@Override
  public void abortTxn(AbortTxnRequest rqst) throws NoSuchTxnException, MetaException, TxnAbortedException {
    TxnType txnType = new AbortTxnFunction(rqst).execute(jdbcResource); 
    if (txnType != null) {
      if (transactionalListeners != null && (!rqst.isSetReplPolicy() || !TxnType.DEFAULT.equals(rqst.getTxn_type()))) {
        List<String> dbsUpdated = getTxnDbsUpdated(rqst.getTxnid());
        MetaStoreListenerNotifier.notifyEventWithDirectSql(transactionalListeners, EventMessage.EventType.ABORT_TXN,
            new AbortTxnEvent(rqst.getTxnid(), txnType, null, dbsUpdated), jdbcResource.getConnection(), sqlGenerator);
      }
    }
  }
Retry-by-caller note:
Worst case, it will leave an open txn which will timeout.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/TxnHandler.java