先看下slave_exec_mod官方描述
Controls whether IDEMPOTENT or STRICT mode is used in replication conflict resolution and error checking.IDEMPOTENT mode causes suppression of duplicate-key and no-key-found errors.
This mode is needed for multi-master replication, circular replication, and some other special replication scenarios for MySQL Cluster Replication.
[plain] view plaincopyprint
SLAVE@root@test 07:21:41>show variables like 'slave_exec_mode';
+-----------------+--------+
| Variable_name | Value |
+-----------------+--------+
| slave_exec_mode | STRICT |
+-----------------+--------+
1 row in set (0.00 sec)
SLAVE@root@test 07:21:42>
SLAVE@root@test 07:21:41>show variables like 'slave_exec_mode';
+-----------------+--------+
| Variable_name | Value |
+-----------------+--------+
| slave_exec_mode | STRICT |
+-----------------+--------+
1 row in set (0.00 sec)
SLAVE@root@test 07:21:42>
意思是说slave_exec_mod默认是STRICT可选值是IDEMPOTENT，在多主大型复制系统中建议使用IDEMPOTENT值，它避免duplicate-key 和 no-key-found等错误。这个参数是动态的，可以直接修改。
[plain] view plaincopyprint
SLAVE@root@test 07:39:58>show variables like 'slave_exec_mode';
+-----------------+------------+
| Variable_name | Value |
+-----------------+------------+
| slave_exec_mode | IDEMPOTENT |
+-----------------+------------+
1 row in set (0.00 sec)
SLAVE@root@test 07:40:09>set global slave_exec_mode='strict';
Query OK, 0 rows affected (0.00 sec)
SLAVE@root@test 07:40:23>show variables like 'slave_exec_mode';
+-----------------+--------+
| Variable_name | Value |
+-----------------+--------+
| slave_exec_mode | STRICT |
+-----------------+--------+
1 row in set (0.00 sec)
SLAVE@root@test 07:40:24>set global slave_exec_mode='IDEMPOTENT';
Query OK, 0 rows affected (0.00 sec)