missing

Watch: missing

watch.missing raises when expected elements are absent: here, the interface eth0 of a Linux.

How to read it

• The output is declared per (one value per interface); the watch looks at which interfaces have a value at this pass.
• array('critical' => array('eth0')): each name of the list with no value raises the level, once, with every missing name.
• It looks at every element returned, whatever the selection keeps: an interface left out of the selection is still present.
• The value itself does not matter: missing takes an output of any sort.

To adapt it

• The list of names is a setting: the administrator writes the interfaces of each host on the probe.
• Mount points, services, the members of a cluster: anything whose presence matters.