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From Paul Davis <>
Subject Re: Statistics Module
Date Fri, 30 Jan 2009 07:02:36 GMT
On Fri, Jan 30, 2009 at 1:58 AM, Antony Blakey <> wrote:
> 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.

Heh. Well, we can only measure what we know. And in the interest of
simplicity I think the granularity is gonna have to stick to pretty
much per request. Also you're flying with 300 MiB docs? perhaps its
time to chop or store in FTP?

> Antony Blakey
> -------------
> CTO, Linkuistics Pty Ltd
> Ph: 0438 840 787
> It is no measure of health to be well adjusted to a profoundly sick society.
>  -- Jiddu Krishnamurti

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