[rrd-users] Re: No graphic line's show up

Alex van den Bogaerdt alex at ergens.op.het.net
Fri Apr 25 17:10:17 MEST 2003

On Fri, Apr 25, 2003 at 04:18:23PM +0200, Sjaak Nabuurs wrote:

> What could be wrong ?
> I guess somthing wrong with timing


Two problems, both time related.

> # generate example in a FORNEXT LOOP This works fine showed a nice graph
> #     for ($t=$start; $t<$start+300*300; $t+=300){
> # RRDs::update $rrd, "$t:".(sin($t/3000)*50+70). " $t:".(sin($t/100)*50+30).
> " $t:".(sin($t/3000)*30+300).
> " $t:".(sin($t/3000)*50+10). " $t:".(sin($t/200)*50+10). "

You are using explicit times.  No problem, as long as you remember
what you're doing.

> RRDs::graph "$pngfile",
>   "--title", "HTTP data transfer, loadbalancing router VSM.",
>   "--vertical-label", "Waardes in Mbits",
>   "--start", "now",
>   "--end", "start+1d",

You are graphing from "now" to "now+1d".  This is wrong twice:

1) There will never be any data available for intervals in the future
2) You are not graphing the interval that you set using your update commands

"--start" defines the left hand side of the image
"--end" defines the right hand side of the image
Time flows from left to right.

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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