Function start_slave_threads

sql/slave.cc:1307–1390

*/

int start_slave_threads(THD *thd,
                        bool need_slave_mutex, bool wait_for_start,
                        Master_info* mi, const char* master_info_fname,
                        const char* slave_info_fname, int thread_mask)
{
  mysql_mutex_t *lock_io=0, *lock_sql=0, *lock_cond_io=0, *lock_cond_sql=0;
  mysql_cond_t* cond_io=0, *cond_sql=0;
  int error=0;
  const char *errmsg;
  DBUG_ENTER("start_slave_threads");

  if (need_slave_mutex)
  {
    lock_io = &mi->run_lock;
    lock_sql = &mi->rli.run_lock;
  }
  if (wait_for_start)
  {
    cond_io = &mi->start_cond;
    cond_sql = &mi->rli.start_cond;
    lock_cond_io = &mi->run_lock;
    lock_cond_sql = &mi->rli.run_lock;
  }

  /*
    If we are using GTID and both SQL and IO threads are stopped, then get
    rid of all relay logs.

    Relay logs are not very useful when using GTID, except as a buffer
    between the fetch in the IO thread and the apply in SQL thread. However
    while one of the threads is running, they are in use and cannot be
    removed.
  */
  if (mi->using_gtid != Master_info::USE_GTID_NO &&
      !mi->slave_running && !mi->rli.slave_running)
  {
    /*
      purge_relay_logs() clears the mi->rli.group_master_log_pos.
      So save and restore them, like we do in CHANGE MASTER.
      (We are not going to use them for GTID, but it might be worth to
      keep them in case connection with GTID fails and user wants to go
      back and continue with previous old-style replication coordinates).
    */
    mi->master_log_pos = MY_MAX(BIN_LOG_HEADER_SIZE,
                                mi->rli.group_master_log_pos);
    strmake(mi->master_log_name, mi->rli.group_master_log_name,
            sizeof(mi->master_log_name)-1);
    purge_relay_logs(&mi->rli, thd, 0, &errmsg);
    mi->rli.group_master_log_pos= mi->master_log_pos;
    strmake(mi->rli.group_master_log_name, mi->master_log_name,
            sizeof(mi->rli.group_master_log_name)-1);

    error= rpl_load_gtid_state(&mi->gtid_current_pos, mi->using_gtid ==
                                             Master_info::USE_GTID_CURRENT_POS);
    mi->events_queued_since_last_gtid= 0;
    mi->gtid_reconnect_event_skip_count= 0;

    mi->rli.restart_gtid_pos.reset();