Matt,
I'm not sure I like the idea of outputting to /dev/null, it seems like
we will be making the web server twice as much raster work and
increasing the load unnecessarily.
Also I thought this problem had already been solved by removing width
and height attributes from the img tags, in web frontend version 3.0.5,
but I could be mistaken.
Cheers,
Ian
Matthew Chambers wrote:
Hi all,
I recently started using Ganglia on our Mac Mini cluster and I noticed
that the graphs are resized from their native size so that they fit
the templates. This didn't make a lot of sense to me, so I edited the
system so that the images returned by graph.php calls are used as-is.
I added two variables "sx" and "sy" which are passed in the graph.php
call specifying the desired width and height of the output image.
This approach means that, at least for the image calls which are
fully specified from the templates, the dimensions can be specified in
the template and needn't be worried about anywhere else. When I made
this modification I discovered that the width and height that rrdgraph
takes are actually the dimensions of the canvas (the inside box that
the actual graph is plotted on), and they don't include the outer box.
Rrdgraph does provide a way to get the final image's dimensions
(--imginfo), but it is not possible to use it while also using the
standard output mode (which is what the graph.php call does). So I
added a second call in graph.php which writes to /dev/null and simply
parses the output dimensions and adjusts the dimensions given to the
second call by the amount necessary to make the final dimensions match
the "sx" and "sy" variables. Since the "z" variable is obsolete but
was still used to change the graph style slightly for the host graphs,
I changed it to a "formtype" variable ("f") with values of "compact"
or "normal." Oh, I also changed the images to PNG instead of GIF
since the rrdtool documentation says that PNGs are generated as fast
or faster and are as small or smaller than GIFs. Here's the code:
#
# Generate the rrdtool graph command.
#
if ($formtype != "compact")
{
$command = RRDTOOL . " graph /dev/null --start $start
--end $end ".
"--width $width --height $height $upper_limit
$lower_limit ".
"--title '$title' $vertical_label $extras $background ".
" --imgformat 'PNG' --imginfo '%s\n%lu %lu' ".
$series;
$imginfo = exec($command);
$dims = explode(" ", $imginfo);
$width = $width - ($dims[0]-$width);
$height = $height - ($dims[1]-$height);
}
$command = RRDTOOL . " graph - --start $start --end $end ".
"--width $width --height $height $upper_limit $lower_limit ".
"--title '$title' $vertical_label $extras $background ".
#"--imgformat 'PNG' ".
"--step 5 ".
$series;
There are a few problems with this approach: 1) /dev/null is platform
specific (are there other parts of Ganglia that are already platform
specific so that this isn't such an issue?); 2) if the layout of the
graph's legend changes when the dimensions are adjusted, the
adjustments won't be correct, and I'm not sure what the best approach
is to fix this. Let me know what you guys think about this approach.
If it's satisfactory, I'll submit the changes to the repository.
Also, has there been any discussion about using SVG instead of raster
formats for the graph output? It would introduce serious user agent
compatibility considerations, but it would provide quite a lot of
potential benefits (interactivity, anyone?). Rrdtool's SVG output
would need to be improved, though.
Thanks,
Matt Chambers
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