[rrd-users] Time Shift on Trend Graph

Chris Mason chris at netnix.org
Tue Jul 2 09:55:21 CEST 2013


Thanks for your response, but I have since stumbled across this post:

I am trying to do the same thing as was discussed in this post (i.e. have
the first function actually return the first point in the RRA with an
actual data value).

In simple terms, I am trying to make my graph grow from the left instead of
the right and I am looking for a <TIME> to pass "rrdtool graph -s <TIME>"
to achieve this.

I am going to look at storing the create time of the RRD and comparing it
with the response from first to see what is the latest value - however, I
would still need to round my create time up to the next RRA interval
otherwise I might have a bit of white space at the beginning.


On 1 July 2013 23:12, Alex van den Bogaerdt <alex at vandenbogaerdt.nl> wrote:

> ----- Original Message -----
> From: "Chris Mason" <chris at netnix.org>
> To: <rrd-users at lists.oetiker.ch>
> Sent: Monday, July 01, 2013 12:27 PM
> Subject: Re: [rrd-users] Time Shift on Trend Graph
> > Hi,
> >
> > I am assuming "rrdtool last" returns the actual last time because when
> you
> > add new data to the RRD, it rotates the RRD and the stuff that was
> > previously at the beginning interval is pushed out - to always maintain
> > the
> > same length and size of an RRD - you are always adding to the end?
> >
> > I am starting to conclude, after getting the feeling that I am talking to
> > myself, that I can't obtain the point in my RRD when I first entered
> data?
> > Would it not be the first non-unknown value in the data source and can I
> > obtain this easily to use this to determine the start time of my graph?
> Never tried it myself, but in the doc I find: rrdfirst Return the date of
> the first data sample in an RRA within an RRD
> And if that does not work, You could try to use a VDEF function for this.
> Not surprisingly you would need "FIRST" again. Print it's time component.
> If these two are not what you're after, then you will need to rephrase your
> problem.
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