[collectd] MySQL plugin reports wrong numbers on mysqld restart

[matthew sporleder]

On Mon, Sep 27, 2010 at 7:44 AM, Bostjan Skufca <bostjan at a2o.si> wrote:
> Hi all!
>
> Has anyone else noticed that MySQL plugin reports wrong numbers when
> mysql is restarted and collectd is not?
> It seems like it takes absolute value of i.e. queries per second (0
> when mysql is restarted minus i.e. 8 million just before restart) and
> calculates abs(- 8 million) = 8Mqps.
> If I restart MySQL every 2 months there is nothing I can see on the
> graphs because those restart spikes are so high that everything else
> is depressed down to zero.
>
> Does anyone have a fix/suggestion of fix for this?
>

What is the data type being used by the graphs?  It could be a COUNTER
vs DERIVE situation to handle the reset.

For your current graphs try adding a -u (upper limit).

Or you might also be able to find a way to kill those bad values from
the actual db if you take some backups first.  :)