[rrd-developers] Accelerator Daemon

Tobias Oetiker tobi at oetiker.ch
Tue Jun 24 23:37:49 CEST 2008

Today Florian Forster wrote:

> Hi Tobi,
> On Tue, Jun 24, 2008 at 10:28:08PM +0200, Tobias Oetiker wrote:
> > One big patch is fine ...
> okay.
> > a) make sure rrdtool will not write the rrd file directly if the
> >    daemon has data to write to it.
> I'm not convinced this is really necessary: That daemon solves a problem
> very big installations have. I don't expect this daemon to become the
> usual way of accessing RRD files but that a few administrators, with
> several thousand files to be updated, will use it to escape IO-hell. The
> kind of people I'm talking about knows how to create a separate account
> for `rrdcached' and hopefully does so.

cool idea ... rrdcached should run as a separate user that solves
the problem ... it should say so everywhere in the docs ...

> I guess my point is that the usual way of using RRDTool is _not_ by
> having a variety of users/programs to update the database. Usually there
> is exactly one process updating the file over and over again. And in
> 99.9% of all updated this it done automatically.


> If people want to screw up their RRD files, there are easier ways to do
> this. Update with a time stamp far in the future, for example.

The problem is that rrdtool is totally not forgiving when it comes
to updates ... one update and you have A lot of work ahead of you.
Scenario, there is that nice frontend which supports rrdcached and
you switch it on an off via a commandline option ... for some
reason the tool gets restarted without the option which the cache
daemon has not yet written all the data ... if it is a big
installation (io-hell) you get to fix A LOT of files ... So if we
can help it 'by design' then we should ...


Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902

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