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From Akila Ravihansa Perera <>
Subject Re: [Fixed] CEP sends very large values for gradient and second derivative of load average
Date Thu, 06 Nov 2014 19:17:29 GMT

On Nov 6, 2014 11:37 AM, "Imesh Gunaratne" <> wrote:
> Thanks for your response Nirmal, please see my thoughts below:
> On Thu, Nov 6, 2014 at 7:38 PM, Nirmal Fernando <
> wrote:
>> AFAIU if it is statistics, it's all about random data, samples and
normalization. You don't use all values to do estimations. And this is an
estimation for gradient per say!
> True, however the random data needs to be accurate as much as possible.
>> Well, statistics we are calculating is for a cluster as a whole not
member wise. Since, we autoscale a cluster.
> Yes for autoscaling a cluster the aggregated statistics should be
calculated against the cluster. However I do not think that we can mix each
statistic accorss members when calculating differences. Different members
of a cluster might be running at different resource usage levels at a given
point of time. Therefore aggregation might needed to be done at the member
level first and then on the cluster level. WDYT?


We need to sample stats and aggregate them on fixed intervals before
calculating the gradients.


> --
> Imesh Gunaratne
> Technical Lead, WSO2
> Committer & PMC Member, Apache Stratos

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