Checkmk Werk 10041: Reduce apache memory usage + Change check parameters API

Lars Michelsen lm at
Mon Sep 16 08:49:30 CEST 2019

ID:          10041
Title:       Reduce apache memory usage + Change check parameters API
Component:   WATO
Level:       2
Class:       Bug fix
Version:     1.7.0i1

We recognized that the 1.6 check parameter (ruleset) plugin mechanism (which
was based on classes and using the python abc module) consumed a lot more
memory than the previous plugin API.

The apache processes were ~50% bigger than in previous Checkmk releases which a
too large growth. The problem is that the apache processes are part of a
dynamic process pool which can scale from 5 to 64 processes (in the default
config).  When your apache processes use 130 MB of memory, this means that you
would need to have ~8 GB of memory available to be able to handle high usage
peaks. In such a situation a single process growth of 50% is relevant and
should be avoided if possible.

If you have already ported your WATO check parameter plugins to 1.6 you will
now have to port it to the new mechanism.

The new plugin API for registering check parameters is similar to the 1.5 API,
but more explicit to make it easier to understand. For example the 'logins'
check parameter declaration looks like this:

from cmk.gui.i18n import _
from cmk.gui.valuespec import (

from cmk.gui.plugins.wato import (

def _parameter_valuespec_logins():
return Tuple(
help=_("This rule defines upper limits for the number of logins on a system."),
Integer(title=_("Warning at"), unit=_("users"), default_value=20),
Integer(title=_("Critical at"), unit=_("users"), default_value=30)

title=lambda: _("Number of Logins on System"),

More information about the checkmk-werks-lvl2 mailing list