Mysql 5.7从节点配置多线程主从复制的方法详解

前言

Mysql 采用多线程进行复制是从 Mysql 5.6 开始支持的内容，但是 5.6 版本下有缺陷，虽然支持多线程，但是每个数据库只能一个线程，也就是说如果我们只有一个数据库，则主从复制时也只有一个线程在工作。相当于还是以前的单线程。从 Mysql 5.7 开始支持同一数据库下并行主从复制。不过默认情况下，还是单数据库单个线程，如果需要使用多线程，需要在从节点进行配置。

Mysql 5.7 对主从复制增加了一种类型，共有两种类型，如下：

DATABASE 基于库的并行复制，每个数据库对应一个复制线程
LOGICAL_CLOCK 基于组提交的并行复制方式，同一个数据库下可以有多个线程

下面的步骤，在从节点上进行配置。

查看当前配置

在开始配置之前，我们先看一下当前配置下的主从复制的进程数。

mysql> show processlist;+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+| Id | User  | Host  | db | Command | Time | State             | Info    |+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+| 1 | system user |   | NULL | Connect | 91749 | Waiting for master to send event      | NULL    || 2 | system user |   | NULL | Connect | 208 | Slave has read all relay log; waiting for more updates | NULL    || 37 | root  | localhost | NULL | Query |  0 | starting            | show processlist |+----+-------------+-----------+------+---------+-------+--------------------------------------------------------+------------------+3 rows in set (0.00 sec)

下面查看复制类型和并行数量配置

mysql> show variables like 'slave_parallel_type';+---------------------+----------+| Variable_name  | Value |+---------------------+----------+| slave_parallel_type | DATABASE |+---------------------+----------+1 row in set (0.00 sec)

mysql> show variables like 'slave_parallel_workers';+------------------------+-------+| Variable_name   | Value |+------------------------+-------+| slave_parallel_workers | 0  |+------------------------+-------+1 row in set (0.01 sec)

配置多线程

1、停止从节点复制

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

mysql> set global slave_parallel_type='logical_clock';Query OK, 0 rows affected (0.00 sec)mysql> show variables like 'slave_parallel_type';+---------------------+---------------+| Variable_name  | Value   |+---------------------+---------------+| slave_parallel_type | LOGICAL_CLOCK |+---------------------+---------------+1 row in set (0.01 sec)

mysql> set global slave_parallel_workers=4;Query OK, 0 rows affected (0.00 sec)mysql> show variables like 'slave_parallel_workers';+------------------------+-------+| Variable_name   | Value |+------------------------+-------+| slave_parallel_workers | 4  |+------------------------+-------+1 row in set (0.00 sec)

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

mysql> show processlist;+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+| Id | User  | Host  | db | Command | Time | State             | Info    |+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+| 37 | root  | localhost | NULL | Query | 0 | starting            | show processlist || 38 | system user |   | NULL | Connect | 8 | Waiting for master to send event      | NULL    || 39 | system user |   | NULL | Connect | 7 | Slave has read all relay log; waiting for more updates | NULL    || 40 | system user |   | NULL | Connect | 8 | Waiting for an event from Coordinator     | NULL    || 41 | system user |   | NULL | Connect | 8 | Waiting for an event from Coordinator     | NULL    || 42 | system user |   | NULL | Connect | 8 | Waiting for an event from Coordinator     | NULL    || 43 | system user |   | NULL | Connect | 8 | Waiting for an event from Coordinator     | NULL    |+----+-------------+-----------+------+---------+------+--------------------------------------------------------+------------------+7 rows in set (0.00 sec)

总结

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