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) 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。