===================================MySQL5.7 mysqld_main() |-init_slave() |-int thread_mask= SLAVE_SQL | SLAVE_IO; //Create slave info objects by reading repositories of individual channels and add them into channel_map |-Rpl_info_factory::create_slave_info_objects(opt_mi_repository_id,opt_rli_repository_id,thread_mask,&channel_map))) |-check_slave_sql_config_conflict() //Check if there is any slave SQL config conflict. |-if (!opt_skip_slave_start) //如果配置了skip-slave-start，则不会走下面逻辑去启动IO线程和SQL线程 //Loop through the channel_map and start slave threads for each channel. |-for (mi_map::iterator it= channel_map.begin(); it!=channel_map.end(); it++) |-start_slave_threads() |-if (thread_mask & SLAVE_IO) |-is_error=start_slave_thread(…,handle_slave_io,…) |-if (!is_error && (thread_mask & SLAVE_SQL)) //MTS-recovery gaps gathering is placed onto common execution path for either START-SLAVE and –skip-start-slave= 0 |-if (mi->rli->recovery_parallel_workers != 0) if (mts_recovery_groups(mi->rli)) |-is_error= true; |-if (!is_error) |-start_slave_thread(…,handle_slave_sql,…)

mts_recovery_groups() |-