private User getActiveUser(ObserverContext<?> ctx) throws IOException {
    // for non-rpc handling, fallback to system user
    Optional<User> optionalUser = ctx.getCaller();
    if (optionalUser.isPresent()) {
      return optionalUser.get();
    }
    return userProvider.getCurrent();
  }
Check if user global/namespace/table HDFS acls is already set
hbase-server/src/main/java/org/apache/hadoop/hbase/security/access/SnapshotScannerHDFSAclController.java