Ben Hartshorne wrote:
On Tue, Aug 08, 2006 at 04:22:41PM +0100, Ian Wootten wrote:
I am facing a problem in that I would like short-segment up to date
information from ganglia in order to monitor services after invocation.
One method I have heard of that achieves something similar; write a
separate module that interprets the XML feed directly.
This works well, and I've done it in a single page of code so it's
simple stuff. It becomes more of a chore when you want to actually store
that data. For short periods it's fine, but if you got a lot of machines
and you don't cycle out data the database will get really big really fast.
The other thing to consider is how often the xml updates. Clients
running gmond only report at set intervals, so if you're trying to get
information once a second you'll be unhappy with the results. This, in
combination with gmetad's write intervals, is why the rrds have the
'NaN' holes in them. Writing your own module may improve getting real
actual numbers, but it won't improve the quality of the data.
Newer versions of ganglia allow you to customize update intervals, but
on a big network setting values too frequent will generate a lot of
traffic, and probably slow the gmetad server to a crawl with all the rrd
updates.
