基于MySQL内核的SQL限流设计与实现

// 更新
static bool update_delimiter(sys_var *self, THD *thd, enum_var_type type)
{
  reload_rules(thd);
}


// 校验
static bool check_delimiter(sys_var *self, THD *thd, set_var *var)
{
  judge(var->value);
  judge(str);
  judge(length);
}

int mysqld_main(int argc, char **argv)
{
  ...
  load_rules();
  ...
}

void dec_conc(THD *thd, int command)
{
  // 根据查询类型在对应链表找节点
  node = find_by_id(list, thd->id);


  // 并发数量减1
  if (node) {
    __sync_sub_and_fetch(&(node->concur), 1);
  }
  
  // 重置状态
  thd->id = 0;
}

void clean_up()
{
  cleanup();
}

/* The flow control does not take effect on system tables */
  if (check_system_table(first_table->db)) {
    return ret;
  }

bool check_rule_matched(THD* thd, LIST* list)
{
  while (满足条件，无异常) {
    // 根据大小写开关是否打开，分别进行模式串匹配
    it = find(query_str, item->key_array[nums]);
      
    // 如果it为空，没有匹配到，查看下一个list，否则继续匹配当前限流规则节点
    judge();
  }


  // 匹配成功，或者对下一个节点进行匹配
}

class Du_table_access {
public:
  Du_table_access() : m_drop_thd_object(NULL) {}
  virtual ~Du_table_access() {}


  // 初始化打开表的环境、锁表并且打开表
  bool init(THD **thd, TABLE **table, bool is_write);
  
  // 关闭表，清理环境
  bool deinit(THD *thd, TABLE *table, bool error, bool need_commit);
  
  // 设置打开表的策略
  void before_open(THD *thd);
  
  // 如果需要的话创建线程，大部分时候并不需要，因为手动执行读取数据的时候已经在线程中了
  THD *create_thd();
  
  // 如果手动创建了 thd，则需要手动清理
  void drop_thd(THD *thd);
};

SET @cmd= "CREATE TABLE IF NOT EXISTS du_flow_control_rules (
    id BIGINT NOT NULL AUTO_INCREMENT COMMENT 'Id of the flow control rules.',
    type ENUM('SELECT', 'UPDATE', 'INSERT', 'DELETE') CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL COMMENT 'Type of flow control rules.',
    max_concur INT NOT NULL COMMENT 'Max concurrent of sql.',
    orig_str VARCHAR(1024) CHARSET SET utf8mb4 COLLATE utf8mb4_bin NOT NULL COMMENT 'Original string of flow control rules.',
    PRIMARY KEY(id)) DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin COMMENT 'Flow control rules info.'";


SET @str=IF(@have_innodb <> 0, CONCAT(@cmd, ' ENGINE= INNODB;'), CONCAT(@cmd, ' ENGINE= MYISAM;'));
PREPARE stmt FROM @str;
EXECUTE stmt;
DROP PREPARE stmt;

DELIMITER $$


CREATE DEFINER='root'@'localhost' PROCEDURE mysql.add_flow_control ( IN sql_type INT, IN str VARCHAR(1024), IN max_num INT )
    COMMENT '
Description
-----------
Basic functions for inserting rules.
It is not recommended to call it directly, but to call it through add_select_flow_control、
add_update_flow_control、add_update_flow_control and add_delete_flow_control.
'
    SQL SECURITY INVOKER
BEGIN
    IF (sql_type = 0) THEN
        INSERT INTO mysql.du_flow_control_rules(type, max_concur, orig_str) VALUES('SELECT', max_num, str);
    ELSEIF (sql_type = 1) THEN
        INSERT INTO mysql.du_flow_control_rules(type, max_concur, orig_str) VALUES('UPDATE', max_num, str);
    ELSEIF (sql_type = 2) THEN
        INSERT INTO mysql.du_flow_control_rules(type, max_concur, orig_str) VALUES('INSERT', max_num, str);
    ELSEIF (sql_type = 3) THEN 
        INSERT INTO mysql.du_flow_control_rules(type, max_concur, orig_str) VALUES('DELETE', max_num, str);
    ELSE
        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'Sql type is error, please input correctly.';
    END IF;
END$$


CREATE DEFINER='root'@'localhost' PROCEDURE mysql.add_select_flow_control (IN str VARCHAR(1024), IN max_num INT )
    COMMENT '
Description
-----------
Used to add select type rules to the current rule table.


Parameters
-----------


str (VARCHAR(1024)):
  The string of select rules entered by user.


max_num (INT):
  The number of queries that can be executed concurrently.


Example
--------


mysql> SELECT * FROM du_flow_control_rules;
Empty set (0.00 sec)


mysql> CALL add_select_flow_control(''select~from~t1'', 100);
Query OK, 1 row affected (0.00 sec)


mysql> SELECT * FROM du_flow_control_rules;
+----+--------+------------+----------------+
| id | type   | max_concur | orig_str       |
+----+--------+------------+----------------+
|  1 | SELECT |        100 | select~from~t1 |
+----+--------+------------+----------------+
1 row in set (0.00 sec)
'
    SQL SECURITY INVOKER
BEGIN
    CALL add_flow_control(0, str, max_num);
END$$
DELIMITER ;