[rrd-developers] Re: RRDs::fetch zero values returns NaN

[Tobias Oetiker]

Today steve rader wrote:

 |
 |  > From: me
 |  > The problem is that NaN values fetched with RRDs::fetch are now
 |  > returned as 'undef' instead of the string 'NaN'.
 |
 | Now I find that RRDs::fetch is broke with respect to zero values:
 | with 1.0.33, RRDs::fetch of zero values returns 'undef'.
 |
 | I wrote a little script to demonstrate the problem... and here's
 | the results...
 |
 |  chive(rader): rrdtool fetch -s -10min -e now \
 |    /usr/local/nrg/web/apache/Chive/Chive-tp.rrd AVERAGE \
 |    | tail -4
 |  984673800: 1.1650888889e+00
 |  984674100: 0.0000000000e+00
 |  984674400: 0.0000000000e+00
 |  984674700:        NaN
 |
 |  chive(rader): ./rrdfetch.pl \
 |    /usr/local/nrg/web/apache/Chive/Chive-tp.rrd AVERAGE \
 |    | tail -4
 |  984673800: 1.1650888889e+00
 |  984674100: 0.0000000000e+00  (undef)
 |  984674400: 0.0000000000e+00  (undef)
 |  984674700: 0.0000000000e+00  (undef)

hmm not sure what is happening here, but the line in the perl
bindings looks quite simple to me:

                av_push(line,(isnan(*datai) ? &PL_sv_undef : newSVnv(*datai)));

anyone ?

tobi

 | #
 |
 | use lib '/usr/local/rrdtool-1.0.33/lib/perl';
 | use RRDs;
 | ($start,$step,$names,$data) = RRDs::fetch ("$ARGV[0]",'AVERAGE');
 | if ( $error = RRDs::error ) {
 |   print "rrdtool fetch failed: \"$error\"\n";
 |   exit 1;
 | }
 | $d_start = $start;
 | foreach $line (@$data) {
 |   print " $d_start: ";
 |   $d_start += $step;
 |   foreach $val (@$line) {
 |     printf "%1.10e ", $val;
 |     if ( ! $val ) { print " (undef)"; }
 |   }
 |   print "\n";
 | }
 |
 |
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