code: public int refreshServiceAcl() throws IOException {
      // Get the current configuration
      Configuration conf = getConf();
      
      // Create the client
      RefreshAuthorizationPolicyProtocol refreshProtocol = 
        (RefreshAuthorizationPolicyProtocol) 
        RPC.getProxy(RefreshAuthorizationPolicyProtocol.class, 
                     RefreshAuthorizationPolicyProtocol.versionID, 
                     NameNode.getClientProtocolAddress(conf), getUGI(conf), conf,
                     NetUtils.getSocketFactory(conf, 
                                               RefreshAuthorizationPolicyProtocol.class));
      
      // Refresh the authorization policy in-effect
      refreshProtocol.refreshServiceAcl();
      
      return 0;
    }
docs: Refresh the authorization policy on the {@link NameNode}.
  @return exitcode 0 on success, non-zero on failure
  @throws IOException