MySQL 8.0 DB启动相关源码介绍

主函数会调用mysqld.cc中的mysqld_main函数，进行DB的一系列初始化动作。

执行基本的线程库和堆内存初始化

#ifdef _WIN32
int win_main(int argc, char **argv)
#else
int mysqld_main(int argc, char **argv)
#endif
{
..
  /*
    Perform basic thread library and malloc initialization,
    to be able to read defaults files and parse options.
  */
  my_progname = argv[0];
  calculate_mysql_home_from_my_progname();

#ifndef _WIN32
#ifdef WITH_PERFSCHEMA_STORAGE_ENGINE
  pre_initialize_performance_schema();
#endif /*WITH_PERFSCHEMA_STORAGE_ENGINE */
  // For windows, my_init() is called from the win specific mysqld_main
  if (my_init())  // init my_sys library & pthreads
  {
    LogErr(ERROR_LEVEL, ER_MYINIT_FAILED);
    flush_error_log_messages();
    return 1;
  }
#endif /* _WIN32 */

加载参数文件

  orig_argc = argc;
  orig_argv = argv;
  my_getopt_use_args_separator = true;
  my_defaults_read_login_file = false;
  if (load_defaults(MYSQL_CONFIG_NAME, load_default_groups, &argc, &argv,
                    &argv_alloc)) {
    flush_error_log_messages();
    return 1;
  }

  argc_cached = argc;
  argv_cached = new (&argv_alloc) char *[argc_cached + 1];
  memcpy(argv_cached, argv, argc_cached * sizeof(char *));
  argv_cached[argc_cached] = nullptr;

设置数据目录

  /* Set data dir directory paths */
  strmake(mysql_real_data_home, get_relative_path(MYSQL_DATADIR),
          sizeof(mysql_real_data_home) - 1);

初始化参数的缓存

  /*
   Initialize variables cache for persisted variables, load persisted
   config file and append parse early  read only persisted variables
   to command line options if present.
  */
  bool arg_separator_added = false;
  if (persisted_variables_cache.init(&argc, &argv) ||
      persisted_variables_cache.load_persist_file() ||
      persisted_variables_cache.append_parse_early_variables(
          &argc, &argv, arg_separator_added)) {
    flush_error_log_messages();
    return 1;
  }

  remaining_argc = argc;
  remaining_argv = argv;

  init_variable_default_paths();

如果开启了performance_schema，初始化相关配置

#ifdef WITH_PERFSCHEMA_STORAGE_ENGINE
  /*
    Initialize the array of performance schema instrument configurations.
  */
  init_pfs_instrument_array();
#endif /* WITH_PERFSCHEMA_STORAGE_ENGINE */

初始化资源组

  // Initialize the resource group subsystem.
  auto res_grp_mgr = resourcegroups::Resource_group_mgr::instance();
  if (!is_help_or_validate_option() && !opt_initialize) {
    if (res_grp_mgr->init()) {
      LogErr(ERROR_LEVEL, ER_RESOURCE_GROUP_SUBSYSTEM_INIT_FAILED);
      unireg_abort(MYSQLD_ABORT_EXIT);
    }
  }

审计接口初始化

   /* Initialize audit interface globals. Audit plugins are inited later. */
  mysql_audit_initialize(); 

查询日志初始化

  /*
    Perform basic query log initialization. Should be called after
    MY_INIT, as it initializes mutexes.
  */
  query_logger.init();

信号初始化

  my_init_signals();

决定默认的数据库端口和socket名字

  /* Determine default TCP port and unix socket name */
  set_ports();

初始化网络

 if (network_init()) unireg_abort(MYSQLD_ABORT_EXIT);

初始化GTID的设置

  if (opt_bin_log) {
    /*
      Initialize GLOBAL.GTID_EXECUTED and GLOBAL.GTID_PURGED from
      gtid_executed table and binlog files during server startup.
    */
    Gtid_set *executed_gtids =
        const_cast<Gtid_set *>(gtid_state->get_executed_gtids());
    Gtid_set *lost_gtids = const_cast<Gtid_set *>(gtid_state->get_lost_gtids());
    Gtid_set *gtids_only_in_table =
        const_cast<Gtid_set *>(gtid_state->get_gtids_only_in_table());
    Gtid_set *previous_gtids_logged =
        const_cast<Gtid_set *>(gtid_state->get_previous_gtids_logged());

    Gtid_set purged_gtids_from_binlog(global_sid_map, global_sid_lock);
    Gtid_set gtids_in_binlog(global_sid_map, global_sid_lock);
    Gtid_set gtids_in_binlog_not_in_table(global_sid_map, global_sid_lock);

    if (mysql_bin_log.init_gtid_sets(
            &gtids_in_binlog, &purged_gtids_from_binlog,
            opt_source_verify_checksum, true /*true=need lock*/,
            nullptr /*trx_parser*/, nullptr /*partial_trx*/,
            true /*is_server_starting*/))
      unireg_abort(MYSQLD_ABORT_EXIT);

将pid保存到文件中

  /* Save pid of this process in a file */
  if (!opt_initialize) {
    if (create_pid_file()) abort = true;
  }

读取优化器成本模型配置表

  /* Read the optimizer cost model configuration tables */
  if (!opt_initialize) reload_optimizer_cost_constants();

  if (
      /*
        Read components table to restore previously installed components. This
        requires read access to mysql.component table.
      */
      (!opt_initialize && mysql_component_infrastructure_init()) ||
      mysql_rm_tmp_tables()) {
    abort = true;
  }

检查binlog

  check_binlog_cache_size(nullptr);
  check_binlog_stmt_cache_size(nullptr);

  binlog_unsafe_map_init();

  ReplicaInitializer replica_initializer(opt_initialize, opt_skip_replica_start,
                                         rpl_channel_filters,
                                         &opt_replica_skip_errors);

初始化存储引擎等核心模块

  server_components_initialized();

输出运行的pid号

  if (opt_daemonize) {
    if (nstdout != nullptr) {
      // Show the pid on stdout if daemonizing and connected to tty
      fprintf(nstdout, "mysqld is running as pid %lu\n", current_pid);
      fclose(nstdout);
      nstdout = nullptr;

接收连接

  mysqld_socket_acceptor->connection_event_loop();