[rrd-users] Re: Current (LAST) samples always show 0 in legend

Alex van den Bogaerdt alex at ergens.op.het.net
Sun Apr 13 13:29:36 MEST 2003

On Sat, Apr 12, 2003 at 01:32:50PM -0400, Bill Sandiford wrote:
> I have recently installed rrdtool and 14all to work with my install of mrtg 2.9.28.  Everything appears to be working fine with the
> exception of the current in/OUT value in the legend of the graph...It always displays 0.
> Someone had given me the following suggestion but it didn't seem to work (in fact when I did this I got a big red image that said
> CANNOT CREATE GRAPH)..they had suggested that the problem was because either rrdtool or 14all.cgi didn't know what 'now' meant

I think that ("didn't know what 'now' meant) is somewhat inaccurate ...

> >Open 14all.cgi and find the following :
> >my %graphparams = (
> >         'daily'   => ['-2000m', 'now',  300],
> >        'weekly'  => ['-12000m','now', 1800],
> >         'monthly' => ['-800h', 'now',  7200],
> >         'yearly'  => ['-400d', 'now', 86400],
> >         'daily.s' => ['-1250m', 'now',  300],
> >);
> >
> >and change it to
> >
> >my %graphparams = (
> >         'daily'   => ['-2000m', '-5m',  300],
> >        'weekly'  => ['-12000m','-30m', 1800],
> >         'monthly' => ['-800h', '-2h',  7200],
> >         'yearly'  => ['-400d', '-1d', 86400],
> >         'daily.s' => ['-1250m', '-5m',  300],
> >);

I don't know 14all.cgi that well, but I think it is safe to say what
the intention is:

This is an attempt to skip the last row in an RRA, the one not yet being

What happens:

If you query the database for "--end now" "--start end-2000m", you are
asking RRDtool to return the 2000 minutes ending "now".

Currently it is 11:26 UTC.  "now" is 11:26 UTC.  RRDtool must therefore
include the interval covering 11:26 UTC.  This interval starts at 11:25
and ends at 11:30.  The interval from 11:25 to 11:30 has not yet been
completed and thus has "NaN" (or: Unknown) as its rate.  I guess 14all
changes this into 0.

There may be another possible reason why "current" always displays 0
but as I said: I don't know 14all.cgi

If above patch doesn't work, it may be that the resulting command line
looks weird.  Try "now-5m" in stead of just "-5m" and so on.

Much of what looks like rudeness in hacker circles is not intended to give
offence. Rather, it's the product of the direct, cut-through-the-bullshit
communications style that is natural to people who are more concerned about
solving problems than making others feel warm and fuzzy.


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