[collectd] meta and rrdcached

Sebastian Harl sh at tokkee.org
Wed Oct 15 09:49:06 CEST 2008

Hi Oleg,

On Mon, Oct 13, 2008 at 10:05:28PM +0400, Oleg King wrote:
> I was absent for a while

Welcome back then :-)

> 1. in 4.5.0 "The concept of "notification meta data" has been
> introduced.". What is it?

I have not looked into that in detail so far. So, I guess, it's up to
Florian to explain that ;-)

> 2. I have found rrdcached plugin source in source tree. What is it?
> How to use it?

RRDtool 1.4 (which is currently in development, I don't know of any ETA)
will ship a daemon called RRDcacheD which basically is a generic
implementation of the caching mechanism implemented in the "rrdtool"
plugin plus some further enhancements (which might be "backported" to
the rrdtool plugin as well some time). See [1] for further details.

The collectd "rrdcached" plugin can be used to send values to that
daemon instead of writing to RRD files directly. Also, that daemon
provides some statistics which may be collected by the plugin.


> 3. Is there is possibility to prevent some (not needed) rrd files
> from writing on disk (just skip info in rrdtool plugin) to reduce
> disk load?

Not yet. However, this will be possible using the "filter" mechanism
which has been introduced by my latest patch (src/plugin.[ch]: Added
support for "filter" callbacks.) which I've just sent to the list a
couple of minutes ago.

I'm planing to write a "filter_pcre" plugin which may then be used to
filter and / or rewrite values based on Perl-compatible regular


Sebastian "tokkee" Harl +++ GnuPG-ID: 0x8501C7FC +++ http://tokkee.org/

Those who would give up Essential Liberty to purchase a little Temporary
Safety, deserve neither Liberty nor Safety.         -- Benjamin Franklin

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