stratos-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Nirmal Fernando (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (STRATOS-939) CEP sends very large values for gradient and second derivative of load average
Date Wed, 05 Nov 2014 20:35:35 GMT

     [ https://issues.apache.org/jira/browse/STRATOS-939?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Nirmal Fernando updated STRATOS-939:
------------------------------------
    Attachment: STRATOS-939.diff

> CEP sends very large values for gradient and second derivative of load average
> ------------------------------------------------------------------------------
>
>                 Key: STRATOS-939
>                 URL: https://issues.apache.org/jira/browse/STRATOS-939
>             Project: Stratos
>          Issue Type: Bug
>          Components: CEP
>    Affects Versions: 4.1.0 M3
>            Reporter: Nirmal Fernando
>            Assignee: Nirmal Fernando
>            Priority: Critical
>             Fix For: 4.1.0 M4
>
>         Attachments: STRATOS-939.diff
>
>
> How we calculate gradient of two events? 
> Say the events are; e1(t1,v1) and e2(t2,v2) 
> tx - time in milliseconds when xth event occurred
> vx - value (memory, cpu etc.) that xth event carries
> time gap = t(2-1) = t2 -t1 milliseconds
> time gap in seconds = t(2-1) = (t2 - t1)/1000 seconds
> Hence,
> Gradient = (v2 - v1)  / t(2-1)  = ( (v2 - v1) * 1000 ) / (t2 - t1)
> I've enabled debug logs for CEP extension;
> log4j.logger.org.apache.stratos.cep.extension=DEBUG
> Please find the following 3 logs extracted from the debug logs;
> ===================================================================
> TID: [0] [STRATOS] [2014-11-05 19:47:27,073] DEBUG {org.apache.stratos.cep.extension.SecondDerivativeFinderWindowProcessor}
-  Gradient: -0.1996007984031936 Last val: 9.0 First val: 12.0 Time Gap: 15030 t1: 1415213202095
t2: 1415213217125 hash: 155426542
> TID: [0] [STRATOS] [2014-11-05 19:47:27,073] DEBUG {org.apache.stratos.cep.extension.SecondDerivativeFinderWindowProcessor}
-  Gradient: -999.9999999999998 Last val: 7.000000000000001 First val: 12.0 Time Gap: 5 t1:
1415213232152 t2: 1415213232157 hash: 155426542
> TID: [0] [STRATOS] [2014-11-05 19:47:27,074] DEBUG {org.apache.stratos.cep.extension.SecondDerivativeFinderWindowProcessor}
-  Gradient: -44.34884666437174 Last val: -999.9999999999998 First val: -0.1996007984031936
Time Gap: 22544 t1: 1415213209610 t2: 1415213232154 hash: 155426542
> ===================================================================
> So, as you can see the reason behind a large value is when the time gap between two subjected
events is less than 1 second. This could happen since events are coming from different asynchronous
agents and also when there are less number of events.
> FIX
> ====
> So, the fix I propose is a very simple one and it will not compromise anything AFAIS.
> Fix is to calculate time gap as follows;
>                                                        
>                                                       
> time gap = t(2-1) } t2 -t1 > 1000  -----> t2 - t1
>                               t2 - t1 <= 1000 ----> 1000
> I have tested this and works fine.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message