1 files changed, 39 insertions, 13 deletions

diff --git a/src/p2p/data_logger.hpp b/src/p2p/data_logger.hpp
index 50beb847a..215912167 100644
--- a/src/p2p/data_logger.hpp
+++ b/src/p2p/data_logger.hpp
@@ -13,34 +13,60 @@ namespace epee
 {
 namespace net_utils
 {
+
+enum class data_logger_state { state_before_init, state_during_init, state_ready_to_use, state_dying };
 	
+/***
+@note: use it ONLY via singleton! It will be spawned then, and will auto destruct on program exit.
+@note: do call ::kill_instance() before exiting main, at end of main. But before make sure no one else (e.g. no other threads) will try to use this/singleton
+@note: it is not allowed to use this class from code "runnig before or after main", e.g. from ctors of static objects, because of static-creation-order races
+@note: on creation (e.g. from singleton), it spawns a thread that saves all data in background
+*/
 	class data_logger {
 		public:
-			static data_logger &get_instance();
-			data_logger(const data_logger &ob) = delete;
+			static data_logger &get_instance(); ///< singleton
+			static void kill_instance(); ///< call this before ending main to allow more gracefull shutdown of the main singleton and it's background thread
+			~data_logger(); ///< destr, will be called when singleton is killed when global m_obj dies. will kill theads etc
+
+		private:
+			data_logger(); ///< constructor is private, use only via singleton get_instance
+
+		public:
+			data_logger(const data_logger &ob) = delete; // use only one per program
 			data_logger(data_logger &&ob) = delete;
-			void add_data(std::string filename, unsigned int data);
-			static std::atomic<bool> m_save_graph;
+			data_logger & operator=(const data_logger&) = delete;
+			data_logger & operator=(data_logger&&) = delete;
+
+			void add_data(std::string filename, unsigned int data); ///< use this to append data here. Use it only the singleton. It locks itself.
+
+			static std::atomic<bool> m_save_graph; ///< global setting flag, should we save all the data or not (can disable logging graphs data)
+
 		private:
-			data_logger();
-			class fileData
-			{
+			static std::once_flag m_singleton; ///< to guarantee singleton creates the object exactly once
+			static data_logger_state m_state; ///< state of the singleton object
+			static std::atomic<bool> m_thread_maybe_running; ///< is the background thread (more or less) running, or is it fully finished
+			static std::unique_ptr<data_logger> m_obj; ///< the singleton object. Only use it via get_instance(). Can be killed by kill_instance()
+
+			/***
+			* one graph/file with data
+			*/
+			class fileData {
 				public:
-					fileData(){}
+					fileData() = default;
 					fileData(const fileData &ob) = delete;
 					fileData(std::string pFile);
 					
 					std::shared_ptr<std::ofstream> mFile;
-					long int mDataToSave = 0;
+					long int mDataToSave = 0; ///< sum of the data (in current interval, will be counted from 0 on next interval)
 					static double get_current_time();
 					void save();
 					std::string mPath;
-					bool mLimitFile = false;
+					bool mLimitFile = false; ///< this holds a number (that is not additive) - e.g. the limit setting
 			};
 			
-			std::map <std::string, fileData> mFilesMap;
-			std::mutex mSaveMutex;
-			void saveToFile();
+			std::map<std::string, fileData> mFilesMap;
+			std::mutex mMutex;
+			void saveToFile(); ///< write data to the target files. do not use this directly
 	};
 	
 } // namespace