[rrd-users] Newbie question: Always missing the last datapoint in rrdtool graphs
Alex van den Bogaerdt
alex at vandenbogaerdt.nl
Thu Feb 26 15:35:36 CET 2009
----- Original Message -----
From: "Ole Holm Nielsen" <Ole.H.Nielsen at fysik.dtu.dk>
To: "Alex van den Bogaerdt" <alex at vandenbogaerdt.nl>
Cc: <rrd-users at lists.oetiker.ch>
Sent: Thursday, February 26, 2009 3:24 PM
Subject: Re: [rrd-users] Newbie question: Always missing the last
datapoint in rrdtool graphs
> Alex van den Bogaerdt wrote:
>> Updates are describing the past:
>> More info on UTC: http://www.vandenbogaerdt.nl/rrdtool/timezone.php
>> Most people don't look at midnight to midnight local time. They
>> look at midnight to midnight UTC time.
> Thanks a lot for your tutorials and explanation! This is most
> It's beginning to dawn upon me that the RRD databases always use UTC
> The problem I'm seeing is that when I create a database that starts
> Tue 01 Jan 2002 12:00:00 AM CET (New Year in my local timezone):
> # rrdtool create test.rrd --start 1009839600 --step 86400 \
> DS:running:GAUGE:86400:0:U RRA:AVERAGE:0.5:1:3650
> then internally rrdtool doesn't do what I intended, since it seems
> to shift
> the timestamps from 00:00:00 CET to 01:00:00 CET = 00:00:00 UTC:
> # rrdtool dump test.rrd
> <!-- 1992-01-04 01:00:00 CET / 694483200 --> <row><v> NaN
> The quick answer is presumably that this shows rrdtool working as
> However, I do NOT want to look at midnight to midnight UTC time, I
> must look at midnight to midnight local time! The reason for this
> is that our Linux cluster, which operates with the Torque Resource
> (a batch job system), generates daily accounting files in *local
> time*, i.e.,
> for each day in local time a file is created named like "20090226".
Sure. And how many hours are there in such a day?
The answer will be: 363 or 364 times 24 hours, 1 time 23 hours and 1
time 25 hours.
This is not really a problem, as long as you remember this when you do
tricks like multiplying the average rate by the amount of time to get
total bytes transfered.
> So the natural period of time for my system is from 00:00:00 until
> local time, not UTC time (please do not suggest to fix the Torque
> to use UTC!).
What you can do: work using UTC yourself. That's on the page
describing timezones. If you can get 'TZ="UTC" date' working, you can
also get 'TZ="UTC" rrdtool' working.
Update at midnight UTC (I mean: using the timestamp which is midnight
UTC), using the values you want to be in your database.
Then create your graph with: 'TZ="UTC" rrdtool graph ...' in stead of
just 'rrdtool graph ...'
This should work.
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