ceph/src/common/config_obs.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #ifndef CEPH_CONFIG_OBS_H
  16 #define CEPH_CONFIG_OBS_H
  17
  18 #include <set>
  19 #include <string>
  20
  21 #include "common/config_fwd.h"
  22
  23 namespace ceph {
  24 /** @brief Base class for configuration observers.
  25  * Use this as a base class for your object if it has to respond to configuration changes,
  26  * for example by updating some values or modifying its behavior.
  27  * Subscribe for configuration changes by calling the md_config_t::add_observer() method
  28  * and unsubscribe using md_config_t::remove_observer().
  29  */
  30 template<class ConfigProxy>
  31 class md_config_obs_impl {
  32 public:
  33   virtual ~md_config_obs_impl() {}
  34   /** @brief Get a table of strings specifying the configuration keys in which the object is interested.
  35    * This is called when the object is subscribed to configuration changes with add_observer().
  36    * The returned table should not be freed until the observer is removed with remove_observer().
  37    * Note that it is not possible to change the set of tracked keys without re-subscribing. */
  38   virtual const char** get_tracked_conf_keys() const = 0;
  39   /// React to a configuration change.
  40   virtual void handle_conf_change(const ConfigProxy& conf,
  41                                   const std::set <std::string> &changed) = 0;
  42   /// Unused for now
  43   virtual void handle_subsys_change(const ConfigProxy& conf,
  44                                     const std::set<int>& changed) { }
  45 };
  46 }
  47
  48 using md_config_obs_t = ceph::md_config_obs_impl<ConfigProxy>;
  49
  50 #endif