The SCA charm's enable_daily_store_kpi only executes once, when the nrpe-external-master relation is available, the service is active and set up, the unit is the leader, and enable_daily_store_kpi has not yet run. This can result in the check_daily_store_kpi-state-fileage check being written out to /var/lib/nagios/export with a bad hostname, as charmhelpers.contrib.charmsupport.nrpe.NRPE only calculates the right hostname one nagios_hostname has been set by the other end of the nrpe-external-master relation, but the function can run before that happens. Nagios updates then fail until the check export is corrected or removed.
We should probably execute enable/disable_daily_store_kpi as appropriate on every hook except update-status, matching the behaviour of more modern charms and ensuring that relation and config changes are respected, without adding disruptive restarts on regular operations like update-status.
