@Override
  public MutexAPI getMutexAPI() {
    return mutexAPI;
  }
Isolation Level Notes
Plain: RC is OK
This will find transactions that have timed out and abort them.
Will also delete locks which are not associated with a transaction and have timed out
Tries to keep transactions (against metastore db) small to reduce lock contention.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/TxnHandler.java