Werk #22103: Check_MK Discovery: do not crash on older periodic discovery rules

Component

Checks & agents

Title

Check_MK Discovery: do not crash on older periodic discovery rules

Date

Aug 6, 2026

Level

Trivial Change

Class

Bug Fix

Compatibility

Compatible - no manual interaction needed

Checkmk versions & editions

3.0.0b1 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.5.0p12 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.4.0p36 Not yet released	Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

After upgrading, the "Check_MK Discovery" service of a host could go to UNKNOWN with a crash report ("check failed - please submit a crash report!") showing the exception KeyError: 'update_changed_service_parameters'.

This happened when a "Periodic service discovery" rule using a custom rediscovery mode had been stored before the "Update service parameters" option was introduced -- for example rules that were created via the REST API in an early 2.4 version and never re-saved afterwards.

The discovery check now tolerates these older rules by treating the missing "Update service parameters" option as disabled, and no longer crashes.

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