[rrd-users] Precise Value Graphing Help Needed

Kevin Elliott kelliott at dhapdigital.com
Mon May 8 22:24:40 MEST 2006

Greetings fellow RRDTool users,

I am writing today in an attempt to diagnose why I am unable to properly 
visualize exact last data (using GAUGE) in my rrdtool based historic 
tracking instead of what appears to be averaging of some sort.

WebLogic JDBC and Thread Pool Counts are the nature of our data. We are 
retrieving this information from production WL servers using WLShell, a 
java-based "shell" to WebLogic. We are creating an instance of our 
custom wlshell script, and using a loop inside to generate data for 5 
minute intervals. After data is retrieved, the wlshell script calls a 
perl script that uses RRDTool libraries to update the rrd. Since the 
connection to the production servers over our VPN seems to vary in 
latency all the time, the time it takes to retrieve the data we're 
requesting can change, so the 5 minute intervals are more than likely 
not exact.

My problem is that we're trying to see exact values at any given point 
in time (and atleast for the last 28 hours graph), rather than any sort 
of averaging. It is important to us that we know that around 11:05am, 
there was a spike of 10 connections, versus some average that says 6.7. 
We are seeing all sorts of decimals, and not whole integers as expected.

Our perl script contains the code to create the RRD, and we're using 
something like:

if ( ! -f $rrdfilename ) {
        print "WARN: RRD file ($rrdfilename) not present, creating...\n";
        @rrdCreateArgs = ($rrdfilename, "-s", int($rrdInterval * 60));
        if (($rrdHeartBeat = int($rrdInterval * 60) *2) < 600) {
                $rrdHeartBeat = 600;
        foreach $iterator (0 .. $#FIELDS) {
                push @rrdCreateArgs, "DS:" . $FIELDS[$iterator] . 
        push @rrdCreateArgs, "RRA:LAST:0.5:1:800";
        push @rrdCreateArgs, "RRA:LAST:0.5:12:800";
        push @rrdCreateArgs, "RRA:LAST:0.5:264:800";

print "Creating RRDfile \"$rrdfilename\" with create string = |" . 
join('\n', at rrdCreateArgs) . "|\n";

        my $error = RRDs::error();
        if ($error) {
                die "ERROR: Cannot create RRDfile \"$rrdfilename\", 
error = $error\n";

Our step size is 300. Instead of seeing values of 1 on the rrdgraph, 
we're seeing 0.2, and 0.6, etc. Some values do seem to have a plot of 2, 
but only because they are consistently at the value of 2, and don't vary 
as often. All datasources are type GAUGE.

Are there any recommendations for plotting unaveraged precise 
at-the-moment data? I just want to plot values at 5 minute intervals 
that go up and down per interval. We seem to have exhausted the 
documentation, and have search the web for similar strategies. I think 
we're still not grasping the proper way to do this.

Sincerest Regards,


Kevin Elliott
DHAP Digital, Inc

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