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Werk #22415: mtr: do not lose all targets on an agent plugin error

Component Checks & agents
Title mtr: do not lose all targets on an agent plugin error
Date Sep 22, 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
2.5.0p15
Not yet released
Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT
2.4.0p38
Not yet released
Checkmk Community, Checkmk Pro, Checkmk Ultimate, Checkmk Cloud, Checkmk Ultimate MT

When the MTR agent plugin failed to interpret one of its own traceroute runs, it wrote an error banner followed by a second line holding the raw output it had choked on. Checkmk recognised the banner but not the line after it, and tried to read a target host and a hop count from it. The section failed with IndexError: list index out of range, a crash report was created on every check cycle, and none of the MTR services on that host were updated any more -- including the targets the plugin had measured successfully.

Lines too short to hold a target and a hop count are now ignored. The targets that were measured are monitored again.

The error reported by the agent plugin itself is not shown anywhere in Checkmk; it only no longer stops the remaining targets from being monitored.

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