注：若主MYSQL服务器已经存在，只是后期才搭建从MYSQL服务器，在置配数据同步前应先将主MYSQL服务器的要同步的数据库拷贝到从MYSQL服务器上（如先在主MYSQL上备份数据库，再用备份在从MYSQL服务器上恢复）
master mysql主机：
server-id = 1
log-bin=mysql-bin
binlog_format=mixed
log-bin-index=mysql-bin.index
rpl_semi_sync_master_enabled=1
rpl_semi_sync_master_timeout=10000
rpl_semi_sync_slave_enabled=1
relay_log_purge=0
relay-log= relay-bin
relay-log-index = relay-bin.index
注：
rpl_semi_sync_master_enabled=1 1表是启用，0表示关闭
rpl_semi_sync_master_timeout=10000：毫秒单位，该参数主服务器等待确认消息10秒后，不再等待，变为异步方式。
Candidate 主机：
server-id = 2
log-bin=mysql-bin
binlog_format=mixed
log-bin-index=mysql-bin.index
relay_log_purge=0
relay-log= relay-bin
relay-log-index = slave-relay-bin.index
rpl_semi_sync_master_enabled=1
rpl_semi_sync_master_timeout=10000
rpl_semi_sync_slave_enabled=1
注：relay_log_purge=0，禁止 SQL 线程在执行完一个 relay log 后自动将其删除，对于MHA场景下，对于某些滞后从库的恢复依赖于其他从库的relaylog，因此采取禁用自动删除功能
Slave主机：
Server-id = 3
log-bin = mysql-bin
relay-log = relay-bin
relay-log-index = slave-relay-bin.index
read_only = 1
rpl_semi_sync_slave_enabled = 1
查看半同步相关信息
mysql> show variables like '%rpl_semi_sync%';
查看半同步状态：
mysql> show status like '%rpl_semi_sync%';
| Rpl_semi_sync_master_clients | 2 |
重点关注的参数：
rpl_semi_sync_master_status ：显示主服务是异步复制模式还是半同步复制模式
rpl_semi_sync_master_clients ：显示有多少个从服务器配置为半同步复制模式
rpl_semi_sync_master_yes_tx ：显示从服务器确认成功提交的数量
rpl_semi_sync_master_no_tx ：显示从服务器确认不成功提交的数量
rpl_semi_sync_master_tx_avg_wait_time ：事务因开启 semi_sync ，平均需要额外等待的时间
rpl_semi_sync_master_net_avg_wait_time ：事务进入等待队列后，到网络平均等待时间
三、配置mysql-mha
所有mysql节点安装
rpm -ivh perl-DBD-MySQL-4.013-3.el6.i686.rpm [yum -y install perl-DBD-MySQL]
rpm -ivh mha4mysql-node-0.56-0.el6.noarch.rpm
2. manage需安装依赖的perl包
rpm -ivh perl-Config-Tiny-2.12-7.1.el6.noarch.rpm
rpm -ivh perl-DBD-MySQL-4.013-3.el6.i686.rpm [yum -y install perl-DBD-MySQL]
rpm -ivh compat-db43-4.3.29-15.el6.x86_64.rpm
rpm -ivh perl-Mail-Sender-0.8.16-3.el6.noarch.rpm
rpm -ivh perl-Parallel-ForkManager-0.7.9-1.el6.noarch.rpm
rpm -ivh perl-TimeDate-1.16-11.1.el6.noarch.rpm
rpm -ivh perl-MIME-Types-1.28-2.el6.noarch.rpm
rpm -ivh perl-MailTools-2.04-4.el6.noarch.rpm
rpm -ivh perl-Email-Date-Format-1.002-5.el6.noarch.rpm
rpm -ivh perl-Params-Validate-0.92-3.el6.x86_64.rpm
rpm -ivh perl-Params-Validate-0.92-3.el6.x86_64.rpm
rpm -ivh perl-MIME-Lite-3.027-2.el6.noarch.rpm
rpm -ivh perl-Mail-Sendmail-0.79-12.el6.noarch.rpm
rpm -ivh perl-Log-Dispatch-2.27-1.el6.noarch.rpm
yum install -y perl-Time-HiRes-1.9721-144.el6.x86_64
rpm -ivh mha4mysql-manager-0.56-0.el6.noarch.rpm
3. 配置mha
配置文件位于管理节点，通常包括每一个mysql server的主机名，mysql用户名，密码，工作目录等等。
mkdir /etc/masterha/
vim /etc/masterha/app1.cnf
[server default]
user=mhauser
password=123456
manager_workdir=/data/masterha/app1
manager_log=/data/masterha/app1/manager.log
remote_workdir=/data/masterha/app1
ssh_user=root
repl_user=repl
repl_password=123456
ping_interval=1
[server1]
hostname=192.168.137.134
port=3306
master_binlog_dir=/usr/local/mysql/data
candidate_master=1
[server2]
hostname=192.168.137.130
port=3306
master_binlog_dir=/usr/local/mysql/data
candidate_master=1
[server3]
hostname=192.168.137.146
port=3306
master_binlog_dir=/usr/local/mysql/data
no_master=1
配关配置项的解释：
manager_workdir=/masterha/app1//设置manager的工作目录
manager_log=/masterha/app1/manager.log//设置manager的日志
user=manager//设置监控用户manager
password=123456 //监控用户manager的密码
ssh_user=root //ssh连接用户
repl_user=mharep //主从复制用户
repl_password=123.abc//主从复制用户密码
ping_interval=1 //设置监控主库，发送ping包的时间间隔，默认是3秒，尝试三次没有回应的时候自动进行failover
master_binlog_dir=/usr/local/mysql/data //设置master 保存binlog的位置，以便MHA可以找到master的日志，我这里的也就是mysql的数据目录
candidate_master=1//设置为候选master，如果设置该参数以后，发生主从切换以后将会将此从库提升为主库。
检测各节点间ssh互信通信配置是否ok
masterha_check_ssh --conf=/etc/masterha/app1.cnf
结果：All SSH connection tests passed successfully.
检测各节点间主从复制是否ok
masterha_check_repl --conf=/etc/masterha/app1.cnf
结果：MySQL Replication Health is OK.
在验证时，若遇到这个错误：Can't exec "mysqlbinlog" ......
解决方法是在所有服务器上执行：
ln -s /usr/local/mysql/bin/* /usr/local/bin/
启动manager:
nohup /usr/bin/masterha_manager --conf=/etc/masterha/app1.cnf --remove_dead_master_conf --ignore_last_failover > /etc/masterha/manager.log 2>&1 &
--remove_dead_master_conf 为主从切换后，老的主库IP将会从配置文件中移除
--ignore_last_failover 忽略生成的切换完成文件，若不忽略，则8小时内无法再次切换
--ignore_fail_on_start
##当有slave 节点宕掉时，MHA默认是启动不了的，加上此参数即使有节点宕掉也能启动MHA，
关闭MHA：
masterha_stop --conf=/etc/masterha/app1.cnf
查看MHA状态：
masterha_check_status --conf=/etc/masterha/app1.cnf
app1 (pid:45128) is running(0:PING_OK), master:192.168.137.134
4.模拟故障转移
停掉master，
/etc/init.d/mysqld stop
查看 MHA 日志 /data/masterha/app1/manager.log
----- Failover Report -----
app1: MySQL Master failover 192.168.137.134(192.168.137.134:3306) to 192.168.137.1
30(192.168.137.130:3306) succeeded
Master 192.168.137.134(192.168.137.134:3306) is down!
Check MHA Manager logs at zifuji:/data/masterha/app1/manager.log for details.
Started automated(non-interactive) failover.
The latest slave 192.168.137.130(192.168.137.130:3306) has all relay logs for reco
very.
Selected 192.168.137.130(192.168.137.130:3306) as a new master.
192.168.137.130(192.168.137.130:3306): OK: Applying all logs succeeded.
192.168.137.146(192.168.137.146:3306): This host has the latest relay log events.
Generating relay diff files from the latest slave succeeded.
192.168.137.146(192.168.137.146:3306): OK: Applying all logs succeeded. Slave star
ted, replicating from 192.168.137.130(192.168.137.130:3306)
192.168.137.130(192.168.137.130:3306): Resetting slave info succeeded.
Master failover to 192.168.137.130(192.168.137.130:3306) completed successfully.
3. 查看slave复制状态
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: 192.168.137.130
Master_User: repl
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mysql-bin.000003