deviate

Watch: deviate

watch.deviate raises when one element strays from the others of the same pass: here, a processor left idle while the others work, read by SNMP.

How to read it

• per('processor', 'Processors') declares that the collector returns one value per processor, and 'per' => 'processor' on the output makes it so. deviate needs such an output.
• The watch compares each processor with the median of the others: 'warning' => 40 raises when it is more than 40 points away from it.
• 'side' => 'below': only a value under the median counts; above the other way, both (the default) either way.
• Under three processors kept in a pass, nothing is judged.
• snmp.walk returns array(suffix => value); foreach ($loads as $index => $load) gives both, and value('load', $load, 'cpu' . $index) names the element.

To adapt it

• Any set of like elements: the disks of an array, the nodes of a cluster, the links of an aggregate.