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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef CEPH_CONFIG_CACHER_H
#define CEPH_CONFIG_CACHER_H
#include "common/config_obs.h"
#include "common/config.h"
/**
* A simple class to cache a single configuration value.
* Points to note:
* - as get_tracked_conf_keys() must return a pointer to a null-terminated
* array of C-strings, 'keys' - an array - is used to hold the sole key
* that this observer is interested in.
* - the const cast should be removed once we change the
* get_tracked_conf_keys() to return const char* const * (or something
* similar).
*/
template <typename ValueT>
class md_config_cacher_t : public md_config_obs_t {
ConfigProxy& conf;
const char* keys[2];
std::atomic<ValueT> value_cache;
const char** get_tracked_conf_keys() const override {
return const_cast<const char**>(keys);
}
void handle_conf_change(const ConfigProxy& conf,
const std::set<std::string>& changed) override {
if (changed.count(keys[0])) {
value_cache.store(conf.get_val<ValueT>(keys[0]));
}
}
public:
md_config_cacher_t(ConfigProxy& conf,
const char* const option_name)
: conf(conf),
keys{option_name, nullptr} {
conf.add_observer(this);
std::atomic_init(&value_cache,
conf.get_val<ValueT>(keys[0]));
}
~md_config_cacher_t() {
conf.remove_observer(this);
}
ValueT operator*() const {
return value_cache.load();
}
};
#endif // CEPH_CONFIG_CACHER_H
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