Check_MK Werk 1409: Extended Check_MK-API: check function may return None

Mathias Kettner mk at
Tue Sep 30 08:26:10 CEST 2014

ID:          1409
Title:       Extended Check_MK-API: check function may return None
Component:   Checks & Agents
Level:       2
Class:       New Feature
Version:     1.2.5i6

A check function may now return <tt>None</tt> (or simply end without
returning anything). This will no longer create an exception but return
state <tt>UNKNOWN</tt> and - depending on the type of the check -
one of the following outputs:

<tt>Item not found in SNMP data</tt>

<tt>Item not found in agent output</tt>

This means that for the typical check that loops through the agent
output looking for its item now does not need to manually do a

return 3, "Something not found in agent output"

anymore. This is now the default case. This has several advantages:

<li>You save some code in the check implementation.</li>
<li>The output of the various checks is unified.</li>
<li>A future Check_MK version can easily have a rule for changing the state
in such cases from UNKNOWN to WARN or CRIT.</li>

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