public CriticalRegion disallowDuperModelLockAcquisition(String regionDescription) {
        return disallowedDuperModeLockAcquisitionRegions.startCriticalRegion(regionDescription);
    }
Within the region, trying to accesss the duper model (without already having the lock)
will cause an IllegalStateException to be thrown.
service-monitor/src/main/java/com/yahoo/vespa/service/duper/DuperModelManager.java