When trying to upgrade a Foglight Agent Manager (FglAM) multi state installation, only 2 FglAMs got upgraded to the new version (5.8.2), the third one failed without error.
When triggering the upgrade for the failed FglAM again, nothing happen.
For a multi-state FglAM installation the following can happen: the error might be a result of upgrade process not including all of the FglAM instances that are part of this installation. When an FglAM instance from multi-state directory is not included in the upgrade, then it does not get the restart command when the upgrade of the other hosts completes. If you then decide to initiate the upgrade to this FglAM instance, it will attempt to overwrite the files that are in-use by the other FglAM state instances; resulting in the error that is being reported here.
The following can be found in the FglAM log files: