Werk #18346: Fix clustered services for offline node

Component

Checks & agents

Title

Fix clustered services for offline node

Date

Nov 19, 2025

Level

Trivial Change

Class

Bug Fix

Compatibility

Compatible - no manual interaction needed

Checkmk versions & editions

2.5.0b1 Not yet released	Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)
2.4.0p17	Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)
2.3.0p41	Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)

Hosts tagged with the criticality "Do not monitor" are treated as offline.

If a cluster contained such an offline node, monitoring of that cluster was broken.

Depending on the selected core, different error messages appeared in the web UI:

CMC: "unpack required a buffer of 4 bytes"
Nagios: "Failed to lookup IPv4 address of {hostname} via DNS"

These errors occurred because the cluster check attempted to retrieve check results for an offline node.

With this werk, offline cluster nodes are now ignored, just like regular offline hosts. This prevents the errors and ensures that cluster monitoring functions correctly even when some nodes are offline. No action is required to benefit from this fix.

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