大事务检测能力

事务产生的Binlog大小超过rds_warn_max_binlog_cache_size时，为了提醒客户及时提交事务，系统会报WARNING到客户端。为了避免给客户端发送多个WARNING，限制事务中每个statement发送一次这个WARNING给客户端。

当配置rds_warn_max_binlog_cache_size为40KB(40960)：

CREATE TABLE t1 (
    -> a longtext
    -> ) DEFAULT CHARSET=latin1;
Query OK, 0 rows affected (0.12 sec)

mysql> show variables like 'rds_warn_max_binlog_cache_size';
+--------------------------------+-------+
| Variable_name                  | Value |
+--------------------------------+-------+
| rds_warn_max_binlog_cache_size | 40960 |
+--------------------------------+-------+
1 row in set (0.01 sec)

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO t1 VALUES (REPEAT('a',20000));
Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO t1 VALUES (REPEAT('a',20000));
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO t1 VALUES (REPEAT('a',20000));
Query OK, 1 row affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                             |
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 4008 | Recommend you to INSERT/UPDATE/DELETE rows in batches by multiple transactions. The current transaction required more than 'rds_warn_max_binlog_cache_size' (40960) bytes of storage. Which shall cause replication latency. Please commit it. |
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|        3 |
+----------+
1 row in set (0.01 sec)

mysql> commit;
Query OK, 0 rows affected (0.01 sec)

mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|        3 |
+----------+
1 row in set (0.01 sec)

mysql> INSERT INTO t1 VALUES (REPEAT('a',50000));
Query OK, 1 row affected, 1 warning (0.01 sec)

mysql> show warnings;
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message           |
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Warning | 4008 | Recommend you to INSERT/UPDATE/DELETE rows in batches by multiple transactions. The current transaction required more than 'rds_warn_max_binlog_cache_size' (40960) bytes of storage. Which shall cause replication latency. |
+---------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

• 查看当前连接的事务Binlog cache大小。

  mysql> CREATE TABLE t1 (
  ->   a longtext
  -> ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
  Query OK, 0 rows affected (0.10 sec)
  
  mysql> SHOW STATUS LIKE 'Rds_binlog_trx_cache_size';
  +---------------------------+-------+
  | Variable_name             | Value |
  +---------------------------+-------+
  | Rds_binlog_trx_cache_size | 0     |
  +---------------------------+-------+
  1 row in set (0.04 sec)
  
  mysql> begin;
  Query OK, 0 rows affected (0.00 sec)
  
  mysql> INSERT INTO t1 VALUES (REPEAT('a',20000));
  Query OK, 1 row affected (0.01 sec)
  
  mysql> SHOW STATUS LIKE 'Rds_binlog_trx_cache_size';
  +---------------------------+-------+
  | Variable_name             | Value |
  +---------------------------+-------+
  | Rds_binlog_trx_cache_size | 20150 |
  +---------------------------+-------+
  1 row in set (0.05 sec)
  mysql> commit;
  Query OK, 0 rows affected (0.00 sec)
  
  mysql> SHOW STATUS LIKE 'Rds_binlog_trx_cache_size';
  +---------------------------+-------+
  | Variable_name             | Value |
  +---------------------------+-------+
  | Rds_binlog_trx_cache_size | 0     |
  +---------------------------+-------+
  1 row in set (0.09 sec)

• 查看当前所有连接的事务Binlog cache大小。

  mysql> SHOW GLOBAL STATUS LIKE 'rds_binlog_trx_cache_size';
  +---------------------------+-------+
  | Variable_name             | Value |
  +---------------------------+-------+
  | Rds_binlog_trx_cache_size | 40300 |
  +---------------------------+-------+
  1 row in set (0.05 sec)