[rrd-developers] rrdcached shutdown

Sebastian Harl sh at tokkee.org
Thu Sep 25 23:03:13 CEST 2008


On Thu, Sep 25, 2008 at 12:11:41PM -0500, kevin brintnall wrote:
> On Thu, Sep 25, 2008 at 06:25:44PM +0200, Sebastian Harl wrote:
> > > > RRDs out to disk..  When the daemon starts back up it can re-create its
> > > > memory state with the journal.
> > 
> > I don't think this is a good idea. When shutting down the daemon, I'd
> > expect it to finish it's job - e.g. I might not want to restart the
> > daemon, so I would lose data in that case. I agree that this is probably
> > a very uncommon case but I'm sure there are quite a few other examples
> > and I don't want to risk data loss even in very uncommon situations.
> I think it makes more sense to focus on how quickly the daemon can return
> to service with no data loss.  If we need to reboot for some reason, and
> the daemon is blocking shutdown for 20 minutes, that's a problem.

I see and agree that this might be a problem. However, I still think
that the _default_ behavior should follow the principle of least
surprise and imho this includes writing all data to the RRD files.

Providing an _optional_ way to only flush the journal sounds perfectly
fine to me. If that was your original intention then sorry for the

> > > > What do you think about an expedited shutdown if we are journaling
> > > > updates?  We could simply flush the journal and exit.
> > > 
> > > this would make sense to me ... maybe have different behaviour
> > > depending on the signal it gets ?
> > 
> > That won't work in this case. You cannot catch SIGKILL.
> We could catch SIGTERM for expedited shutdown and SIGINT for full-flush
> shutdown?  Then, each operator can decide which makes the most sense.

Sounds good to me.


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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