* Added few types to make code more readable

include/MySQL_HostGroups_Manager.h

@@ -378,6 +378,25 @@ struct hg_metrics_map_idx {
 	};
 };
 
+
+/**
+ * @brief Required server info for the replication_lag Monitoring actions.
+ */
+using hostgroupid_t = int;
+using address_t = std::string;
+using port_t = unsigned int;
+using current_replication_lag = int;
+
+using replication_lag_server_t = std::tuple<hostgroupid_t,address_t,port_t,current_replication_lag>;
+
+enum REPLICATION_LAG_SERVER_T {
+	HOSTGROUP_ID = 0,
+	ADDRESS,
+	PORT,
+	CURRENT_REPLICATION_LAG,
+	__SIZE
+};
+
 class MySQL_HostGroups_Manager {
 	private:
 	SQLite3DB	*admindb;
@@ -734,7 +753,7 @@ class MySQL_HostGroups_Manager {
 	void destroy_MyConn_from_pool(MySQL_Connection *, bool _lock=true);	
 
 	void replication_lag_action_inner(MyHGC *, const char*, unsigned int, int);
-	void replication_lag_action(const std::list<std::tuple<int, std::string, unsigned int, int>>& mysql_servers);
+	void replication_lag_action(const std::list<replication_lag_server_t>& mysql_servers);
 	void read_only_action(char *hostname, int port, int read_only);
 	void read_only_action_v2(const std::list<std::tuple<std::string,int,int>>& mysql_servers);
 	unsigned int get_servers_table_version();

lib/MySQL_HostGroups_Manager.cpp

@@ -3476,22 +3476,19 @@ void MySQL_HostGroups_Manager::replication_lag_action_inner(MyHGC *myhgc, const
 	}
 }
 
-void MySQL_HostGroups_Manager::replication_lag_action(const std::list<std::tuple<int, std::string, unsigned int, int>>& mysql_servers) {
+void MySQL_HostGroups_Manager::replication_lag_action(const std::list<replication_lag_server_t>& mysql_servers) {
 
 	//this method does not use admin table, so this lock is not needed. 
 	//GloAdmin->mysql_servers_wrlock();
-
-	int hid = -1;
-	std::string address;
-	unsigned int port = 0;
-	int current_replication_lag = -1;
-
 	unsigned long long curtime1 = monotonic_time();
 	wrlock();
 
 	for (const auto& server : mysql_servers) {
 
-		std::tie(hid, address, port, current_replication_lag) = server;
+		const int hid = std::get<REPLICATION_LAG_SERVER_T::HOSTGROUP_ID>(server);
+		const std::string& address = std::get<REPLICATION_LAG_SERVER_T::ADDRESS>(server);
+		const unsigned int port = std::get<REPLICATION_LAG_SERVER_T::PORT>(server);
+		const int current_replication_lag = std::get<REPLICATION_LAG_SERVER_T::CURRENT_REPLICATION_LAG>(server);
 
 		if (mysql_thread___monitor_replication_lag_group_by_host == false) {
 			// legacy check. 1 check per server per hostgroup