Werk #15638: Predictive Levels: Supress levels for constant values

Component	Checks & agents
Title	Predictive Levels: Supress levels for constant values
Date	Aug 23, 2023
Level	Prominent Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.3.0b1 Not yet released Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME) 2.3.0b1 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME) 2.2.0p9 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME) 2.1.0p34 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk MSP (CME) 2.0.0p39 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk MSP (CME)

This change affects users of the option In relation to standard deviation from Predictive Levels.

Predictive Levels are computed by considering every data point matching the configured reference period. If the data never changes across these points in time, then the standard deviation is zero. Thus, the predicted levels will precisely equal to the predicted value. Previously, this would result in a CRIT. This happened no matter the levels set via In relation to standard deviation.

While the described behaviour is self-consistent, most of these alarms are undesired and diminish the usefulness of Predictive Levels.

With this Werk, no levels are applied, if the standard deviation is zero.

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