[collectd] Processes plugin

Florian Forster octo at verplant.org
Thu Jan 14 19:27:38 CET 2010

Hi Mark,

On Thu, Jan 14, 2010 at 10:41:10AM +0100, Florian Forster wrote:
> Yeah, sounds like an unsigned 32bit integer being cast to a signed one.

turns out the data was first stored in a long (32bit / 64bit, depending
on architecture), then a counter_t (unsigned 64bit) then cast to a
derive_t (signed 64bit).

I've changed this to use `derive_t' thorough the entire plugin. Not sure
if this fixes the problem's core, though: It seems like you're
missing all negative "counter" values. [*]

After taking a good look at the RRDtool sources it turns out that there
have been a number of incarnations of this bug over the year. The
symptoms change over the time, and one of those is that values with
leading hyphens are dismissed as incorrect. I've sent a patch fixing all
the problems I could think of to the RRDtool mailing list and it's been
applied already. [0]


[*] Though you'll need to write 2^63-1 bytes (roughly 9.2 Exabytes) for
    this, assuming Linux provides 64bit counters.
[0] <http://oss.oetiker.ch/rrdtool-trac/changeset/2001/trunk/program/src>
Florian octo Forster
Hacker in training
GnuPG: 0x91523C3D
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