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Subject: Re: Journal with LVQ
From: Kim van der Riet <kim.vdriet@redhat.com>
To: users@qpid.apache.org
Cc: Gordon Sim <gsim@redhat.com>
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Organization: Red Hat
Date: Tue, 15 Feb 2011 10:31:49 -0500
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On Tue, 2011-02-15 at 09:08 -0500, Alan Conway wrote:
> >> I was asking if there is a way to know the used size of the journal
> in a
> >> given time. When I run my publisher for the first time, and in
> qpid-stat
> >> the queue size 2m in bytes, how can I know the effectively used
> journal?
> >
> > The calculation is quite complex and there tend to be lots of
> variables (exact
> > timings of dequeues v. enqueues, relative messages sizes etc). in
> practical
> > terms I have not found a way to accurately estimate the journal size
> required
> > and so always greatly inflate it. It is an area I think we need to
> make simpler
> > in some way.
> >
> 
> Perhaps it would be useful to add some management instrumentation to
> the 
> journals, so it is at least easy to see how much space is actually
> used when you 
> run a test (or indeed in production so you can see if you're getting
> close to 
> the limit)
> 
This has been discussed. It is likely that a QMF function call would be
added which would calculate the amount of space left in the store when
it is called. However, to do this continually (it through
instrumentation) would likely be expensive and could slow the store down
significantly.

That said, we want to make this accessible and are looking for smart
ways to do it.


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