead.

Hope that helps,
Kim


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