[rrd-users] Re: Graph Different

[Alex van den Bogaerdt]

Guilherme Barile wrote:
> 
> Hello
>  I just finished reading rrdtool's tutorial and now I can write a MRTG
> clone using it :)  Great, but if I wanted to have the same graphs as
> mrtg, i'd use mrtg, not rrdtool.

Not really... You could consider using rrdtool just because it uses
less resources.

>  What I want is graphs like mrtg but when the link is down or the
> packet loss goes up to 100% i'd like the backgroun to turn red...
>  Maybe when packets are lost, but less then 1005 (50% ?) i could have
> a yellow bg... There's an example of this on rrdtool homepage but not
> source code :( Also, they are not graphing bandwidth usage and packet
> loss on the same graph ...

If you really want the background to go red, you need to query
the database (use rrdtool graph with just a PRINT statement),
analyse the output and use the result to set a variabele.  This
variable can then be used in the graph script; in stead of a fixed
color.  Quick start, using a pseudo script language:

   get output of
   rrdtool graph /dev/null DEF:packetloss=.... PRINT:packetloss:MAX:%6.2lf
   into variable packetloss

   if packetloss > 50 then background="#FF0000" else background="#FFFFFF"
   rrdtool graph info.png -A PNG --color BACK:$background ...

If you want to change the color behind your line or area, you should
first draw a background using AREA and then overlay this with the
real line/area.  The background can be created by a CDEF that evaluates
to either NaN or INF.  If the computed value is INF, an AREA will fill
the space between the X-axis and the top of the graph.  If the value
is NaN, nothing will be shown.  Quick start:

   DEF:packetloss=.....
   CDEF:toomuch=packetloss,50,GE,INF,UNKN,IF
   AREA:toomuchFF0000:"Too much packetloss"
   LINE:packetloss#0000FF:Packetloss

Of course you should start simple (just one threshold) and when
this works you try to enhance your script.  My example code will
alert you when packetloss is 50% or more, assuming you're monitoring
a percentage.

HTH
-- 
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