[Xymon] rrd logs and graphs

[Jeremy Laidman]

On 04/03/2015 6:02 PM, "Vernon Everett" <everett.vernon at gmail.com> wrote:

> Looks like we might need to check with JC for more on that GOCLIENT thing.
> I just find it odd that it happened about the same time as the corruption.
> I haven't seen it again today, and haven't seen any other corruption
either.

If there's a correlation it might help us work out where the fault is. But
it might be only a symptom.

> As for the --debug option, it caused xymond_rrd to crash and burn,
dumping cores as we go.

Could be that thensame bug causing the crash during debug is also causing
the corrupt filename. Have you analyzed the core dumps?

> Don't think it started after an upgrade.
> Something I did notice, the problem appears to be limited to data only,
used to display graphs in trends.
> I am not seeing this for data when there is a status and data component.
> Or at least I haven't seen it yet.

Interesting. Maybe you could modify your script to send a status also?

> What are the implications of running with "--no-cache"?

I think then cache is only to save on disk I/O. If your disks aren't
"running hot" (ie queueing requests long enough to cause problems) then
youre probably OK to leave it.

> I have implemented this by adding "--no-cache" but if it's going to have
a long-term impact, I don't want to leave it that way indefinitely.

Some people have reported solving some other problems by disabling the
cache, with presumably no I'll effects.  For example
http://lists.xymon.com/archive/2009-November/026572.html. It's a
performance improvement that hasn't always been there and so is probably
not necessary for average size monitoring service. Also I think that if you
have operations staff that refresh lots of graphs (hence forcing the cache
to flush) you get minimal benefit from the cache.

But it all depends on how many RRD updates per second your server needs to
make, and how fast your disks and filesystem can update. If you have enough
RAM, your OS might have sufficient buffers to not need the cache anyway.

J
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