static Timer.Context getTimeContext(final String opName) {
        return KVMetrics.timer(DB_TIMER, opName).time();
    }
Init the fencing token of new region.

@param parentKey the fencing key of parent region
@param childKey  the fencing key of new region
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/storage/BaseRawKVStore.java