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From Antony Blakey <>
Subject Re: Statistics Module
Date Fri, 30 Jan 2009 06:58:41 GMT

On 30/01/2009, at 4:27 PM, Paul Davis wrote:

> On Fri, Jan 30, 2009 at 12:32 AM, Antony Blakey < 
> > wrote:
>> On 30/01/2009, at 9:56 AM, Paul Davis wrote:
>>> The way that stats are calculated currently with the dependent
>>> variable being time could cause some issues in implementing more
>>> statistics. With my extremely limited knowledge of stats I think
>>> moving that to be dependent on the number of requests might be  
>>> better.
>>> This is something that hopefully someone out there knows more about.
>>> (This is in terms of "avg for last 5 minutes" vs "avg for last 100
>>> requests", (the later of the two making stddev type stats
>>> calculateable on the fly in constant memory.)
>> The problem with using # of requests is that depending on your  
>> data, each
>> request may take a long time. I have this problem at the moment: 1008
>> documents in a 3.5G media database. During a compact, the status in
>> _active_tasks updates every 1000 documents, so you can imagine how  
>> useful
>> that is :/ I thought it had hung (and neither the beam.smp CPU time  
>> nor the
>> IO requests were a good indicator). I spent some time chasing this  
>> down as a
>> bug before realising the problems was in the status granularity!
> Actually I don't think that affects my question at all. It may change
> how we report things though. As in, it may be important to be able to
> report things that are not single increment/decrement conditions but
> instead allow for adding arbitrary floating point numbers to the
> number of recorded data points.

I think I have the wrong end of the stick here - my problem was with  
the granularity of updates, not with the basis of calculation.

Antony Blakey
CTO, Linkuistics Pty Ltd
Ph: 0438 840 787

It is no measure of health to be well adjusted to a profoundly sick  
   -- Jiddu Krishnamurti

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