Werk #22082: mrpe: don't crash on metric names the plug-in cannot use

Component

Checks & agents

Title

mrpe: don't crash on metric names the plug-in cannot use

Date

Jul 31, 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
2.5.0p11	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

An MRPE service could go to UNKNOWN with "check failed - please submit a crash report!", the crash report showing TypeError: invalid character(s) in metric name.

MRPE turns the performance data labels of the wrapped Nagios plug-in into Checkmk metric names, and these must not contain a space, colon, slash or backslash. A plug-in labelling its metrics with, for example, a mount point (/=1234MB;;;0;13717, as check_disk does) therefore crashed the whole service.

Such a metric is now reported as "Undefined metric: ..." with state UNKNOWN, which is how MRPE already handled performance data it could not interpret. The plug-in output and all other metrics of the same service are shown as usual.

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