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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
#pragma once
#include <map>
#include <set>
#include <string>
#include "common/config_tracker.h"
class ConfigValues;
// @c ObserverMgr manages a set of config observers which are interested in
// the changes of settings at runtime.
template<class ConfigObs>
class ObserverMgr : public ConfigTracker {
// Maps configuration options to the observer listening for them.
using obs_map_t = std::multimap<std::string, ConfigObs*>;
obs_map_t observers;
public:
typedef std::map<ConfigObs*, std::set<std::string>> rev_obs_map;
typedef std::function<void(ConfigObs*, const std::string&)> config_gather_cb;
// Adds a new observer to this configuration. You can do this at any time,
// but it will only receive notifications for the changes that happen after
// you attach it, obviously.
//
// Most developers will probably attach their observers after global_init,
// but before anyone can call injectargs.
//
// The caller is responsible for allocating observers.
void add_observer(ConfigObs* observer);
// Remove an observer from this configuration.
// This doesn't delete the observer! If you allocated it with new(),
// you need to delete it yourself.
// This function will assert if you try to delete an observer that isn't
// there.
void remove_observer(ConfigObs* observer);
// invoke callback for every observers tracking keys
void for_each_observer(config_gather_cb callback);
// invoke callback for observers keys tracking the provided change set
template<class ConfigProxyT>
void for_each_change(const std::set<std::string>& changes,
ConfigProxyT& proxy,
config_gather_cb callback, std::ostream *oss);
bool is_tracking(const std::string& name) const override;
};
// we could put the implementations in a .cc file, and only instantiate the
// used template specializations explicitly, but that forces us to involve
// unused headers and libraries at compile-time. for instance, for instantiate,
// to instantiate ObserverMgr for seastar, we will need to include seastar
// headers to get the necessary types in place, but that would force us to link
// the non-seastar binaries against seastar libraries. so, to avoid pulling
// in unused dependencies at the expense of increasing compiling time, we put
// the implementation in the header file.
template<class ConfigObs>
void ObserverMgr<ConfigObs>::add_observer(ConfigObs* observer)
{
const char **keys = observer->get_tracked_conf_keys();
for (const char ** k = keys; *k; ++k) {
observers.emplace(*k, observer);
}
}
template<class ConfigObs>
void ObserverMgr<ConfigObs>::remove_observer(ConfigObs* observer)
{
[[maybe_unused]] bool found_obs = false;
for (auto o = observers.begin(); o != observers.end(); ) {
if (o->second == observer) {
observers.erase(o++);
found_obs = true;
} else {
++o;
}
}
ceph_assert(found_obs);
}
template<class ConfigObs>
void ObserverMgr<ConfigObs>::for_each_observer(config_gather_cb callback)
{
for (const auto& [key, obs] : observers) {
callback(obs, key);
}
}
template<class ConfigObs>
template<class ConfigProxyT>
void ObserverMgr<ConfigObs>::for_each_change(const std::set<std::string>& changes,
ConfigProxyT& proxy,
config_gather_cb callback, std::ostream *oss)
{
// create the reverse observer mapping, mapping observers to the set of
// changed keys that they'll get.
std::string val;
for (auto& key : changes) {
auto [first, last] = observers.equal_range(key);
if ((oss) && !proxy.get_val(key, &val)) {
(*oss) << key << " = '" << val << "' ";
if (first == last) {
(*oss) << "(not observed, change may require restart) ";
}
}
for (auto r = first; r != last; ++r) {
callback(r->second, key);
}
}
}
template<class ConfigObs>
bool ObserverMgr<ConfigObs>::is_tracking(const std::string& name) const
{
return observers.count(name) > 0;
}
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