关于MySQL-HA，目前有多种解决方案，比如heartbeat、drbd、mmm、共享存储，但是它们各有优缺点。heartbeat、drbd配置较为复杂，需要自己写脚本才能实现MySQL自动切换，对于不会脚本语言的人来说，这无疑是一种脑裂问题;对于mmm，生产环境中很少有人用，且mmm 管理端需要单独运行一台服务器上，要是想实现高可用，就得对mmm管理端做HA，这样无疑又增加了硬件开支;对于共享存储，个人觉得MySQL数据还是放在本地较为安全，存储设备毕竟存在单点隐患。使用MySQL双master+keepalived是一种非常好的解决方案，在MySQL-HA环境中，MySQL互为主从关系，这样就保证了两台MySQL数据的一致性，然后用keepalived实现虚拟IP，通过keepalived自带的服务监控功能来实现MySQL故障时自动切换。

　　下面，我把即将上线的一个生产环境中的架构与大家分享一下，看一下这个架构中，MySQL-HA是如何实现的，环境拓扑如下

MySQL-VIP：192.168.1.200    
MySQL-master1：192.168.1.201    
MySQL-master2：192.168.1.202    
   
OS版本：CentOS 5.4    
MySQL版本：5.0.89    
Keepalived版本：1.1.20

　　一、MySQL master-master配置

　　1、修改MySQL配置文件

　　两台MySQL均如要开启binlog日志功能，开启方法：在MySQL配置文件[MySQLd]段中加上log-bin=MySQL-bin选项

　　两台MySQL的server-ID不能一样，默认情况下两台MySQL的serverID都是1，需将其中一台修改为2即可

　　2、将192.168.1.201设为192.168.1.202的主服务器

　　在192.168.1.201上新建授权用户

MySQL> grant replication slave on *.* to 'replication'@'%' identified by 'replication';    Query OK, 0 rows affected (0.00 sec)    

MySQL> show master status;    +------------------+----------+--------------+------------------+    | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |    +------------------+----------+--------------+------------------+    | MySQL-bin.000003 |      374 |              |                  |     +------------------+----------+--------------+------------------+    1 row in set (0.00 sec)  

　　在192.168.1.202上将192.168.1.201设为自己的主服务器

MySQL> change master to master_host='192.168.1.201',master_user='replication',master_password='replication',master_log_file='MySQL-bin.000003',master_log_pos=374;    Query OK, 0 rows affected (0.05 sec)    

MySQL> start slave;    Query OK, 0 rows affected (0.00 sec)    

MySQL> show slave status\G    *************************** 1. row ***************************                 Slave_IO_State: Waiting for master to send event                    Master_Host: 192.168.1.201                    Master_User: replication                    Master_Port: 3306                  Connect_Retry: 60                Master_Log_File: MySQL-bin.000003            Read_Master_Log_Pos: 374                 Relay_Log_File: MySQL-master2-relay-bin.000002                  Relay_Log_Pos: 235          Relay_Master_Log_File: MySQL-bin.000003               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:                      Last_Errno: 0                     Last_Error:                    Skip_Counter: 0            Exec_Master_Log_Pos: 374                Relay_Log_Space: 235                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    1 row in set (0.00 sec)  

　　3、将192.168.1.202设为192.168.1.201的主服务器

　　在192.168.1.202上新建授权用户

MySQL> grant replication slave on *.* to 'replication'@'%' identified by 'replication';    Query OK, 0 rows affected (0.00 sec)    

MySQL> show master status;    +------------------+----------+--------------+------------------+    | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |    +------------------+----------+--------------+------------------+    | MySQL-bin.000003 |      374 |              |                  |     +------------------+----------+--------------+------------------+    1 row in set (0.00 sec)  

　　在192.168.1.201上，将192.168.1.202设为自己的主服务器

MySQL> change master to master_host='192.168.1.202',master_user='replication',master_password='replication',master_log_file='MySQL-bin.000003',master_log_pos=374;    Query OK, 0 rows affected (0.05 sec)    

MySQL> start slave;    Query OK, 0 rows affected (0.00 sec)    

MySQL> show slave status\G    *************************** 1. row ***************************                 Slave_IO_State: Waiting for master to send event                    Master_Host: 192.168.1.202                    Master_User: replication                    Master_Port: 3306                  Connect_Retry: 60                Master_Log_File: MySQL-bin.000003            Read_Master_Log_Pos: 374                 Relay_Log_File: MySQL-master1-relay-bin.000002                  Relay_Log_Pos: 235          Relay_Master_Log_File: MySQL-bin.000003               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:                      Last_Errno: 0                     Last_Error:                    Skip_Counter: 0            Exec_Master_Log_Pos: 374                Relay_Log_Space: 235                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    1 row in set (0.00 sec)  

　　4、MySQL同步测试

　　如上述均正确配置，现在任何一台MySQL上更新数据都会同步到另一台MySQL，MySQL同步在此不再演示

二、keepalived安装及配置

　　1、192.168.1.201服务器上keepalived安装及配置

　　安装keepalived

#tar zxvf keepalived-1.1.20.tar.gz    #cd keepalived-1.1.20    #./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-164.el5-i686    #make && make install  

　　配置keepalived

　　我们自己在新建一个配置文件，默认情况下keepalived启动时会去/etc/keepalived目录下找配置文件

#mkdir /etc/keepalived    #vi /etc/keepalived/keepalived.conf    ! Configuration File for keepalived    global_defs {         notification_email {         luwenju@live.cn         }         notification_email_from luwenju@live.cn         smtp_server 127.0.0.1         smtp_connect_timeout 30         router_id MySQL-ha         }    

vrrp_instance VI_1 {         state BACKUP   #两台配置此处均是BACKUP         interface eth0         virtual_router_id 51         priority 100   #优先级，另一台改为90         advert_int 1         nopreempt  #不抢占，只在优先级高的机器上设置即可，优先级低的机器不设置         authentication {         auth_type PASS         auth_pass 1111         }         virtual_ipaddress {         192.168.1.200         }         }    

virtual_server 192.168.1.200 3306 {         delay_loop 2   #每个2秒检查一次real_server状态         lb_algo wrr   #LVS算法         lb_kind DR    #LVS模式         persistence_timeout 60   #会话保持时间         protocol TCP         real_server 192.168.1.201 3306 {         weight 3         notify_down /usr/local/MySQL/bin/MySQL.sh  #检测到服务down后执行的脚本         TCP_CHECK {         connect_timeout 10    #连接超时时间         nb_get_retry 3       #重连次数         delay_before_retry 3   #重连间隔时间         connect_port 3306   #健康检查端口         }         }  

　　编写检测服务down后所要执行的脚本

#vi /usr/local/MySQL/bin/MySQL.sh    #!/bin/sh    pkill keepalived    #chmod +x /usr/local/MySQL/bin/MySQL.sh  

　　注：此脚本是上面配置文件notify_down选项所用到的，keepalived使用notify_down选项来检查real_server的服务状态，当发现real_server服务故障时，便触发此脚本;我们可以看到，脚本就一个命令，通过pkill keepalived强制杀死keepalived进程，从而实现了MySQL故障自动转移。另外，我们不用担心两个MySQL会同时提供数据更新操作，因为每台MySQL上的keepalived的配置里面只有本机MySQL的IP+VIP，而不是两台MySQL的IP+VIP

　　启动keepalived

#/usr/local/keepalived/sbin/keepalived –D    #ps -aux | grep keepalived  

　　测试

　　找一台局域网PC，然后去ping MySQL的VIP，这时候MySQL的VIP是可以ping的通的

　　停止MySQL服务，看keepalived健康检查程序是否会触发我们编写的脚本

　　2、192.168.1.202上keepalived安装及配置

　　安装keepalived

#tar zxvf keepalived-1.1.20.tar.gz    #cd keepalived-1.1.20    #./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-164.el5-i686    #make && make install  

　　配置keepalived

　　这台配置和上面基本一样，但有三个地方不同：优先级为90、无抢占设置、real_server为本机IP

#mkdir /etc/keepalived    #vi /etc/keepalived/keepalived.conf    ! Configuration File for keepalived    global_defs {         notification_email {         luwenju@live.cn         }         notification_email_from luwenju@live.cn         smtp_server 127.0.0.1         smtp_connect_timeout 30         router_id MySQL-ha         }    

vrrp_instance VI_1 {         state BACKUP         interface eth0         virtual_router_id 51         priority 90         advert_int 1         authentication {         auth_type PASS         auth_pass 1111         }         virtual_ipaddress {         192.168.1.200         }         }    

virtual_server 192.168.1.200 3306 {         delay_loop 2         lb_algo wrr         lb_kind DR         persistence_timeout 60         protocol TCP         real_server 192.168.1.202 3306 {         weight 3         notify_down /usr/local/MySQL/bin/MySQL.sh         TCP_CHECK {         connect_timeout 10         nb_get_retry 3         delay_before_retry 3         connect_port 3306         }         }   

　　编写检测服务down后所要执行的脚本

#vi /usr/local/MySQL/bin/MySQL.sh    #!/bin/sh    pkill keepalived    #chmod +x /usr/local/MySQL/bin/MySQL.sh    

启动keepalived    #/usr/local/keepalived/sbin/keepalived –D    #ps -aux | grep keepalived 

　　测试

　　●停止MySQL服务，看keepalived健康检查程序是否会触发我们编写的脚本

　　三、测试

　　● MySQL远程登录测试

　　我们找一台安装有MySQL客户端的windows，然后登录VIP，看是否能登录，在登录之两台MySQL服务器都要授权允许从远程登录

MySQL> grant all privileges on *.* to 'root'@'%' identified by '123456';    Query OK, 0 rows affected (0.00 sec)    

MySQL> flush privileges;    Query OK, 0 rows affected (0.00 sec)   

　　使用客户端登录VIP测试

C:\MySQL\bin>MySQL.exe -uroot -p123456 -h192.168.1.200 -P3306    Welcome to the MySQL monitor.  Commands end with ; or \g.    Your MySQL connection id is 224    Server version: 5.0.89-log Source distribution    

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.    

MySQL>   

　　● keepalived故障转移测试

　　※在windows客户端一直去ping VIP，然后关闭192.168.1.201上的keepalived，正常情况下VIP就会切换到192.168.1.202上面去

　　※开启192.168.1.201上的keepalived，关闭192.168.1.202上的keepalived，看是否能自动切换，正常情况下VIP又会属于192.168.1.201

　　注：keepalived切换速度还是非常块的，整个切换过程只需1-3秒

　　● MySQL故障转移测试

　　※在192.168.1.201上关闭MySQL服务，看VIP是否会切换到192.168.1.202上

　　※开启192.168.1.201上的MySQL和keepalived，然后关闭192.168.1.202上的MySQL，看VIP是否会切换到192.168.1.201上

　　下面是用windows客户端连接的MySQL的VIP，在切换时我执行了一个MySQL查询命令，从执行show databases到显示出结果时间为3-5秒(大家可以看到上面有个错误提示，不过不用担心，因为我们的keepalived切换大概为3秒左右，这3秒左右VIP是谁都不属于的)

MySQL> show databases;    ERROR 2006 (HY000): MySQL server has gone away    No connection. Trying to reconnect...    Connection id:    592    Current database: *** NONE ***    

+--------------------+    | Database           |    +--------------------+    | information_schema |    | MySQL              |    | test               |    +--------------------+    3 rows in set (9.01 sec)   

　　后话：世间万事万物，都不具备绝对的完美，就像上面的MySQL-HA一样，keepalived只能做到对3306的健康检查，但是做不到比如像MySQL复制中的slave-SQL、slave-IO进程的检查。所以要想做到一些细致的健康检查，还得需要借助额外的监控工具，比如nagios，然后用nagios实现短信、邮件报警，从而能够有效地解决问题。