Add get_server_max_lag() (#11671)

doc/lua_api.txt

@@ -5647,6 +5647,8 @@ Server
       a player joined.
     * This function may be overwritten by mods to customize the status message.
 * `minetest.get_server_uptime()`: returns the server uptime in seconds
+* `minetest.get_server_max_lag()`: returns the current maximum lag
+  of the server in seconds or nil if server is not fully loaded yet
 * `minetest.remove_player(name)`: remove player from database (if they are not
   connected).
     * As auth data is not removed, minetest.player_exists will continue to

src/script/lua_api/l_server.cpp

@@ -57,6 +57,17 @@ int ModApiServer::l_get_server_uptime(lua_State *L)
 	return 1;
 }
 
+// get_server_max_lag()
+int ModApiServer::l_get_server_max_lag(lua_State *L)
+{
+	NO_MAP_LOCK_REQUIRED;
+	ServerEnvironment *s_env = dynamic_cast<ServerEnvironment *>(getEnv(L));
+	if (!s_env)
+		lua_pushnil(L);
+	else
+		lua_pushnumber(L, s_env->getMaxLagEstimate());
+	return 1;
+}
 
 // print(text)
 int ModApiServer::l_print(lua_State *L)
@@ -512,6 +523,7 @@ void ModApiServer::Initialize(lua_State *L, int top)
 	API_FCT(request_shutdown);
 	API_FCT(get_server_status);
 	API_FCT(get_server_uptime);
+	API_FCT(get_server_max_lag);
 	API_FCT(get_worldpath);
 	API_FCT(is_singleplayer);
 

src/script/lua_api/l_server.h

@@ -33,6 +33,9 @@ private:
 	// get_server_uptime()
 	static int l_get_server_uptime(lua_State *L);
 
+	// get_server_max_lag()
+	static int l_get_server_max_lag(lua_State *L);
+
 	// get_worldpath()
 	static int l_get_worldpath(lua_State *L);