我正在尝试在5.7上设置mysql mts复制。
我正在使用LOGICAL_CLOCK复制一个数据库：
mysql> show variables like 'slave_parallel%';
+------------------------+---------------+
| Variable_name | Value |
+------------------------+---------------+
| slave_parallel_type | LOGICAL_CLOCK |
| slave_parallel_workers | 4 |
+------------------------+---------------+
2 rows in set (0.00 sec)
但只有一个线程处于活动状态，其他线程只是等待：
mysql> show processlist;
+--------+-------------+-----------------------+--------------------+---------+--------+---------------------------------------------+----------------------------------------------------------------------------+-----------+---------------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined |
+--------+-------------+-----------------------+--------------------+---------+--------+---------------------------------------------+----------------------------------------------------------------------------+-----------+---------------+
| 8103 | system user | | NULL | Connect | 72189 | Waiting for master to send event | NULL | 0 | 0 |
| 8104 | system user | | NULL | Connect | 0 | Waiting for dependent transaction to commit | NULL | 0 | 0 |
| 8105 | system user | | db_repl | Connect | 344764 | System lock | DELETE FROM docs WHERE id = 21099810 | 0 | 0 |
| 8106 | system user | | NULL | Connect | 344765 | Waiting for an event from Coordinator | NULL | 0 | 0 |
| 8107 | system user | | NULL | Connect | 344771 | Waiting for an event from Coordinator | NULL | 0 | 0 |
| 8108 | system user | | NULL | Connect | 344813 | Waiting for an event from Coordinator | NULL | 0 | 0 |
| 600637 | sphinx | localhost | mysql | Query | 0 | starting | show processlist | 0 | 0 |
+--------+-------------+-----------------------+--------------------+---------+--------+---------------------------------------------+----------------------------------------------------------------------------+-----------+---------------+
7 rows in set (0.00 sec)
如何调试配置以查看线程未激活的原因？
P.S。我有高负载主机并且有很大的从机延迟，因为slave只有一个线程可以复制，所以我需要增加从机线程以减少“Seconds_behind_master”。