Cheshire Cat Computing

If I click on one graph, and then click on another graph, and then go back to the initial graph, I always get a blank frame instead of the graph, I have to wait about 5minutes before I can view the graph again.

Using the refresh button yields the same blank frame (no error message in the browser window, but the Apache access log did report a code 304 (Page not modified), putting a .htaccess file in the folder that says "Header set Pragma "no-cache"", yields a code 200, in the access log, but I still get a blank frame.

routers2 version 2.22,
windows 7 64bit,
xampp apache 2.2.21

Sometimes, if using IE for your browser, it will use an aggressive caching mode. You need to set it to 'check every time'.

Also, you need to verify that your workstation clock is in synch with the routers2 server's clock! If they are out by even a minute you can get odd behaviour from caching of images. Clock synch for the routers2/mrtg host is always important, but the client also needs to be synched if you want to have the caching working correctly.

Using the 'back' button can soetimes break the Routers2 interface, as the javascript causes multiple frames to refresh at once. This can break the autorefresh on occasion (though Ive not been able to duplicate it on demand)

The normal install sets the images to cache for a period of time reletive to their normal update frequency, which is relative to the data collection frequency.

With apache, you can change the .htaccess from the default provided by routers2 to specify no-cache for everything, if you prefer. However, I think your problems lie with the browser.

_________________
Steve Shipway
UNIX Systems, ITSS, University of Auckland, NZ
Woe unto them that rise up early in the morning... -- Isaiah 5:11

I'm using firefox primarily, but I have the same issue with IE and chrome also, and when I do ctrl-shift-r (in firefox) to bypass caching, I still have the issue (unless there is another key combo?),

I have the issue when running this on localhost (so no clock sync issues).
I'm having this issue when I just click on links and don't use the back button

I've tried using a .htaccess file (though I may of done it wrong), and it didn't help.

How would I be able to change the caching of the Images?

i know this is an old post but it still seems to be an issue.

I am using IIS7 webserver and a windows 2008 server with 2.20 of routers2 from firefox and i have exactly the same problem with graph not being added to the pages. When going to say CPU for a server graph is shown, then go to memory and get graph and then back to CPU and the graph is gone (and so is rest of frame after it..... On looking at the webserver I can see that the webserver process is looking the png file in question. Restart IIS to clear the lock and the problem is resolved until the the same operations is attempted and again the png is locked and does not display on the webpage frame of routers2.....

From some digging in code I have found problem RRDs::graph sometimes fails and crashes the perl program part way through generating the frame with the graph in it. Steve has mentioned in a post elsewhere the parameter list is very long and can make RRDs::graph fall over from time to time.

As I am using the latest version of RRDs in perl install I have a newer version to try and avoid problem is not an option....

So I have got around this problem as best as I can now by altering routers2.pl to call the code to regenerate the graph - instead of every time the page is rendered it is now only called if the rrd file has been updated since the graph was last generated (or its zero bytes because something has gone wrong with graph generation last time) :

Search for :

( $rrdoutput, $rrdxsize, $rrdysize ) = RRDs::graph(@params);
$e = RRDs::error();

and replace with :

if ((stat($thisgraph))[7] gt 0 && (stat($thisgraph))[9] gt RRDs::last($interfaces{$graphif}{rrd})) {
close(INFO);
} else {
( $rrdoutput, $rrdxsize, $rrdysize ) = RRDs::graph(@params);
$e = RRDs::error();
}

not perfect but the calls to the problem part of script happen much less now so the chances of having no graph displayed are much lower and its less work for the server to keep generating the graph when the data has not changed so a few watts of power saved too

This is in fact a separate issue, caused by a bug in the version of RRDTool you are using - early 1.3.x versions.

When in 'lazy' mode - the default - it will check to see if it needs to update the graph at all - if it is a very recent file, it doesnt bother. However, the bug causes it to return meaningless values for the images size which break other things.

You can get around this in the latest version of Routers2 by having the routers2.conf option 'lazy = no'

Steve

_________________
Steve Shipway
UNIX Systems, ITSS, University of Auckland, NZ
Woe unto them that rise up early in the morning... -- Isaiah 5:11