private String getCurrentUser(HiveMetaStoreAuthorizableEvent authorizableEvent) {
    return authorizableEvent.getAuthzContext().getUGI().getShortUserName();
  }
HiveMetaStoreAuthorizer :  Do authorization checks on MetaStore Events in MetaStorePreEventListener
ql/src/java/org/apache/hadoop/hive/ql/security/authorization/plugin/metastore/HiveMetaStoreAuthorizer.java