Cacti update imprecise value to RRD file

[HongHa]

Dear all,

I have a small issue about the value that Cacti 0.88a(Windows server 2003) display in graph.

Below is an example that I got: I set the threshold below the normal value so cacti will send an email alert.
- Polled value is 703
- Rrdtool update value 703 to RRD file (However this is not the value that was written to RRD file)
- Value in Alert thold mail breach high threshold is 703
- Current value in attached graph in alert mail is 699

=> I think that rrdtool update imprecise value to RRD file. May be CF LAST have problem

Below is the detail information, please have a look and if you know this issue show me how to fix this. Thank you so much.

Clog
Poller result data

Update data to RRD file


Thold Email Alert (Thold 0.4.9)
(I modified to make thold send Hourly (1 Minute Average) graph with alert email)
Subject: ALERT: Site Zoota - HTTP Reponse LWP 4 [time] went above threshold of 100 with 703
Sent: Thu 18-Oct-12 10:05 AM
An alert has been issued that requires your attention.
Host: Site Zoota (zoota.vn)
URL: http://10.151.89.237/cacti//graph.php?l ... 3&rra_id=1
Message: ALERT: Site Zoota - HTTP Reponse LWP 4 [time] went above threshold of 100 with 703


Data from Graph_Xport.php
Title:,""Site - HTTP(S) Response Time""
Vertical Label:,""""
Start Date:,"2012-10-18 06:07:00"
End Date:,"2012-10-18 10:06:00"
Step:,"60"
Total Rows:,"240"
Graph ID:,"263"
Host ID:,"47"

Date,"Code 2xx","Code 3xx","Code 4xx","Code 5xx","No Resp.","Unreach.","Resp.Time","Resp.Rate"
2012-10-18 10:04:00,"5.9195202500e+002","NaN","NaN","NaN","0.0000000000e+000","NaN","5.9195202500e+002","-3.6772812500e+001"
2012-10-18 10:05:00,"6.9908333333e+002","NaN","NaN","NaN","0.0000000000e+000","NaN","6.9908333333e+002","-2.7166666667e+001"
2012-10-18 10:06:00,"7.1675000000e+002","NaN","NaN","NaN","0.0000000000e+000","NaN","7.1675000000e+002","-2.7000000000e+001"

Graph template


RRA Consolidation Functions


Technical Support Data


Please show me what is wrong with my cacti and how to fix this.
Thank you so much.
HongHa

[BSOD2600]

This is how rrdtool functions.

read about consolidation and other features of rrdtool - http://docs.cacti.net/manual:088:8_rrdt ... solidation

[HongHa]

Dear BSOD2600,

Thank for replying.

You said that it is how rrdtool functions, but in site http://oss.oetiker.ch said that:

"When data is entered into an RRD, it is first fit into time slots of the length defined with the -s option, thus becoming a primary data point.
The data is also processed with the consolidation function (CF) of the archive. There are several consolidation functions that consolidate primary data points via an aggregate function: AVERAGE, MIN, MAX, LAST.
AVERAGE the average of the data points is stored.
MIN the smallest of the data points is stored.
MAX the largest of the data points is stored.
LAST the last data points is used."

I also chose all four consolidation function (AVERAGE, MIN, MAX, LAST) for each RRAs: Hourly (1 Minute Average), Daily (5 Minute Average), Weekly (30 Minute Average), Monthly (2 Hour Average), Yearly (1 Day Average)

After that I created graph. However, the current value in graph do not match with the polled value, and the LAST value (from rrdtool.exe xport) do not match with polled value too.

It's mean that the Cacti RRA CF LAST does not work ?
Or Cacti CF LAST work correctly and there is NO WAY to store the precise value into RRD file or to display precise current value in graph due to RRDtool?

I'm looking forward to hearing from you.

Regards/HongHa

[BSOD2600]

possibly these links will shed more info on this issue:

http://docs.cacti.net/manual:088:8_rrdt ... lues_shown
http://www.vandenbogaerdt.nl/rrdtool/process.php
http://www.vandenbogaerdt.nl/rrdtool/after_the_fact.php

If you believe there is still an error, please post the relevant rrdtool commands you used to validate the update/graph logic is broken.