#include "my_global.h" #include "rpl_parallel.h" #include "slave.h" #include "rpl_mi.h" #include "debug_sync.h" /* Code for optional parallel execution of replicated events on the slave. ToDo list: - Retry of failed transactions is not yet implemented for the parallel case. - All the waits (eg. in struct wait_for_commit and in rpl_parallel_thread_pool::get_thread()) need to be killable. And on kill, everything needs to be correctly rolled back and stopped in all threads, to ensure a consistent slave replication state. */ struct rpl_parallel_thread_pool global_rpl_thread_pool; static void signal_error_to_sql_driver_thread(THD *thd, rpl_group_info *rgi, int err); static int rpt_handle_event(rpl_parallel_thread::queued_event *qev, struct rpl_parallel_thread *rpt) { int err; rpl_group_info *rgi= qev->rgi; Relay_log_info *rli= rgi->rli; THD *thd= rgi->thd; thd->rgi_slave= rgi; thd->system_thread_info.rpl_sql_info->rpl_filter = rli->mi->rpl_filter; /* ToDo: Access to thd, and what about rli, split out a parallel part? */ mysql_mutex_lock(&rli->data_lock); qev->ev->thd= thd; strcpy(rgi->event_relay_log_name_buf, qev->event_relay_log_name); rgi->event_relay_log_name= rgi->event_relay_log_name_buf; rgi->event_relay_log_pos= qev->event_relay_log_pos; rgi->future_event_relay_log_pos= qev->future_event_relay_log_pos; strcpy(rgi->future_event_master_log_name, qev->future_event_master_log_name); err= apply_event_and_update_pos(qev->ev, thd, rgi, rpt); thd->rgi_slave= NULL; thread_safe_increment64(&rli->executed_entries, &slave_executed_entries_lock); /* ToDo: error handling. */ return err; } static void handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev) { int cmp; Relay_log_info *rli; /* Events that are not part of an event group, such as Format Description, Stop, GTID List and such, are executed directly in the driver SQL thread, to keep the relay log state up-to-date. But the associated position update is done here, in sync with other normal events as they are queued to worker threads. */ if ((thd->variables.option_bits & OPTION_BEGIN) && opt_using_transactions) return; rli= qev->rgi->rli; mysql_mutex_lock(&rli->data_lock); cmp= strcmp(rli->group_relay_log_name, qev->event_relay_log_name); if (cmp < 0) { rli->group_relay_log_pos= qev->future_event_relay_log_pos; strmake_buf(rli->group_relay_log_name, qev->event_relay_log_name); rli->notify_group_relay_log_name_update(); } else if (cmp == 0 && rli->group_relay_log_pos < qev->future_event_relay_log_pos) rli->group_relay_log_pos= qev->future_event_relay_log_pos; cmp= strcmp(rli->group_master_log_name, qev->future_event_master_log_name); if (cmp < 0) { strcpy(rli->group_master_log_name, qev->future_event_master_log_name); rli->notify_group_master_log_name_update(); rli->group_master_log_pos= qev->future_event_master_log_pos; } else if (cmp == 0 && rli->group_master_log_pos < qev->future_event_master_log_pos) rli->group_master_log_pos= qev->future_event_master_log_pos; mysql_mutex_unlock(&rli->data_lock); mysql_cond_broadcast(&rli->data_cond); } static void finish_event_group(THD *thd, uint64 sub_id, rpl_parallel_entry *entry, rpl_group_info *rgi) { wait_for_commit *wfc= &rgi->commit_orderer; int err; /* Remove any left-over registration to wait for a prior commit to complete. Normally, such wait would already have been removed at this point by wait_for_prior_commit() called from within COMMIT processing. However, in case of MyISAM and no binlog, we might not have any commit processing, and so we need to do the wait here, before waking up any subsequent commits, to preserve correct order of event execution. Also, in the error case we might have skipped waiting and thus need to remove it explicitly. It is important in the non-error case to do a wait, not just an unregister. Because we might be last in a group-commit that is replicated in parallel, and the following event will then wait for us to complete and rely on this also ensuring that any other event in the group has completed. But in the error case, we have to abort anyway, and it seems best to just complete as quickly as possible with unregister. Anyone waiting for us will in any case receive the error back from their wait_for_prior_commit() call. */ if (rgi->worker_error) wfc->unregister_wait_for_prior_commit(); else if ((err= wfc->wait_for_prior_commit(thd))) signal_error_to_sql_driver_thread(thd, rgi, err); thd->wait_for_commit_ptr= NULL; /* Record that this event group has finished (eg. transaction is committed, if transactional), so other event groups will no longer attempt to wait for us to commit. Once we have increased entry->last_committed_sub_id, no other threads will execute register_wait_for_prior_commit() against us. Thus, by doing one extra (usually redundant) wakeup_subsequent_commits() we can ensure that no register_wait_for_prior_commit() can ever happen without a subsequent wakeup_subsequent_commits() to wake it up. We can race here with the next transactions, but that is fine, as long as we check that we do not decrease last_committed_sub_id. If this commit is done, then any prior commits will also have been done and also no longer need waiting for. */ mysql_mutex_lock(&entry->LOCK_parallel_entry); if (entry->last_committed_sub_id < sub_id) entry->last_committed_sub_id= sub_id; /* If this event group got error, then any following event groups that have not yet started should just skip their group, preparing for stop of the SQL driver thread. */ if (unlikely(rgi->worker_error) && entry->stop_on_error_sub_id == (uint64)ULONGLONG_MAX) entry->stop_on_error_sub_id= sub_id; /* We need to mark that this event group started its commit phase, in case we missed it before (otherwise we would deadlock the next event group that is waiting for this). In most cases (normal DML), it will be a no-op. */ rgi->mark_start_commit_no_lock(); mysql_mutex_unlock(&entry->LOCK_parallel_entry); thd->clear_error(); thd->get_stmt_da()->reset_diagnostics_area(); wfc->wakeup_subsequent_commits(rgi->worker_error); } static void signal_error_to_sql_driver_thread(THD *thd, rpl_group_info *rgi, int err) { rgi->worker_error= err; rgi->cleanup_context(thd, true); rgi->rli->abort_slave= true; rgi->rli->stop_for_until= false; mysql_mutex_lock(rgi->rli->relay_log.get_log_lock()); mysql_mutex_unlock(rgi->rli->relay_log.get_log_lock()); rgi->rli->relay_log.signal_update(); } static void unlock_or_exit_cond(THD *thd, mysql_mutex_t *lock, bool *did_enter_cond, PSI_stage_info *old_stage) { if (*did_enter_cond) { thd->EXIT_COND(old_stage); *did_enter_cond= false; } else mysql_mutex_unlock(lock); } pthread_handler_t handle_rpl_parallel_thread(void *arg) { THD *thd; PSI_stage_info old_stage; struct rpl_parallel_thread::queued_event *events; bool group_standalone= true; bool in_event_group= false; bool skip_event_group= false; rpl_group_info *group_rgi= NULL; group_commit_orderer *gco, *tmp_gco; uint64 event_gtid_sub_id= 0; rpl_parallel_thread::queued_event *qevs_to_free; rpl_group_info *rgis_to_free; group_commit_orderer *gcos_to_free; rpl_sql_thread_info sql_info(NULL); size_t total_event_size; int err; struct rpl_parallel_thread *rpt= (struct rpl_parallel_thread *)arg; my_thread_init(); thd = new THD; thd->thread_stack = (char*)&thd; mysql_mutex_lock(&LOCK_thread_count); thd->thread_id= thd->variables.pseudo_thread_id= thread_id++; threads.append(thd); mysql_mutex_unlock(&LOCK_thread_count); set_current_thd(thd); pthread_detach_this_thread(); thd->init_for_queries(); thd->variables.binlog_annotate_row_events= 0; init_thr_lock(); thd->store_globals(); thd->system_thread= SYSTEM_THREAD_SLAVE_SQL; thd->security_ctx->skip_grants(); thd->variables.max_allowed_packet= slave_max_allowed_packet; thd->slave_thread= 1; thd->enable_slow_log= opt_log_slow_slave_statements; thd->variables.log_slow_filter= global_system_variables.log_slow_filter; set_slave_thread_options(thd); thd->client_capabilities = CLIENT_LOCAL_FILES; thd->net.reading_or_writing= 0; thd_proc_info(thd, "Waiting for work from main SQL threads"); thd->set_time(); thd->variables.lock_wait_timeout= LONG_TIMEOUT; thd->system_thread_info.rpl_sql_info= &sql_info; /* For now, we need to run the replication parallel worker threads in READ COMMITTED. This is needed because gap locks are not symmetric. For example, a gap lock from a DELETE blocks an insert intention lock, but not vice versa. So an INSERT followed by DELETE can group commit on the master, but if we are unlucky with thread scheduling we can then deadlock on the slave because the INSERT ends up waiting for a gap lock from the DELETE (and the DELETE in turn waits for the INSERT in wait_for_prior_commit()). See also MDEV-5914. It should be mostly safe to run in READ COMMITTED in the slave anyway. The commit order is already fixed from on the master, so we do not risk logging into the binlog in an incorrect order between worker threads (one that would cause different results if executed on a lower-level slave that uses this slave as a master). The only potential problem is with transactions run in a different master connection (using multi-source replication), or run directly on the slave by an application; when using READ COMMITTED we are not guaranteed serialisability of binlogged statements. In practice, this is unlikely to be an issue. In GTID mode, such parallel transactions from multi-source or application must in any case use a different replication domain, in which case binlog order by definition must be independent between the different domain. Even in non-GTID mode, normally one will assume that the external transactions are not conflicting with those applied by the slave, so that isolation level should make no difference. It would be rather strange if the result of applying query events from one master would depend on the timing and nature of other queries executed from different multi-source connections or done directly on the slave by an application. Still, something to be aware of. */ thd->variables.tx_isolation= ISO_READ_COMMITTED; mysql_mutex_lock(&rpt->LOCK_rpl_thread); rpt->thd= thd; while (rpt->delay_start) mysql_cond_wait(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread); rpt->running= true; mysql_cond_signal(&rpt->COND_rpl_thread); while (!rpt->stop) { thd->ENTER_COND(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread, &stage_waiting_for_work_from_sql_thread, &old_stage); /* There are 4 cases that should cause us to wake up: - Events have been queued for us to handle. - We have an owner, but no events and not inside event group -> we need to release ourself to the thread pool - SQL thread is stopping, and we have an owner but no events, and we are inside an event group; no more events will be queued to us, so we need to abort the group (force_abort==1). - Thread pool shutdown (rpt->stop==1). */ while (!( (events= rpt->event_queue) || (rpt->current_owner && !in_event_group) || (rpt->current_owner && group_rgi->parallel_entry->force_abort) || rpt->stop)) mysql_cond_wait(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread); rpt->dequeue1(events); thd->EXIT_COND(&old_stage); more_events: qevs_to_free= NULL; rgis_to_free= NULL; gcos_to_free= NULL; total_event_size= 0; while (events) { struct rpl_parallel_thread::queued_event *next= events->next; Log_event_type event_type; rpl_group_info *rgi= events->rgi; rpl_parallel_entry *entry= rgi->parallel_entry; bool end_of_group, group_ending; total_event_size+= events->event_size; if (!events->ev) { handle_queued_pos_update(thd, events); events->next= qevs_to_free; qevs_to_free= events; events= next; continue; } group_rgi= rgi; gco= rgi->gco; /* Handle a new event group, which will be initiated by a GTID event. */ if ((event_type= events->ev->get_type_code()) == GTID_EVENT) { bool did_enter_cond= false; PSI_stage_info old_stage; uint64 wait_count; thd->tx_isolation= (enum_tx_isolation)thd->variables.tx_isolation; in_event_group= true; /* If the standalone flag is set, then this event group consists of a single statement (possibly preceeded by some Intvar_log_event and similar), without any terminating COMMIT/ROLLBACK/XID. */ group_standalone= (0 != (static_cast(events->ev)->flags2 & Gtid_log_event::FL_STANDALONE)); /* Save this, as it gets cleared when the event group commits. */ event_gtid_sub_id= rgi->gtid_sub_id; rgi->thd= thd; /* Register ourself to wait for the previous commit, if we need to do such registration _and_ that previous commit has not already occured. Also do not start parallel execution of this event group until all prior groups have reached the commit phase that are not safe to run in parallel with. */ mysql_mutex_lock(&entry->LOCK_parallel_entry); if (!gco->installed) { if (gco->prev_gco) gco->prev_gco->next_gco= gco; gco->installed= true; } wait_count= gco->wait_count; if (wait_count > entry->count_committing_event_groups) { DEBUG_SYNC(thd, "rpl_parallel_start_waiting_for_prior"); thd->ENTER_COND(&gco->COND_group_commit_orderer, &entry->LOCK_parallel_entry, &stage_waiting_for_prior_transaction_to_commit, &old_stage); did_enter_cond= true; do { if (thd->check_killed() && !rgi->worker_error) { DEBUG_SYNC(thd, "rpl_parallel_start_waiting_for_prior_killed"); thd->send_kill_message(); slave_output_error_info(rgi->rli, thd); signal_error_to_sql_driver_thread(thd, rgi, 1); /* Even though we were killed, we need to continue waiting for the prior event groups to signal that we can continue. Otherwise we mess up the accounting for ordering. However, now that we have marked the error, events will just be skipped rather than executed, and things will progress quickly towards stop. */ } mysql_cond_wait(&gco->COND_group_commit_orderer, &entry->LOCK_parallel_entry); } while (wait_count > entry->count_committing_event_groups); } if ((tmp_gco= gco->prev_gco)) { /* Now all the event groups in the previous batch have entered their commit phase, and will no longer access their gco. So we can free it here. */ DBUG_ASSERT(!tmp_gco->prev_gco); gco->prev_gco= NULL; tmp_gco->next_gco= gcos_to_free; gcos_to_free= tmp_gco; } if (entry->force_abort && wait_count > entry->stop_count) { /* We are stopping (STOP SLAVE), and this event group is beyond the point where we can safely stop. So set a flag that will cause us to skip, rather than execute, the following events. */ skip_event_group= true; } else skip_event_group= false; if (unlikely(entry->stop_on_error_sub_id <= rgi->wait_commit_sub_id)) skip_event_group= true; else if (rgi->wait_commit_sub_id > entry->last_committed_sub_id) { /* Register that the commit of this event group must wait for the commit of the previous event group to complete before it may complete itself, so that we preserve commit order. */ wait_for_commit *waitee= &rgi->wait_commit_group_info->commit_orderer; rgi->commit_orderer.register_wait_for_prior_commit(waitee); } unlock_or_exit_cond(thd, &entry->LOCK_parallel_entry, &did_enter_cond, &old_stage); if(thd->wait_for_commit_ptr) { /* This indicates that we get a new GTID event in the middle of a not completed event group. This is corrupt binlog (the master will never write such binlog), so it does not happen unless someone tries to inject wrong crafted binlog, but let us still try to handle it somewhat nicely. */ rgi->cleanup_context(thd, true); thd->wait_for_commit_ptr->unregister_wait_for_prior_commit(); thd->wait_for_commit_ptr->wakeup_subsequent_commits(rgi->worker_error); } thd->wait_for_commit_ptr= &rgi->commit_orderer; if (opt_gtid_ignore_duplicates) { int res= rpl_global_gtid_slave_state.check_duplicate_gtid(&rgi->current_gtid, rgi); if (res < 0) { /* Error. */ slave_output_error_info(rgi->rli, thd); signal_error_to_sql_driver_thread(thd, rgi, 1); } else if (!res) { /* GTID already applied by another master connection, skip. */ skip_event_group= true; } else { /* We have to apply the event. */ } } } group_ending= event_type == XID_EVENT || (event_type == QUERY_EVENT && (((Query_log_event *)events->ev)->is_commit() || ((Query_log_event *)events->ev)->is_rollback())); if (group_ending) { DEBUG_SYNC(thd, "rpl_parallel_before_mark_start_commit"); rgi->mark_start_commit(); } /* If the SQL thread is stopping, we just skip execution of all the following event groups. We still do all the normal waiting and wakeup processing between the event groups as a simple way to ensure that everything is stopped and cleaned up correctly. */ if (!rgi->worker_error && !skip_event_group) err= rpt_handle_event(events, rpt); else err= thd->wait_for_prior_commit(); end_of_group= in_event_group && ((group_standalone && !Log_event::is_part_of_group(event_type)) || group_ending); delete_or_keep_event_post_apply(rgi, event_type, events->ev); events->next= qevs_to_free; qevs_to_free= events; if (unlikely(err) && !rgi->worker_error) { slave_output_error_info(rgi->rli, thd); signal_error_to_sql_driver_thread(thd, rgi, err); } if (end_of_group) { in_event_group= false; finish_event_group(thd, event_gtid_sub_id, entry, rgi); rgi->next= rgis_to_free; rgis_to_free= rgi; group_rgi= rgi= NULL; skip_event_group= false; DEBUG_SYNC(thd, "rpl_parallel_end_of_group"); } events= next; } mysql_mutex_lock(&rpt->LOCK_rpl_thread); /* Signal that our queue can now accept more events. */ rpt->dequeue2(total_event_size); mysql_cond_signal(&rpt->COND_rpl_thread_queue); /* We need to delay the free here, to when we have the lock. */ while (gcos_to_free) { group_commit_orderer *next= gcos_to_free->next_gco; rpt->free_gco(gcos_to_free); gcos_to_free= next; } while (rgis_to_free) { rpl_group_info *next= rgis_to_free->next; rpt->free_rgi(rgis_to_free); rgis_to_free= next; } while (qevs_to_free) { rpl_parallel_thread::queued_event *next= qevs_to_free->next; rpt->free_qev(qevs_to_free); qevs_to_free= next; } if ((events= rpt->event_queue) != NULL) { /* Take next group of events from the replication pool. This is faster than having to wakeup the pool manager thread to give us a new event. */ rpt->dequeue1(events); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); goto more_events; } if (in_event_group && group_rgi->parallel_entry->force_abort) { /* We are asked to abort, without getting the remaining events in the current event group. We have to rollback the current transaction and update the last sub_id value so that SQL thread will know we are done with the half-processed event group. */ mysql_mutex_unlock(&rpt->LOCK_rpl_thread); signal_error_to_sql_driver_thread(thd, group_rgi, 1); finish_event_group(thd, group_rgi->gtid_sub_id, group_rgi->parallel_entry, group_rgi); in_event_group= false; mysql_mutex_lock(&rpt->LOCK_rpl_thread); rpt->free_rgi(group_rgi); group_rgi= NULL; skip_event_group= false; } if (!in_event_group) { rpt->current_owner= NULL; /* Tell wait_for_done() that we are done, if it is waiting. */ if (likely(rpt->current_entry) && unlikely(rpt->current_entry->force_abort)) mysql_cond_broadcast(&rpt->current_entry->COND_parallel_entry); rpt->current_entry= NULL; if (!rpt->stop) rpt->pool->release_thread(rpt); } } rpt->thd= NULL; mysql_mutex_unlock(&rpt->LOCK_rpl_thread); thd->clear_error(); thd->catalog= 0; thd->reset_query(); thd->reset_db(NULL, 0); thd_proc_info(thd, "Slave worker thread exiting"); thd->temporary_tables= 0; mysql_mutex_lock(&LOCK_thread_count); THD_CHECK_SENTRY(thd); delete thd; mysql_mutex_unlock(&LOCK_thread_count); mysql_mutex_lock(&rpt->LOCK_rpl_thread); rpt->running= false; mysql_cond_signal(&rpt->COND_rpl_thread); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); my_thread_end(); return NULL; } static void dealloc_gco(group_commit_orderer *gco) { DBUG_ASSERT(!gco->prev_gco /* Must only free after dealloc previous */); mysql_cond_destroy(&gco->COND_group_commit_orderer); my_free(gco); } int rpl_parallel_change_thread_count(rpl_parallel_thread_pool *pool, uint32 new_count, bool skip_check) { uint32 i; rpl_parallel_thread **new_list= NULL; rpl_parallel_thread *new_free_list= NULL; rpl_parallel_thread *rpt_array= NULL; /* Allocate the new list of threads up-front. That way, if we fail half-way, we only need to free whatever we managed to allocate, and will not be left with a half-functional thread pool. */ if (new_count && !my_multi_malloc(MYF(MY_WME|MY_ZEROFILL), &new_list, new_count*sizeof(*new_list), &rpt_array, new_count*sizeof(*rpt_array), NULL)) { my_error(ER_OUTOFMEMORY, MYF(0), (int(new_count*sizeof(*new_list) + new_count*sizeof(*rpt_array)))); goto err;; } for (i= 0; i < new_count; ++i) { pthread_t th; new_list[i]= &rpt_array[i]; new_list[i]->delay_start= true; mysql_mutex_init(key_LOCK_rpl_thread, &new_list[i]->LOCK_rpl_thread, MY_MUTEX_INIT_SLOW); mysql_cond_init(key_COND_rpl_thread, &new_list[i]->COND_rpl_thread, NULL); mysql_cond_init(key_COND_rpl_thread_queue, &new_list[i]->COND_rpl_thread_queue, NULL); new_list[i]->pool= pool; if (mysql_thread_create(key_rpl_parallel_thread, &th, &connection_attrib, handle_rpl_parallel_thread, new_list[i])) { my_error(ER_OUT_OF_RESOURCES, MYF(0)); goto err; } new_list[i]->next= new_free_list; new_free_list= new_list[i]; } if (!skip_check) { mysql_mutex_lock(&LOCK_active_mi); if (master_info_index->give_error_if_slave_running()) { mysql_mutex_unlock(&LOCK_active_mi); goto err; } if (pool->changing) { mysql_mutex_unlock(&LOCK_active_mi); my_error(ER_CHANGE_SLAVE_PARALLEL_THREADS_ACTIVE, MYF(0)); goto err; } pool->changing= true; mysql_mutex_unlock(&LOCK_active_mi); } /* Grab each old thread in turn, and signal it to stop. Note that since we require all replication threads to be stopped before changing the parallel replication worker thread pool, all the threads will be already idle and will terminate immediately. */ for (i= 0; i < pool->count; ++i) { rpl_parallel_thread *rpt= pool->get_thread(NULL, NULL); rpt->stop= true; mysql_cond_signal(&rpt->COND_rpl_thread); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); } for (i= 0; i < pool->count; ++i) { rpl_parallel_thread *rpt= pool->threads[i]; mysql_mutex_lock(&rpt->LOCK_rpl_thread); while (rpt->running) mysql_cond_wait(&rpt->COND_rpl_thread, &rpt->LOCK_rpl_thread); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); mysql_mutex_destroy(&rpt->LOCK_rpl_thread); mysql_cond_destroy(&rpt->COND_rpl_thread); while (rpt->qev_free_list) { rpl_parallel_thread::queued_event *next= rpt->qev_free_list->next; my_free(rpt->qev_free_list); rpt->qev_free_list= next; } while (rpt->rgi_free_list) { rpl_group_info *next= rpt->rgi_free_list->next; delete rpt->rgi_free_list; rpt->rgi_free_list= next; } while (rpt->gco_free_list) { group_commit_orderer *next= rpt->gco_free_list->next_gco; dealloc_gco(rpt->gco_free_list); rpt->gco_free_list= next; } } my_free(pool->threads); pool->threads= new_list; pool->free_list= new_free_list; pool->count= new_count; for (i= 0; i < pool->count; ++i) { mysql_mutex_lock(&pool->threads[i]->LOCK_rpl_thread); pool->threads[i]->delay_start= false; mysql_cond_signal(&pool->threads[i]->COND_rpl_thread); while (!pool->threads[i]->running) mysql_cond_wait(&pool->threads[i]->COND_rpl_thread, &pool->threads[i]->LOCK_rpl_thread); mysql_mutex_unlock(&pool->threads[i]->LOCK_rpl_thread); } if (!skip_check) { mysql_mutex_lock(&LOCK_active_mi); pool->changing= false; mysql_mutex_unlock(&LOCK_active_mi); } mysql_mutex_lock(&pool->LOCK_rpl_thread_pool); mysql_cond_broadcast(&pool->COND_rpl_thread_pool); mysql_mutex_unlock(&pool->LOCK_rpl_thread_pool); return 0; err: if (new_list) { while (new_free_list) { mysql_mutex_lock(&new_free_list->LOCK_rpl_thread); new_free_list->delay_start= false; new_free_list->stop= true; mysql_cond_signal(&new_free_list->COND_rpl_thread); while (!new_free_list->running) mysql_cond_wait(&new_free_list->COND_rpl_thread, &new_free_list->LOCK_rpl_thread); while (new_free_list->running) mysql_cond_wait(&new_free_list->COND_rpl_thread, &new_free_list->LOCK_rpl_thread); mysql_mutex_unlock(&new_free_list->LOCK_rpl_thread); new_free_list= new_free_list->next; } my_free(new_list); } if (!skip_check) { mysql_mutex_lock(&LOCK_active_mi); pool->changing= false; mysql_mutex_unlock(&LOCK_active_mi); } return 1; } rpl_parallel_thread::queued_event * rpl_parallel_thread::get_qev(Log_event *ev, ulonglong event_size, Relay_log_info *rli) { queued_event *qev; mysql_mutex_assert_owner(&LOCK_rpl_thread); if ((qev= qev_free_list)) qev_free_list= qev->next; else if(!(qev= (queued_event *)my_malloc(sizeof(*qev), MYF(0)))) { my_error(ER_OUTOFMEMORY, MYF(0), (int)sizeof(*qev)); return NULL; } qev->ev= ev; qev->event_size= event_size; qev->next= NULL; strcpy(qev->event_relay_log_name, rli->event_relay_log_name); qev->event_relay_log_pos= rli->event_relay_log_pos; qev->future_event_relay_log_pos= rli->future_event_relay_log_pos; strcpy(qev->future_event_master_log_name, rli->future_event_master_log_name); return qev; } void rpl_parallel_thread::free_qev(rpl_parallel_thread::queued_event *qev) { mysql_mutex_assert_owner(&LOCK_rpl_thread); qev->next= qev_free_list; qev_free_list= qev; } rpl_group_info* rpl_parallel_thread::get_rgi(Relay_log_info *rli, Gtid_log_event *gtid_ev, rpl_parallel_entry *e) { rpl_group_info *rgi; mysql_mutex_assert_owner(&LOCK_rpl_thread); if ((rgi= rgi_free_list)) { rgi_free_list= rgi->next; rgi->reinit(rli); } else { if(!(rgi= new rpl_group_info(rli))) { my_error(ER_OUTOFMEMORY, MYF(0), (int)sizeof(*rgi)); return NULL; } rgi->is_parallel_exec = true; } if ((rgi->deferred_events_collecting= rli->mi->rpl_filter->is_on()) && !rgi->deferred_events) rgi->deferred_events= new Deferred_log_events(rli); if (event_group_new_gtid(rgi, gtid_ev)) { free_rgi(rgi); my_error(ER_OUT_OF_RESOURCES, MYF(MY_WME)); return NULL; } rgi->parallel_entry= e; return rgi; } void rpl_parallel_thread::free_rgi(rpl_group_info *rgi) { mysql_mutex_assert_owner(&LOCK_rpl_thread); DBUG_ASSERT(rgi->commit_orderer.waitee == NULL); rgi->free_annotate_event(); rgi->next= rgi_free_list; rgi_free_list= rgi; } group_commit_orderer * rpl_parallel_thread::get_gco(uint64 wait_count, group_commit_orderer *prev) { group_commit_orderer *gco; mysql_mutex_assert_owner(&LOCK_rpl_thread); if ((gco= gco_free_list)) gco_free_list= gco->next_gco; else if(!(gco= (group_commit_orderer *)my_malloc(sizeof(*gco), MYF(0)))) { my_error(ER_OUTOFMEMORY, MYF(0), (int)sizeof(*gco)); return NULL; } mysql_cond_init(key_COND_group_commit_orderer, &gco->COND_group_commit_orderer, NULL); gco->wait_count= wait_count; gco->prev_gco= prev; gco->next_gco= NULL; gco->installed= false; return gco; } void rpl_parallel_thread::free_gco(group_commit_orderer *gco) { mysql_mutex_assert_owner(&LOCK_rpl_thread); DBUG_ASSERT(!gco->prev_gco /* Must not free until wait has completed. */); gco->next_gco= gco_free_list; gco_free_list= gco; } rpl_parallel_thread_pool::rpl_parallel_thread_pool() : count(0), threads(0), free_list(0), changing(false), inited(false) { } int rpl_parallel_thread_pool::init(uint32 size) { count= 0; threads= NULL; free_list= NULL; mysql_mutex_init(key_LOCK_rpl_thread_pool, &LOCK_rpl_thread_pool, MY_MUTEX_INIT_SLOW); mysql_cond_init(key_COND_rpl_thread_pool, &COND_rpl_thread_pool, NULL); changing= false; inited= true; return rpl_parallel_change_thread_count(this, size, true); } void rpl_parallel_thread_pool::destroy() { if (!inited) return; rpl_parallel_change_thread_count(this, 0, true); mysql_mutex_destroy(&LOCK_rpl_thread_pool); mysql_cond_destroy(&COND_rpl_thread_pool); inited= false; } /* Wait for a worker thread to become idle. When one does, grab the thread for our use and return it. Note that we return with the worker threads's LOCK_rpl_thread mutex locked. */ struct rpl_parallel_thread * rpl_parallel_thread_pool::get_thread(rpl_parallel_thread **owner, rpl_parallel_entry *entry) { rpl_parallel_thread *rpt; mysql_mutex_lock(&LOCK_rpl_thread_pool); while ((rpt= free_list) == NULL) mysql_cond_wait(&COND_rpl_thread_pool, &LOCK_rpl_thread_pool); free_list= rpt->next; mysql_mutex_unlock(&LOCK_rpl_thread_pool); mysql_mutex_lock(&rpt->LOCK_rpl_thread); rpt->current_owner= owner; rpt->current_entry= entry; return rpt; } /* Release a thread to the thread pool. The thread should be locked, and should not have any work queued for it. */ void rpl_parallel_thread_pool::release_thread(rpl_parallel_thread *rpt) { rpl_parallel_thread *list; mysql_mutex_assert_owner(&rpt->LOCK_rpl_thread); DBUG_ASSERT(rpt->current_owner == NULL); mysql_mutex_lock(&LOCK_rpl_thread_pool); list= free_list; rpt->next= list; free_list= rpt; if (!list) mysql_cond_broadcast(&COND_rpl_thread_pool); mysql_mutex_unlock(&LOCK_rpl_thread_pool); } /* Obtain a worker thread that we can queue an event to. Each invocation allocates a new worker thread, to maximise parallelism. However, only up to a maximum of --slave-domain-parallel-threads workers can be occupied by a single replication domain; after that point, we start re-using worker threads that are still executing events that were queued earlier for this thread. We never queue more than --rpl-parallel-wait-queue_max amount of events for one worker, to avoid the SQL driver thread using up all memory with queued events while worker threads are stalling. Note that this function returns with rpl_parallel_thread::LOCK_rpl_thread locked. Exception is if we were killed, in which case NULL is returned. The *did_enter_cond flag is set true if we had to wait for a worker thread to become free (with mysql_cond_wait()). If so, old_stage will also be set, and the LOCK_rpl_thread must be released with THD::EXIT_COND() instead of mysql_mutex_unlock. If the flag `reuse' is set, the last worker thread will be returned again, if it is still available. Otherwise a new worker thread is allocated. */ rpl_parallel_thread * rpl_parallel_entry::choose_thread(Relay_log_info *rli, bool *did_enter_cond, PSI_stage_info *old_stage, bool reuse) { uint32 idx; rpl_parallel_thread *thr; idx= rpl_thread_idx; if (!reuse) { ++idx; if (idx >= rpl_thread_max) idx= 0; rpl_thread_idx= idx; } thr= rpl_threads[idx]; if (thr) { *did_enter_cond= false; mysql_mutex_lock(&thr->LOCK_rpl_thread); for (;;) { if (thr->current_owner != &rpl_threads[idx]) { /* The worker thread became idle, and returned to the free list and possibly was allocated to a different request. So we should allocate a new worker thread. */ unlock_or_exit_cond(rli->sql_driver_thd, &thr->LOCK_rpl_thread, did_enter_cond, old_stage); thr= NULL; break; } else if (thr->queued_size <= opt_slave_parallel_max_queued) { /* The thread is ready to queue into. */ break; } else if (rli->sql_driver_thd->check_killed()) { unlock_or_exit_cond(rli->sql_driver_thd, &thr->LOCK_rpl_thread, did_enter_cond, old_stage); my_error(ER_CONNECTION_KILLED, MYF(0)); DBUG_EXECUTE_IF("rpl_parallel_wait_queue_max", { debug_sync_set_action(rli->sql_driver_thd, STRING_WITH_LEN("now SIGNAL wait_queue_killed")); };); slave_output_error_info(rli, rli->sql_driver_thd); return NULL; } else { /* We have reached the limit of how much memory we are allowed to use for queuing events, so wait for the thread to consume some of its queue. */ if (!*did_enter_cond) { /* We need to do the debug_sync before ENTER_COND(). Because debug_sync changes the thd->mysys_var->current_mutex, and this can cause THD::awake to use the wrong mutex. */ DBUG_EXECUTE_IF("rpl_parallel_wait_queue_max", { debug_sync_set_action(rli->sql_driver_thd, STRING_WITH_LEN("now SIGNAL wait_queue_ready")); };); rli->sql_driver_thd->ENTER_COND(&thr->COND_rpl_thread_queue, &thr->LOCK_rpl_thread, &stage_waiting_for_room_in_worker_thread, old_stage); *did_enter_cond= true; } mysql_cond_wait(&thr->COND_rpl_thread_queue, &thr->LOCK_rpl_thread); } } } if (!thr) rpl_threads[idx]= thr= global_rpl_thread_pool.get_thread(&rpl_threads[idx], this); return thr; } static void free_rpl_parallel_entry(void *element) { rpl_parallel_entry *e= (rpl_parallel_entry *)element; if (e->current_gco) dealloc_gco(e->current_gco); mysql_cond_destroy(&e->COND_parallel_entry); mysql_mutex_destroy(&e->LOCK_parallel_entry); my_free(e); } rpl_parallel::rpl_parallel() : current(NULL), sql_thread_stopping(false) { my_hash_init(&domain_hash, &my_charset_bin, 32, offsetof(rpl_parallel_entry, domain_id), sizeof(uint32), NULL, free_rpl_parallel_entry, HASH_UNIQUE); } void rpl_parallel::reset() { my_hash_reset(&domain_hash); current= NULL; sql_thread_stopping= false; } rpl_parallel::~rpl_parallel() { my_hash_free(&domain_hash); } rpl_parallel_entry * rpl_parallel::find(uint32 domain_id) { struct rpl_parallel_entry *e; if (!(e= (rpl_parallel_entry *)my_hash_search(&domain_hash, (const uchar *)&domain_id, 0))) { /* Allocate a new, empty one. */ ulong count= opt_slave_domain_parallel_threads; if (count == 0 || count > opt_slave_parallel_threads) count= opt_slave_parallel_threads; rpl_parallel_thread **p; if (!my_multi_malloc(MYF(MY_WME|MY_ZEROFILL), &e, sizeof(*e), &p, count*sizeof(*p), NULL)) { my_error(ER_OUTOFMEMORY, MYF(0), (int)(sizeof(*e)+count*sizeof(*p))); return NULL; } e->rpl_threads= p; e->rpl_thread_max= count; e->domain_id= domain_id; e->stop_on_error_sub_id= (uint64)ULONGLONG_MAX; if (my_hash_insert(&domain_hash, (uchar *)e)) { my_free(e); return NULL; } mysql_mutex_init(key_LOCK_parallel_entry, &e->LOCK_parallel_entry, MY_MUTEX_INIT_FAST); mysql_cond_init(key_COND_parallel_entry, &e->COND_parallel_entry, NULL); } else e->force_abort= false; return e; } void rpl_parallel::wait_for_done(THD *thd, Relay_log_info *rli) { struct rpl_parallel_entry *e; rpl_parallel_thread *rpt; uint32 i, j; /* First signal all workers that they must force quit; no more events will be queued to complete any partial event groups executed. */ for (i= 0; i < domain_hash.records; ++i) { e= (struct rpl_parallel_entry *)my_hash_element(&domain_hash, i); mysql_mutex_lock(&e->LOCK_parallel_entry); /* We want the worker threads to stop as quickly as is safe. If the slave SQL threads are behind, we could have significant amount of events queued for the workers, and we want to stop without waiting for them all to be applied first. But if any event group has already started executing in a worker, we want to be sure that all prior event groups are also executed, so that we stop at a consistent point in the binlog stream (per replication domain). All event groups wait for e->count_committing_event_groups to reach the value of group_commit_orderer::wait_count before starting to execute. Thus, at this point we know that any event group with a strictly larger wait_count are safe to skip, none of them can have started executing yet. So we set e->stop_count here and use it to decide in the worker threads whether to continue executing an event group or whether to skip it, when force_abort is set. If we stop due to reaching the START SLAVE UNTIL condition, then we need to continue executing any queued events up to that point. */ e->force_abort= true; e->stop_count= rli->stop_for_until ? e->count_queued_event_groups : e->count_committing_event_groups; mysql_mutex_unlock(&e->LOCK_parallel_entry); for (j= 0; j < e->rpl_thread_max; ++j) { if ((rpt= e->rpl_threads[j])) { mysql_mutex_lock(&rpt->LOCK_rpl_thread); if (rpt->current_owner == &e->rpl_threads[j]) mysql_cond_signal(&rpt->COND_rpl_thread); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); } } } DBUG_EXECUTE_IF("rpl_parallel_wait_for_done_trigger", { debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL wait_for_done_waiting")); };); for (i= 0; i < domain_hash.records; ++i) { e= (struct rpl_parallel_entry *)my_hash_element(&domain_hash, i); for (j= 0; j < e->rpl_thread_max; ++j) { if ((rpt= e->rpl_threads[j])) { mysql_mutex_lock(&rpt->LOCK_rpl_thread); while (rpt->current_owner == &e->rpl_threads[j]) mysql_cond_wait(&e->COND_parallel_entry, &rpt->LOCK_rpl_thread); mysql_mutex_unlock(&rpt->LOCK_rpl_thread); } } } } /* This function handles the case where the SQL driver thread reached the START SLAVE UNTIL position; we stop queueing more events but continue processing remaining, already queued events; then use executes manual STOP SLAVE; then this function signals to worker threads that they should stop the processing of any remaining queued events. */ void rpl_parallel::stop_during_until() { struct rpl_parallel_entry *e; uint32 i; for (i= 0; i < domain_hash.records; ++i) { e= (struct rpl_parallel_entry *)my_hash_element(&domain_hash, i); mysql_mutex_lock(&e->LOCK_parallel_entry); if (e->force_abort) e->stop_count= e->count_committing_event_groups; mysql_mutex_unlock(&e->LOCK_parallel_entry); } } bool rpl_parallel::workers_idle() { struct rpl_parallel_entry *e; uint32 i, max_i; max_i= domain_hash.records; for (i= 0; i < max_i; ++i) { bool active; e= (struct rpl_parallel_entry *)my_hash_element(&domain_hash, i); mysql_mutex_lock(&e->LOCK_parallel_entry); active= e->current_sub_id > e->last_committed_sub_id; mysql_mutex_unlock(&e->LOCK_parallel_entry); if (active) break; } return (i == max_i); } /* This is used when we get an error during processing in do_event(); We will not queue any event to the thread, but we still need to wake it up to be sure that it will be returned to the pool. */ static void abandon_worker_thread(THD *thd, rpl_parallel_thread *cur_thread, bool *did_enter_cond, PSI_stage_info *old_stage) { unlock_or_exit_cond(thd, &cur_thread->LOCK_rpl_thread, did_enter_cond, old_stage); mysql_cond_signal(&cur_thread->COND_rpl_thread); } /* do_event() is executed by the sql_driver_thd thread. It's main purpose is to find a thread that can execute the query. @retval 0 ok, event was accepted @retval 1 error @retval -1 event should be executed serially, in the sql driver thread */ int rpl_parallel::do_event(rpl_group_info *serial_rgi, Log_event *ev, ulonglong event_size) { rpl_parallel_entry *e; rpl_parallel_thread *cur_thread; rpl_parallel_thread::queued_event *qev; rpl_group_info *rgi= NULL; Relay_log_info *rli= serial_rgi->rli; enum Log_event_type typ; bool is_group_event; bool did_enter_cond= false; PSI_stage_info old_stage; /* Handle master log name change, seen in Rotate_log_event. */ typ= ev->get_type_code(); if (unlikely(typ == ROTATE_EVENT)) { Rotate_log_event *rev= static_cast(ev); if ((rev->server_id != global_system_variables.server_id || rli->replicate_same_server_id) && !rev->is_relay_log_event() && !rli->is_in_group()) { memcpy(rli->future_event_master_log_name, rev->new_log_ident, rev->ident_len+1); } } /* Execute queries non-parallel if slave_skip_counter is set, as it's is easier to skip queries in single threaded mode. */ if (rli->slave_skip_counter) return -1; /* Execute pre-10.0 event, which have no GTID, in single-threaded mode. */ if (unlikely(!current) && typ != GTID_EVENT) return -1; /* ToDo: what to do with this lock?!? */ mysql_mutex_unlock(&rli->data_lock); /* Stop queueing additional event groups once the SQL thread is requested to stop. We have to queue any remaining events of any event group that has already been partially queued, but after that we will just ignore any further events the SQL driver thread may try to queue, and eventually it will stop. */ is_group_event= Log_event::is_group_event(typ); if ((typ == GTID_EVENT || !is_group_event) && rli->abort_slave) sql_thread_stopping= true; if (sql_thread_stopping) { delete ev; /* Return "no error"; normal stop is not an error, and otherwise the error has already been recorded. */ return 0; } if (typ == GTID_EVENT) { uint32 domain_id; if (likely(typ == GTID_EVENT)) { Gtid_log_event *gtid_ev= static_cast(ev); domain_id= (rli->mi->using_gtid == Master_info::USE_GTID_NO ? 0 : gtid_ev->domain_id); } else domain_id= 0; if (!(e= find(domain_id))) { my_error(ER_OUT_OF_RESOURCES, MYF(MY_WME)); delete ev; return 1; } current= e; } else e= current; /* Find a worker thread to queue the event for. Prefer a new thread, so we maximise parallelism (at least for the group commit). But do not exceed a limit of --slave-domain-parallel-threads; instead re-use a thread that we queued for previously. */ cur_thread= e->choose_thread(rli, &did_enter_cond, &old_stage, typ != GTID_EVENT); if (!cur_thread) { /* This means we were killed. The error is already signalled. */ delete ev; return 1; } if (!(qev= cur_thread->get_qev(ev, event_size, rli))) { abandon_worker_thread(rli->sql_driver_thd, cur_thread, &did_enter_cond, &old_stage); delete ev; return 1; } if (typ == GTID_EVENT) { Gtid_log_event *gtid_ev= static_cast(ev); if (!(rgi= cur_thread->get_rgi(rli, gtid_ev, e))) { cur_thread->free_qev(qev); abandon_worker_thread(rli->sql_driver_thd, cur_thread, &did_enter_cond, &old_stage); delete ev; return 1; } /* We queue the event group in a new worker thread, to run in parallel with previous groups. To preserve commit order within the replication domain, we set up rgi->wait_commit_sub_id to make the new group commit only after the previous group has committed. Event groups that group-committed together on the master can be run in parallel with each other without restrictions. But one batch of group-commits may not start before all groups in the previous batch have initiated their commit phase; we set up rgi->gco to ensure that. */ rgi->wait_commit_sub_id= e->current_sub_id; rgi->wait_commit_group_info= e->current_group_info; if (!((gtid_ev->flags2 & Gtid_log_event::FL_GROUP_COMMIT_ID) && e->last_commit_id == gtid_ev->commit_id)) { /* A new batch of transactions that group-committed together on the master. Remember the count that marks the end of the previous group committed batch, and allocate a new gco. */ uint64 count= e->count_queued_event_groups; group_commit_orderer *gco; if (!(gco= cur_thread->get_gco(count, e->current_gco))) { cur_thread->free_rgi(rgi); cur_thread->free_qev(qev); abandon_worker_thread(rli->sql_driver_thd, cur_thread, &did_enter_cond, &old_stage); delete ev; return 1; } e->current_gco= rgi->gco= gco; } else rgi->gco= e->current_gco; if (gtid_ev->flags2 & Gtid_log_event::FL_GROUP_COMMIT_ID) e->last_commit_id= gtid_ev->commit_id; else e->last_commit_id= 0; qev->rgi= e->current_group_info= rgi; e->current_sub_id= rgi->gtid_sub_id; ++e->count_queued_event_groups; } else if (!is_group_event) { int err; bool tmp; /* Events like ROTATE and FORMAT_DESCRIPTION. Do not run in worker thread. Same for events not preceeded by GTID (we should not see those normally, but they might be from an old master). */ qev->rgi= serial_rgi; tmp= serial_rgi->is_parallel_exec; serial_rgi->is_parallel_exec= true; err= rpt_handle_event(qev, NULL); serial_rgi->is_parallel_exec= tmp; if (ev->is_relay_log_event()) qev->future_event_master_log_pos= 0; else if (typ == ROTATE_EVENT) qev->future_event_master_log_pos= (static_cast(ev))->pos; else qev->future_event_master_log_pos= ev->log_pos; delete_or_keep_event_post_apply(serial_rgi, typ, ev); if (err) { cur_thread->free_qev(qev); abandon_worker_thread(rli->sql_driver_thd, cur_thread, &did_enter_cond, &old_stage); return 1; } /* Queue an empty event, so that the position will be updated in a reasonable way relative to other events: - If the currently executing events are queued serially for a single thread, the position will only be updated when everything before has completed. - If we are executing multiple independent events in parallel, then at least the position will not be updated until one of them has reached the current point. */ qev->ev= NULL; } else { qev->rgi= e->current_group_info; } /* Queue the event for processing. */ rli->event_relay_log_pos= rli->future_event_relay_log_pos; cur_thread->enqueue(qev); unlock_or_exit_cond(rli->sql_driver_thd, &cur_thread->LOCK_rpl_thread, &did_enter_cond, &old_stage); mysql_cond_signal(&cur_thread->COND_rpl_thread); return 0; }