double next_fix_fingers_date = start_time_ + PERIODIC_FIX_FINGERS_DELAY;
double next_check_predecessor_date = start_time_ + PERIODIC_CHECK_PREDECESSOR_DELAY;
double next_lookup_date = start_time_ + PERIODIC_LOOKUP_DELAY;
double next_fix_fingers_date = start_time_ + PERIODIC_FIX_FINGERS_DELAY;
double next_check_predecessor_date = start_time_ + PERIODIC_CHECK_PREDECESSOR_DELAY;
double next_lookup_date = start_time_ + PERIODIC_LOOKUP_DELAY;