code: public boolean permit(ReqContext context, String operation, Map topology_conf) {
          LOG.info("[req " + context.requestID() + "] Access " + " from: " +
                  (context.remoteAddress() == null ? "null" : context.remoteAddress().toString())
                  + (context.principal() == null ? "" : (" principal:" + context.principal())) + " op:" + operation
                  + (topology_conf == null ? "" : (" topoology:" + topology_conf.get(Config.TOPOLOGY_NAME))));
          return false;
      }
docs: permit() method is invoked for each incoming Thrift request
  
  @param context       request context
  @param operation     operation name
  @param topology_conf configuration of targeted topology
  @return true if the request is authorized, false if reject