On Tue, Sep 22, 2009 at 9:05 AM, Vladimir Vuksan <vli...@veus.hr> wrote:
> I guess a lot of the conversation depends on what you want and expect
> Ganglia to be used for. For example there are a lot of people out there
> that are using Ganglia for performance monitoring and using Nagios NRPE
> to get user level stats from the host. To me that is redundant.

indeed, this is one of the many flaws with the monitoring/alerting
setups we have today, it's almost like the people collecting metrics
and those making checks didn't like each other and never talked, but
have to meet in secret in the sysadmin's bedroom...

> Thus if
> you decide you are gonna use Ganglia for providing metric to e.g. Nagios
> you will have to go the route of parsing the Gmond XML. I checked on my
> cluster and each host uses about 15 kBytes (average) of XML to define
> metrics. This works well in small to mid size clusters however as soon
> as you get over certain threshold it breaks down. Let's say
> 200 hosts * 15 kB = 3 MB
> if I wanted to keep track of one metric that would be about 600 MBytes
> of traffic per minute or 10 Mbytes/sec just to fetch the whole XML tree.
> More metrics that need to be checked ie. swap_free and you may be doing
> quite a bit of network traffic. This is just to serve the XML and it
> doesn't take into account overhead processing and parsing data.
> You'll say wait a minute :-) if I was doing such a thing I would cache
> the data etc. I hear some people are doing just that ie.

/me raises hand

> storing XML on
> local storage. I have couple ideas myself but the point is that such a
> set up requires yet another thing to setup, monitor and maintain.

indeed, not to mention your data has to be cached for longer than it
could if there was less of it to exchange each time (on large setup
you need caching no matter what)

> Also perhaps REST API is not really the way to go but a simple HTTP
> interface would suffice.
> I hope this makes sense :-).

It did, except that last bit... how is a simple HTTP interface the way
to go but a REST API perhaps not? Given the pretty simple and easy to
represent data model I don't see how structuring your HTTP calls so
that they are RESTful is not the way to go. If you said that an http
interface is too much and a simpler TCP one would suffice I'd
disagreed, but understood, while I'm instead lost on the simple HTTP


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