[rrd-users] rrdgraph never returns with small step

Alex van den Bogaerdt alex at ergens.op.het.net
Thu Jun 19 09:46:44 CEST 2008

On Wed, Jun 18, 2008 at 10:10:21PM -0400, Josh Wyatt wrote:

> This works fine... It does make a big file though, about 7.3MB.
> The update is via RRDs:
> $e=RRDs::update('bits.rrd','-t','00:01:02:03:04:05:06:07:08:09:10',"N$total");
> The way $total is built, it includes a preceding ':' so that a typical line looks like this:
> $e=RRDs::update('bits.rrd','-t','00:01:02:03:04:05:06:07:08:09:10',"N:35:11:13:12:12:14:10:10:604:591:11");
> And this updates the RRD every second, in a loop.

Not that I expect this to be related to the problem you report, but I
think you may want to consider using timestamps instead of 'N'. When
updates are a bit delayed (e.g. busy computer) it doesn't really matter
for 5-minute updates (e.g. 0.1 second on 300 seconds is 0.3%) but it
does for 1-second updates (e.g. 0.1 second on 1 second is 10%)

> Now, I try to graph:
> /usr/local/bin/rrdtool graph /home/graphs/all.png  -s -30s -w 200 -h 40 -a PNG
>  -A  \
> DEF:00=/home/graphs/bits.rrd:00:AVERAGE \
> LINE1:00#00cccc  

You don't need "--end" ?

Try to isolate the problem.

This is 30 seconds, on 200 pixels.  That is 6.66666.... pixels per
second.  It shouldn't be a problem, but just to be sure you should
try with something more sane, like -s-30s -w 300.

Try fetching the data (rrdtool fetch -s -30s /home/graphs/bits.rrd AVERAGE).
Does that hang, or not. If it does, the problem is probably somewhere
in the data collection part, else if will probably be in the graph part.

Try using another disk (no NFS, no data storage card, different filesystem.)
Try building RRDtool with/without mmap.

Try switching off the X-axis label. If it then works, try to find
a label setting which works for you.  E.g.

--x-grid none
--x-grid SECOND:1:SECOND:10:SECOND:10:0:%s

Do similar for the Y-axis.

Try another type of image, perhaps there's a problem in the graph

Try switching off titles and so on (especially if using non-ascii

Better yet: use "--no-legend" , so that no 'extra' will be in the way.

Alex van den Bogaerdt

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