code: private void clearLock() {
        Object previousValue = noCacheStoreCache.remove(keyOfLock);
        if (previousValue!=null && trace) {
           log.tracef("Lock removed for index: %s", indexName);
        }
     }
docs: Removes the lock, without committing pending changes or involving transactions. Used by Lucene
  at Directory creation: we expect the lock to not exist in this case.