dynamic_config::Source Class Reference

Table of Contents

• Public Types
• Public Member Functions
• Detailed Description
• Member Typedef Documentation
• DiffEventSource
• SnapshotEventSource
• Constructor & Destructor Documentation
• Source()
• Member Function Documentation
• GetCopy()
• GetSnapshot()
• UpdateAndListen() [1/3]
• UpdateAndListen() [2/3]
• UpdateAndListen() [3/3]

A client for easy dynamic config fetching in components. More...

#include <userver/dynamic_config/source.hpp>

Public Types
using	SnapshotEventSource = concurrent::AsyncEventSource< const Snapshot & >
using	DiffEventSource = concurrent::AsyncEventSource< const Diff & >

Public Member Functions
	Source (impl::StorageData &storage)
	Source (const Source &)=default
	Source (Source &&)=default
Source &	operator= (const Source &)=default
Source &	operator= (Source &&)=default
Snapshot	GetSnapshot () const
template<typename Key >
VariableSnapshotPtr< Key >	GetSnapshot (Key key) const
template<typename Key >
VariableOfKey< Key >	GetCopy (Key key) const
template<typename Class >
concurrent::AsyncEventSubscriberScope	UpdateAndListen (Class *obj, std::string_view name, void(Class::*func)(const dynamic_config::Snapshot &config))
template<typename Class >
concurrent::AsyncEventSubscriberScope	UpdateAndListen (Class *obj, std::string_view name, void(Class::*func)(const dynamic_config::Diff &diff))
	Subscribes to dynamic-config updates with information about the current and previous states.
template<typename Class , typename... Keys>
concurrent::AsyncEventSubscriberScope	UpdateAndListen (Class *obj, std::string_view name, void(Class::*func)(const dynamic_config::Snapshot &config), Keys... keys)
	Subscribes to updates of a subset of all configs.
SnapshotEventSource &	GetEventChannel ()

Detailed Description

A client for easy dynamic config fetching in components.

After construction, dynamic_config::Source can be copied around and passed to clients or child helper classes.

Usually retrieved from components::DynamicConfig component.

Typical usage:

namespace myservice::smth {
 
namespace {
int ParseRuntimeCfg(const dynamic_config::DocsMap& docs_map) {
  return docs_map.Get("SAMPLE_INTEGER_FROM_RUNTIME_CONFIG").As<int>();
}
constexpr dynamic_config::Key<ParseRuntimeCfg> kMyConfig{};
}  // namespace
 
int Component::DoSomething() const {
  // Getting a snapshot of dynamic config.
  const auto runtime_config = config_.GetSnapshot();
  return runtime_config[kMyConfig];
}
 
}  // namespace myservice::smth

Examples

components/component_sample_test.hpp.

Definition at line 78 of file source.hpp.

Member Typedef Documentation

DiffEventSource

using dynamic_config::Source::DiffEventSource = concurrent::AsyncEventSource<const Diff&>

Definition at line 81 of file source.hpp.

SnapshotEventSource

using dynamic_config::Source::SnapshotEventSource = concurrent::AsyncEventSource<const Snapshot&>

Definition at line 80 of file source.hpp.

Constructor & Destructor Documentation

Source()

dynamic_config::Source::Source ( impl::StorageData &  storage )

explicit

For internal use only. Obtain using components::DynamicConfig or dynamic_config::StorageMock instead.

Member Function Documentation

GetCopy()

template<typename Key >

VariableOfKey< Key > dynamic_config::Source::GetCopy ( Key  key ) const

inline

Definition at line 101 of file source.hpp.

GetSnapshot()

template<typename Key >

VariableSnapshotPtr< Key > dynamic_config::Source::GetSnapshot ( Key  key ) const

inline

Definition at line 96 of file source.hpp.

UpdateAndListen() [1/3]

template<typename Class >

concurrent::AsyncEventSubscriberScope dynamic_config::Source::UpdateAndListen ( Class *  obj, std::string_view  name, void(Class::*)(const dynamic_config::Diff &diff)  func  )

inline

Subscribes to dynamic-config updates with information about the current and previous states.

Subscribes to dynamic-config updates using a member function, named OnConfigUpdate by convention. Also constructs dynamic_config::Diff object using std::nullopt and current config snapshot, then immediately invokes the function with it (this invocation will be executed synchronously).

Note

Callbacks occur in full accordance with components::DynamicConfigClientUpdater options.

Warning

In debug mode the last notification for any subscriber will be called with std::nullopt and current config snapshot.

Example usage:

  void OnConfigUpdate(const dynamic_config::Diff& diff_data) {
    if (!diff_data.previous) return;
 
    const auto& previous = *diff_data.previous;
    const auto& current = diff_data.current;
    if (previous[kBoolConfig] != current[kBoolConfig]) {
      OnBoolConfigChanged();
    }
    if (previous[kDummyConfig].foo != current[kDummyConfig].foo) {
      OnFooChanged();
    }
  }
  void OnBoolConfigChanged() { bool_config_change_counter_++; }
  void OnFooChanged() { foo_interesting_event_counter_++; }

Parameters

obj	the subscriber, which is the owner of the listener method, and is also used as the unique identifier of the subscription
name	the name of the subscriber, for diagnostic purposes
func	the listener method, named OnConfigUpdate by convention.

Returns

a concurrent::AsyncEventSubscriberScope controlling the subscription, which should be stored as a member in the subscriber; Unsubscribe should be called explicitly

See also

based on concurrent::AsyncEventSource engine

dynamic_config::Diff

Definition at line 167 of file source.hpp.

UpdateAndListen() [2/3]

template<typename Class >

concurrent::AsyncEventSubscriberScope dynamic_config::Source::UpdateAndListen ( Class *  obj, std::string_view  name, void(Class::*)(const dynamic_config::Snapshot &config)  func  )

inline

Subscribes to dynamic-config updates using a member function. Also immediately invokes the function with the current config snapshot (this invocation will be executed synchronously).

Note

Callbacks occur in full accordance with components::DynamicConfigClientUpdater options.

Parameters

obj	the subscriber, which is the owner of the listener method, and is also used as the unique identifier of the subscription
name	the name of the subscriber, for diagnostic purposes
func	the listener method, named OnConfigUpdate by convention.

Returns

a concurrent::AsyncEventSubscriberScope controlling the subscription, which should be stored as a member in the subscriber; Unsubscribe should be called explicitly

See also

based on concurrent::AsyncEventSource engine

Definition at line 123 of file source.hpp.

UpdateAndListen() [3/3]

template<typename Class , typename... Keys>

concurrent::AsyncEventSubscriberScope dynamic_config::Source::UpdateAndListen ( Class *  obj, std::string_view  name, void(Class::*)(const dynamic_config::Snapshot &config)  func, Keys...  keys  )

inline

Subscribes to updates of a subset of all configs.

Subscribes to dynamic-config updates using a member function, named OnConfigUpdate by convention. The function will be invoked if at least one of the configs has been changed since the previous invocation. So at the first time immediately invokes the function with the current config snapshot (this invocation will be executed synchronously).

Note

Сallbacks occur only if one of the passed config is changed. This is true under any components::DynamicConfigClientUpdater options.

Warning

To use this function, configs must have the operator==.

Parameters

obj	the subscriber, which is the owner of the listener method, and is also used as the unique identifier of the subscription
name	the name of the subscriber, for diagnostic purposes
func	the listener method, named OnConfigUpdate by convention.
keys	config objects, specializations of dynamic_config::Key.

Returns

a concurrent::AsyncEventSubscriberScope controlling the subscription, which should be stored as a member in the subscriber; Unsubscribe should be called explicitly

See also

based on concurrent::AsyncEventSource engine

Definition at line 199 of file source.hpp.

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The documentation for this class was generated from the following file:

• userver/dynamic_config/source.hpp