本文环境
主库：CentOS6.5 x64 192.168.0.65 mysql-5.6.29 备库：CentOS6.5 x64 192.168.0.66 mysql-5.6.29接上文: mysql-5.6主从同步配置示例
半同步复制的概念:
mysql5.5.x以上版本支持半同步复制，当Slave主机连接到Master时，能够查看其是否处于半同步复制的机制。当Master上开启半同步复制的功能时，至少应该有一个Slave开启其功能。此时，一个线程在Master上提交事务将受到阻塞，直到得知一个已开启半同步复制功能的Slave已收到此事务的所有事件，或等待超时。当一个事务的事件都已写入其relay-log中且已刷新到磁盘上，Slave才会告知已收到。如果等待超时，也就是Master没被告知已收到，此时Master会自动转换为异步复制的机制。当至少一个半同步的Slave赶上了，Master与其Slave自动转换为半同步复制的机制。半同步复制的功能要在Master，Slave都开启，半同步复制才会起作用；否则，只开启一边，它依然为异步复制。一、半同步主服务器配置
1. mysql主服务器配置
(1) 在主服务器上加入半自动配置文件参数
# vi /etc/my.cnf
[mysqld]
log-bin = master-bin log-bin-index = master-bin.index binlog_format = mixed server-id = 1 expire-logs-days = 7 rpl_semi_sync_master_enabled = 1 rpl_semi_sync_master_timeout = 1000 # 1 second(2) 安装半同步配置插件
mysql> install plugin rpl_semi_sync_master soname 'semisync_master.so';
(3) 配置半同步插件
mysql> show global variables like '%rpl%';
+------------------------------------+-------+ | Variable_name | Value | +------------------------------------+-------+ | rpl_recovery_rank | 0 | | 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) 启用半同步插件
mysql> set global rpl_semi_sync_master_enabled =1;
(5) 配置超时
mysql> set rpl_semi_sync_master_timeout 1000;
mysql> show global status like 'rpl_semi%';
+--------------------------------------------+-------+ | Variable_name | Value | +--------------------------------------------+-------+ | Rpl_semi_sync_master_clients | 0 | | Rpl_semi_sync_master_net_avg_wait_time | 0 | | Rpl_semi_sync_master_net_wait_time | 0 | | Rpl_semi_sync_master_net_waits | 0 | | Rpl_semi_sync_master_no_times | 0 | | Rpl_semi_sync_master_no_tx | 0 | | Rpl_semi_sync_master_status | ON | | Rpl_semi_sync_master_timefunc_failures | 0 | | Rpl_semi_sync_master_tx_avg_wait_time | 0 | | Rpl_semi_sync_master_tx_wait_time | 0 | | Rpl_semi_sync_master_tx_waits | 0 | | Rpl_semi_sync_master_wait_pos_backtraverse | 0 | | Rpl_semi_sync_master_wait_sessions | 0 | | Rpl_semi_sync_master_yes_tx | 0 | +--------------------------------------------+-------+ 14 rows in set (0.00 sec)其它一些性能及相关参数：
2. 重启主服务器,使配置文件生效
# service mysqld restart
二、半同步从服务器配置
1. mysql从服务器配置
(1) 加入如下半同步配置。
# vi /etc/my.cnf
[mysqld]
log-bin = mysql-bin binlog_format = mixed server-id = 11 relay-log = slave-relay-bin relay-log-index = slave-relay-bin.index replicate_wild_ignore_table = mysql.% rpl_semi_sync_slave_enabled = 1(2) 安装半同步配置插件
mysql> install plugin rpl_semi_sync_slave soname 'semisync_slave.so';
Query OK, 0 rows affected (0.00 sec)(3) 配置半同步插件
mysql> show global variables like '%rpl%';
+---------------------------------+----------+ | Variable_name | Value | +---------------------------------+----------+ | rpl_semi_sync_slave_enabled | ON | | rpl_semi_sync_slave_trace_level | 32 | | rpl_stop_slave_timeout | 31536000 | +---------------------------------+----------+ 3 rows in set (0.00 sec)(4) 启用半同步插件
mysql> set global rpl_semi_sync_master_enabled =1;
Query OK, 0 rows affected (0.00 sec)mysql> show global variables like '%rpl%';
+---------------------------------+----------+ | Variable_name | Value | +---------------------------------+----------+ | rpl_semi_sync_slave_enabled | ON | | rpl_semi_sync_slave_trace_level | 32 | | rpl_stop_slave_timeout | 31536000 | +---------------------------------+----------+ 3 rows in set (0.00 sec)(5) 重启同步进程
mysql> stop slave;
Query OK, 0 rows affected (0.02 sec)mysql> start slave;
Query OK, 0 rows affected (0.02 sec)mysql> show slave status \G;
*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.0.65 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000005 Read_Master_Log_Pos: 120 Relay_Log_File: testdb-relay-bin.000012 Relay_Log_Pos: 284 Relay_Master_Log_File: master-bin.000005 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: mysql.% Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 120 Relay_Log_Space: 622 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 1 Master_UUID: c8bb22a1-024e-11e6-a1e8-000c29225fa0 Master_Info_File: /usr/local/mysql-5.6.29-linux-glibc2.5-x86_64/data/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Slave has read all relay log; waiting for the slave I/O thread to update it Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: Auto_Position: 0 1 row in set (0.00 sec)2. 在主服务器上可以查看有1个从服务器连接过来
mysql> show global status like 'rpl_semi%';
+--------------------------------------------+-------+ | Variable_name | Value | +--------------------------------------------+-------+ | Rpl_semi_sync_master_clients | 1 | | Rpl_semi_sync_master_net_avg_wait_time | 0 | | Rpl_semi_sync_master_net_wait_time | 0 | | Rpl_semi_sync_master_net_waits | 0 | | Rpl_semi_sync_master_no_times | 0 | | Rpl_semi_sync_master_no_tx | 0 | | Rpl_semi_sync_master_status | ON | | Rpl_semi_sync_master_timefunc_failures | 0 | | Rpl_semi_sync_master_tx_avg_wait_time | 0 | | Rpl_semi_sync_master_tx_wait_time | 0 | | Rpl_semi_sync_master_tx_waits | 0 | | Rpl_semi_sync_master_wait_pos_backtraverse | 0 | | Rpl_semi_sync_master_wait_sessions | 0 | | Rpl_semi_sync_master_yes_tx | 0 | +--------------------------------------------+-------+ 14 rows in set (0.00 sec)3. 重启从服务器,使配置文件生效
# service mysqld restart