> -----Original Message----- > From: Richard Mohr [mailto:[EMAIL PROTECTED] > Sent: Wednesday, May 16, 2007 2:57 PM > To: Matthew Chambers > Cc: ganglia-developers@lists.sourceforge.net > Subject: Re: [Ganglia-developers] About gmetad data source intervals > > On Wed, 2007-05-16 at 11:46 -0500, Matthew Chambers wrote: > > > I initially set up gmetad.conf with my data sources using default > > intervals (15sec). I then decided I wanted 10sec intervals so I > > changed the conf and restarted the service. I soon discovered that my > > hour graphs looked like bar graphs. > > Since I don't know what you gmetad.conf file looked like, I'll venture > to guess what changes you made. Then you can tell me if I am right. > > My guess is that you modified the "data_source" line to look something > like this: > > data_source 10 "cluster_name" <host1> <host2>... > > That way your gmetad would poll the gmond every 10 seconds. However, > you didn't specify a new "RRAs" line in gmetad.conf. Is that correct?
Correct. At the time I made the modification, I had no idea what an RRA even was. > That kind of behavior is not realistic. Different people want to > collect data at different intervals for different lengths of time. Some > people may want the smallest timestep data to span 2 hours instead of 1 > hour, or they could just as easily want it to span 30 minutes. Sure, > gmetad could determine the step size from the data_source line, multiply > it by the number of data points in the RRA definition, and find out what > time span that covers. But it has no way of knowing whether that time > span is "too short". Only the admin who configures gmetad can know > that. > As I understand it, the problem here is that the default RR[DA]s are created with a step size based on the interval specified in that data_source line, but the total number of rows in those RR[DA]s is still calculated as if the interval was 15 seconds for every data source. The default RRAs are set up for "hourly, daily, monthly, yearly" because I think those are by far the most common use cases. If those are the defaults and no custom RRAs have been specified but custom intervals HAVE been specified, the proper size of the RRAs can be reasonably calculated and compared to the existing RRAs based on those intervals instead of the default 15 second interval. If admins want other kinds of sampling/time periods then I agree with you that custom RRAs are the way to go and gmetad can disable its check if custom RRAs are specified. > The real problem with your case was that the web frontend didn't allow > you to view graphs for time periods of less than an hour. A 30 minute > graph would have allowed you to see the details in your data. But if > you look back through the mailing list, you should see some mention of > recent work to allow customizable graphs for the web frontend. I am not > sure if it is in the latest Ganglia release, but that might be of > interest to you. Not really. I still wanted the default time periods, I just wanted them to have slightly higher resolution. This too seems like a fairly common use case, but I could be wrong. -Matt Chambers ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Ganglia-developers mailing list Ganglia-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ganglia-developers
