mysql的半同步复制-semisync是基于默认的异步复制和完全同步复制之间,它是在master在执行完客户端提交的事务后不是立刻返回给客户端,而是等待至少一个slave收到并写到relay log中才返回给客户端。相对于异步复制,semisync提高了数据的安全性,但是又比完全同步性能好,所以master和slave之间的时间一定要一致,以免造成semisync失败。mysql的半同步复制的插件是由Google免费提供的在mysql的$basedir/lib/plugin下有相应的动态库文件,linux中是.so,DOS系统中是.dll,在默认情况下mysql是没有装载semisync的插件,所以要制作semisync要手动在mysql的shell中装载插件,下面就简单的说一说mysql的semisync配置,这里要注意要使用mysql的super用户来配置,并且mysql要5.5及以上版本才有,并且要在有异步复制的基础上才可以做配置
#master中 mysql> install plugin rpl_semi_sync_master soname ‘semisync_master.so‘; Query OK, 0 rows affected (0.00 sec) mysql> show global variables like ‘%semi%‘; +------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rpl_semi_sync_master_enabled | OFF | | rpl_semi_sync_master_timeout | 10000 | | rpl_semi_sync_master_trace_level | 32 | | rpl_semi_sync_master_wait_no_slave | ON | +------------------------------------+-------+ 4 rows in set (0.01 sec) mysql> set global rpl_semi_sync_master_enabled = 1;#开启master上的semisync,设置超时时间,可以通过设置rpl_semi_sync_master_timeout变量来修改,默认单位为毫秒 Query OK, 0 rows affected (0.00 sec) mysql> show status like ‘%Rpl_semi_sync%‘; +--------------------------------------------+-------+ | Variable_name | Value | +--------------------------------------------+-------+ | Rpl_semi_sync_master_clients | 1 | | Rpl_semi_sync_master_net_avg_wait_time | 565 | | Rpl_semi_sync_master_net_wait_time | 3391 | | Rpl_semi_sync_master_net_waits | 6 | | Rpl_semi_sync_master_no_times | 1 | | Rpl_semi_sync_master_no_tx | 12 | | Rpl_semi_sync_master_status | ON | | Rpl_semi_sync_master_timefunc_failures | 0 | | Rpl_semi_sync_master_tx_avg_wait_time | 588 | | Rpl_semi_sync_master_tx_wait_time | 3528 | | Rpl_semi_sync_master_tx_waits | 6 | | Rpl_semi_sync_master_wait_pos_backtraverse | 0 | | Rpl_semi_sync_master_wait_sessions | 0 | | Rpl_semi_sync_master_yes_tx | 6 | +--------------------------------------------+-------+ 14 rows in set (0.00 sec) #slave中 mysql> install plugin rpl_semi_sync_slave soname ‘semisync_slave.so‘; Query OK, 0 rows affected (0.00 sec) mysql> show global variables like ‘%semi%‘; +---------------------------------+-------+ | Variable_name | Value | +---------------------------------+-------+ | rpl_semi_sync_slave_enabled | OFF | | rpl_semi_sync_slave_trace_level | 32 | +---------------------------------+-------+ 2 rows in set (0.00 sec) mysql> set global rpl_semi_sync_slave_enabled = 1; Query OK, 0 rows affected (0.00 sec) mysql> stop slave IO_THREAD;start slave IO_THREAD;#重启slave上的IO线程 Query OK, 0 rows affected (0.09 sec) Query OK, 0 rows affected (0.00 sec) mysql> show status like ‘%Rpl_semi_sync%‘; +----------------------------+-------+ | Variable_name | Value | +----------------------------+-------+ | Rpl_semi_sync_slave_status | ON | +----------------------------+-------+ 1 row in set (0.00 sec)
这样简单的semisync就配置好了,这里要注意的是如果master超过超时时间没有接收到slave的消息时会自动转为异步复制,当然如果不需要semisync可以直接uninstall相应的插件
mysql> uninstall plugin rpl_semi_sync_master; Query OK, 0 rows affected (0.00 sec) mysql> uninstall plugin rpl_semi_sync_slave; Query OK, 0 rows affected (0.00 sec)
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原文地址:http://jim123.blog.51cto.com/4763600/1903678