ORACLE 中的SHUTDOWN
MySQL SHUTDOWN LEVEL 暂时只有一种，源码中留了 LEVEL 的坑还没填
在此借用 Oracle 的 SHUTDOWN LEVEL 分析
Oracle SHUTDOWN LEVEL 共有四种：ABORT、IMMEDIATE、NORMAL、TRANSACTIONAL
ABORT
- 立即结束所有SQL
- 回滚未提交事务
- 断开所有用户连接
- 下次启动实例时，需要recovery
IMMEDIATE
- 允许正在运行的SQL执行完毕
- 回滚未提交事务
- 断开所有用户连接
NORMAL
- 不允许建立新连接
- 等待当前连接断开
- 下次启动实例时，不需要recovery
TRANSACTIONAL
- 等待事务提交或结束
- 不允许新建连接
- 事务提交或结束后断开连接
MySQL 中的 SHUTDOWN 实际相当于 Oracle 中的 SHUTDOWN IMMEDIATE，重启实例时无需recovery，但回滚事务的过程可能耗时很长
MySQL SHUTDOWN过程分析
- mysql_shutdown 发送SHUTDOWN命令
- dispatch_command() 接受到 COM_SHUTDOWN command，调用kill_mysql()
- kill_mysql()创建 kill_server_thread
- kill_server_thread 调用 kill_server()
- kill_server()
- close_connections()
- 关闭端口
- 断开连接
- 回滚事务（可能耗时很长）
- unireg_end
- clean_up innobase_shutdown_for_mysql
- delete_pid_file
InnoDB shutdown 速度取决于参数 innodb_fast_shutdown
0: 最慢，需等待purge完成，change buffer merge完成1: default， 不需要等待purge完成和change buffer merge完成
2: 不等待后台删除表完成，row_drop_tables_for_mysql_in_background 不等刷脏页，如果设置了innodb_buffer_pool_dump_at_shutdown，不需要去buffer dump.
case COM_SHUTDOWN: // 接受到SHUTDOWN命令 { if (packet_length < 1) { my_error(ER_MALFORMED_PACKET, MYF(0)); break; } status_var_increment(thd->status_var.com_other); if (check_global_access(thd,SHUTDOWN_ACL)) // 检查权限 break; /* purecov: inspected */ /* If the client is < 4.1.3, it is going to send us no argument; then packet_length is 0, packet[0] is the end 0 of the packet. Note that SHUTDOWN_DEFAULT is 0. If client is >= 4.1.3, the shutdown level is in packet[0]. */ enum mysql_enum_shutdown_level level; // 留的坑，default以外的LEVEL都没实现 if (!thd->is_valid_time()) level= SHUTDOWN_DEFAULT; else level= (enum mysql_enum_shutdown_level) (uchar) packet[0]; if (level == SHUTDOWN_DEFAULT) level= SHUTDOWN_WAIT_ALL_BUFFERS; // soon default will be configurable else if (level != SHUTDOWN_WAIT_ALL_BUFFERS) { my_error(ER_NOT_SUPPORTED_YET, MYF(0), "this shutdown level"); break; } DBUG_PRINT("quit",("Got shutdown command for level %u", level)); general_log_print(thd, command, NullS); // 记录general_log my_eof(thd); kill_mysql(); // 调用kill_mysql()函数，函数内部创建 kill_server_thread 线程 error=TRUE; break; }AI 代码解读
kill_server() 先调用 close_connections()，再调用 unireg_end()
static void __cdecl kill_server(int sig_ptr) { ...... close_connections(); if (sig != MYSQL_KILL_SIGNAL && sig != 0) unireg_abort(1); /* purecov: inspected */ else unireg_end();AI 代码解读
结束线程的主要逻辑在 mysqld.cc:close_connections() 中
static void close_connections(void) ...... /* 下面这段代码结束监听端口 */ /* Abort listening to new connections */ DBUG_PRINT("quit",("Closing sockets")); if (!opt_disable_networking ) { if (mysql_socket_getfd(base_ip_sock) != INVALID_SOCKET) { (void) mysql_socket_shutdown(base_ip_sock, SHUT_RDWR); (void) mysql_socket_close(base_ip_sock); base_ip_sock= MYSQL_INVALID_SOCKET; } if (mysql_socket_getfd(extra_ip_sock) != INVALID_SOCKET) { (void) mysql_socket_shutdown(extra_ip_sock, SHUT_RDWR); (void) mysql_socket_close(extra_ip_sock); extra_ip_sock= MYSQL_INVALID_SOCKET; } } ...... /* 第一遍遍历线程列表 */ sql_print_information("Giving %d client threads a chance to die gracefully", static_cast<int>(get_thread_count())); mysql_mutex_lock(&LOCK_thread_count); Thread_iterator it= global_thread_list->begin(); for (; it != global_thread_list->end(); ++it) { THD *tmp= *it; DBUG_PRINT("quit",("Informing thread %ld that it's time to die", tmp->thread_id)); /* We skip slave threads & scheduler on this first loop through. */ /* 跳过 slave 相关线程，到 end_server() 函数内处理 */ if (tmp->slave_thread) continue; if (tmp->get_command() == COM_BINLOG_DUMP || tmp->get_command() == COM_BINLOG_DUMP_GTID) { ++dump_thread_count; continue; } /* 先标记为 KILL 给连接一个自我了断的机会 */ tmp->killed= THD::KILL_CONNECTION; ...... } mysql_mutex_unlock(&LOCK_thread_count); Events::deinit(); sql_print_information("Shutting down slave threads"); /* 此处断开 slave 相关线程 */ end_slave(); /* 第二遍遍历线程列表 */ if (dump_thread_count) { /* Replication dump thread should be terminated after the clients are terminated. Wait for few more seconds for other sessions to end. */ while (get_thread_count() > dump_thread_count && dump_thread_kill_retries) { sleep(1); dump_thread_kill_retries--; } mysql_mutex_lock(&LOCK_thread_count); for (it= global_thread_list->begin(); it != global_thread_list->end(); ++it) { THD *tmp= *it; DBUG_PRINT("quit",("Informing dump thread %ld that it's time to die", tmp->thread_id)); if (tmp->get_command() == COM_BINLOG_DUMP || tmp->get_command() == COM_BINLOG_DUMP_GTID) { /* 关闭DUMP线程 */ tmp->killed= THD::KILL_CONNECTION; ...... } } mysql_mutex_unlock(&LOCK_thread_count); } ...... /* 第三遍遍历线程列表 */ for (it= global_thread_list->begin(); it != global_thread_list->end(); ++it) { THD *tmp= *it; if (tmp->vio_ok()) { if (log_warnings) sql_print_warning(ER_DEFAULT(ER_FORCING_CLOSE),my_progname, tmp->thread_id, (tmp->main_security_ctx.user ? tmp->main_security_ctx.user : "")); /* 关闭连接，不等待语句结束，但是要回滚未提交线程 */ close_connection(tmp); } }AI 代码解读
close_connection() 中调用 THD::disconnect() 断开连接 连接断开后开始回滚事务
bool do_command(THD *thd) { ...... packet_length= my_net_read(net); // thd->disconnect() 后此处直接返回 ...... } void do_handle_one_connection(THD *thd_arg) { ...... while (thd_is_connection_alive(thd)) { if (do_command(thd)) //do_command 返回 error，跳出循环 break; } end_connection(thd); end_thread: close_connection(thd); /* 此处调用one_thread_per_connection_end() */ if (MYSQL_CALLBACK_ELSE(thd->scheduler, end_thread, (thd, 1), 0)) return; // Probably no-threads ...... }AI 代码解读
事务回滚调用链
trans_rollback(THD*) () THD::cleanup() () THD::release_resources() () one_thread_per_connection_end(THD*, bool) () do_handle_one_connection(THD*) () handle_one_connection ()AI 代码解读
unireg_end 调用 clean_up()
void clean_up(bool print_message) { /* 这里是一些释放内存和锁的操作 */ ...... /* 这里调用 innobase_shutdown_for_mysql purge all (innodb_fast_shutdown = 0) merge change buffer (innodb_fast_shutdown = 0） flush dirty page (innodb_fast_shutdown = 0,1) flush log buffer 都在这里面做 */ plugin_shutdown(); /* 这里是一些释放内存和锁的操作 */ ...... /* 删除 pid 文件，删除后 mysqld_safe不会重启 mysqld， 不然会认为 mysqld crash，尝试重启 */ delete_pid_file(MYF(0)); /* 这里是一些释放内存和锁的操作 */ ......AI 代码解读
innodb shutdown 分析
innodb shutdown 的主要操作在 logs_empty_and_mark_files_at_shutdown() 中
- 等待后台线程结束 srv_error_monitor_thread
- srv_lock_timeout_thread
- srv_monitor_thread
- buf_dump_thread
- dict_stats_thread
- 等待所有事物结束 trx_sys_any_active_transactions
- 等待后台线程结束
- worker threads: srv_worker_thread
- master thread: srv_master_thread
- purge thread: srv_purge_coordinator_thread
- 等待 buf_flush_lru_manager_thread 结束
- 等待 buf_flush_page_cleaner_thread 结束
- 等待 Pending checkpoint_writes, Pending log flush writes 结束
- 等待 buffer pool pending io 结束
- if (innodb_fast_shutdown == 2)
- flush log buffer 后 return
- log_make_checkpoint_at
- flush buffer pool
- write checkpoint
- 将 lsn 落盘 fil_write_flushed_lsn_to_data_files()
- 关闭所有文件
logs_empty_and_mark_files_at_shutdown() 结束后，innobase_shutdown_for_mysql() 再做一些资源清理工作即结束 shutdown 过程
