[rrd-users] More comfortable chart display

Martin Sperl rrdtool at martin.sperl.org
Sun Jan 25 15:17:55 CET 2009


A colleague of mine has written a java-script a few years ago that was 
able to take a dynamically created rrd-graph (based on a cgi-script that 
takes arguments for start, end, min and max) and allowed us to zoom into 
the image by selecting the "interresting area". Sadly this code is no 
longer available to me (and also a copyright issue...).

This was working quite well, but was not perfect, as we were not able to 
enlarge the size of the image itself, as then all the scaling would have 
gone astray. Other effecting parameter are: Label of Y-Axis, Title 
(maybe multiline), font-size,... So there is the need to get the scale 
and the "graph area within the image" without to much guesswork or 
assumptions about the graph layout.

So what I see that you would need to create is:
* a cgi-script tat can create the graph dynamically based on the 
arguments you give - I believe that several people have creates some 
cgis like these, but as usual these tend to be highly "use-case" 
specific... This is really not very complex and you should be able this 
with a few lines of perl/php/ruby code (depending on available language 
* a javascript that does handle this "selection" and does a reload of 
the image as soon as the selection is done.

Then you should be able to handle your requirements for showing such a 
graph without having to create a separate graphing tool, which would 
introduce additional overhad and lead you to reinventing the wheel like 
how to do "Axis labels" placements (which RRD tool is handling quite nicely)

To avoid the "scaling" problems within the Image itself, maybe we 
should  think of how we can extend rrdtool so that it can embed the 
drawing area and the X/Y-scale information into the PNGs or JPGs - e.g. 
write EXIF information - and then have the javascript use the provided 
information for scale calculations.
(For the JavaScritpt accessing the information this code maybe a 
starting point: 

Actually I believe that a few people would like such a capability for 


alix-r wrote:
> Hello,
> I don't want to complain about the way RRDTOOL displays recorded data. I'm
> explicitly quite
> happy with all the options  RRDTOOL offers!
> Nevertheless, I'm looking for an other tool which can display the stored
> data (I converted them to XML)
> in a more comfortable way. 
> The reason is , I'm logging about 30 temperatures over a period of 3 month
> any minute. The data base
> is organized that way, that I can get all one minute temperatures over the
> hole 3 month. My problem
> now is to select a certain time area of my interest and zoom it, so I can
> identify the results of 
> certain external events. That is a bit difficult to realize with RRDTOOL
> GRAPH and quite time-consuming.
> (provided I used the right features of that really powerful tool).
> Does anybody know a tool which allows to display a XML data set generated by
> rrdtool , in a way  I could
> quickly move to a certain time position and quickly zoom in the area around
> that position ? I would
> prefer a tool running on Windows, but Linux would also be ok.
> Thank you very much.
> Robert

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