默认情况下process如下

mysql> show processlist;
+----+-------------+-----------+--------+---------+-------+--------------------------------------------------------+------------------+
| Id | User        | Host      | db     | Command | Time  | State                                                  | Info             |
+----+-------------+-----------+--------+---------+-------+--------------------------------------------------------+------------------+
|  8 | system user |           | NULL   | Connect | 70100 | Waiting for master to send event                       | NULL             |//IO线程
|  9 | system user |           | NULL   | Connect | 57345 | Slave has read all relay log; waiting for more updates | NULL             |//中继线程，单线程
| 10 | root        | localhost | master | Query   |     0 | starting                                               | show processlist |
+----+-------------+-----------+--------+---------+-------+--------------------------------------------------------+------------------+
3 rows in set (0.00 sec)

开启并行复制,编辑slave的/etc/my.cnf,新增如下信息

slave-parallel-type=LOGICAL_CLOCK//设置通过组提交，database是几个数据库就起几个线程，当只有一个数据库时，一个线程不够，所以引入组复制，一组一个线程
slave-parallel-workers=16 //并行复制sql线程数
master_info_repository=TABLE //data/mysql里的master.info和relay-log.info以表的形式存到数据库中
relay_log_info_repository=TABLE
relay_log_recovery=ON//激活中继日志

重启mysql后再次进入mysql查看

mysql> show processlist;
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
| Id | User        | Host      | db   | Command | Time | State                                                  | Info             |
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
|  1 | system user |           | NULL | Connect |   36 | Waiting for master to send event                       | NULL             |
|  2 | system user |           | NULL | Connect |   35 | Slave has read all relay log; waiting for more updates | NULL             |
|  3 | system user |           | NULL | Connect |   36 | Waiting for an event from Coordinator                  | NULL             |
|  4 | system user |           | NULL | Connect |   36 | Waiting for an event from Coordinator                  | NULL             |
|  5 | system user |           | NULL | Connect |   36 | Waiting for an event from Coordinator                  | NULL             |
|  6 | system user |           | NULL | Connect |   36 | Waiting for an event from Coordinator                  | NULL             |
|  8 | root        | localhost | NULL | Query   |    0 | starting                                               | show processlist |
+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+
7 rows in set (0.00 sec)

可以看到，多了四条数据，这四条数据代表4个sql线程为协程线程，等待转发