• 并行复制

  • 社区版5.6中新增
  • 并行是指从库多线程apply binlog
  • 库级别并行应用binlog，同一个库数据更改还是串行的（5.7版并行复制基于事务组）

  设置

set global slave_parallel_workers=10;设置sql线程数为10

步骤：

#从库
mysql> show variables like '%slave_par%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| slave_parallel_workers | 0     |#关闭状态
+------------------------+-------+
1 row in set (0.00 sec)

mysql> set global slave_parallel_workers=10;
Query OK, 0 rows affected (0.00 sec)

#查看线程，SQL线程数量并没有改变，因为没有重新启动slave
mysql> show processlist\G
*************************** 1. row ***************************
     Id: 15
   User: system user
   Host: 
     db: NULL
Command: Connect
   Time: 59458
  State: Waiting for master to send event
   Info: NULL
*************************** 2. row ***************************
     Id: 16
   User: system user
   Host: 
     db: NULL
Command: Connect
   Time: 59550
  State: Slave has read all relay log; waiting for the slave I/O thread to update it
   Info: NULL
*************************** 3. row ***************************
     Id: 17
   User: root
   Host: localhost
     db: NULL
Command: Query
   Time: 0
  State: init
   Info: show processlist
3 rows in set (0.00 sec)

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

mysql> start slave;
Query OK, 0 rows affected, 1 warning (0.02 sec)

mysql> show processlist;
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
| Id | User        | Host      | db   | Command | Time | State                                                                       | Info             |
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
| 17 | root        | localhost | NULL | Query   |    0 | init                                                                        | show processlist |
| 18 | system user |           | NULL | Connect |    8 | Waiting for master to send event                                            | NULL             |
| 19 | system user |           | NULL | Connect |    8 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL             |
| 20 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 21 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 22 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 23 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 24 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 25 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 26 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 27 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 28 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
| 29 | system user |           | NULL | Connect |    8 | Waiting for an event from Coordinator                                       | NULL             |
+----+-------------+-----------+------+---------+------+-----------------------------------------------------------------------------+------------------+
13 rows in set (0.00 sec)