[rrd-developers] rrdcached measurements in Ganglia

Daniel.Pocock at barclayscapital.com Daniel.Pocock at barclayscapital.com
Tue Nov 11 10:02:13 CET 2008


> -----Original Message-----
> From: kevin brintnall [mailto:kbrint at rufus.net] 
> Sent: 11 November 2008 08:52
> To: Pocock, Daniel: IT (LDN)
> Cc: rrd-developers at lists.oetiker.ch
> Subject: Re: [rrd-developers] rrdcached measurements in Ganglia
> On Tue, Nov 11, 2008 at 08:48:34AM -0000, 
> Daniel.Pocock at barclayscapital.com wrote:
> > I'm thinking about writing a module for Ganglia to read the STATS 
> > output from rrdcached
> I'm doing something similar..

Ok, maybe we can collaborate on this instead of me re-inventing the

> What are you using to measure IO?

I've written a module that reads /proc/diskstats on Linux and kstat on
Solaris.  The results match with iostat output.

> > Before I start coding around the output of the STATS 
> command, do you 
> > envisage more changes in the imminent future?
> The format will not change.  However, your code should allow 
> for more stats to be added in the future, just in case.

Yes, I don't imagine making anything too inflexible - but on the other
hand, I was thinking that it might be useful to have a one line STATS
command, so that the Ganglia module can read the output with a single

> > Also, do you think it might be worthwhile storing things like the 
> > maximum value of the queue length between any two STATS queries?
> Can't imagine why we'd need this...  Plus, two un-related 
> clients could issue "STATS"; they'd have no way of knowing 
> when the previous one ran.

That is definitely a risk - but for simplicity, that could be mentioned
in the man page, and just assume that most people will only run a single
instance of gmond and rarely run the STATS command manually.

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