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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 1. MySQL-VIP：192.168.1.200 2. MySQL-master1：192.168.1.201 3. MySQL-master2：192.168.1.202 4. 5. OS版本：CentOS 5.4 6. MySQL版本：5.0.89 7. 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 1. MySQL> grant replication slave on *.* to 'replication'@'%' identified by 'replication'; 2. Query OK, 0 rows affected (0.00 sec) 3. 4. MySQL> show master status; 5. +------------------+----------+--------------+------------------+ 6. | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | 7. +------------------+----------+--------------+------------------+ 8. | MySQL-bin.000003 | 374 | | | 9. +------------------+----------+--------------+------------------+ 10. 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 1. 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; 2. Query OK, 0 rows affected (0.05 sec) 3. 4. MySQL> start slave; 5. Query OK, 0 rows affected (0.00 sec) 6. 7. MySQL> show slave status\G 8. *************************** 1. row *************************** 9. Slave_IO_State: Waiting for master to send event 10. Master_Host: 192.168.1.201 11. Master_User: replication 12. Master_Port: 3306 13. Connect_Retry: 60 14. Master_Log_File: MySQL-bin.000003 15. Read_Master_Log_Pos: 374 16. Relay_Log_File: MySQL-master2-relay-bin.000002 17. Relay_Log_Pos: 235 18. Relay_Master_Log_File: MySQL-bin.000003 19. Slave_IO_Running: Yes 20. Slave_SQL_Running: Yes 21. Replicate_Do_DB: 22. Replicate_Ignore_DB: 23. Replicate_Do_Table: 24. Replicate_Ignore_Table: 25. Replicate_Wild_Do_Table: 26. Replicate_Wild_Ignore_Table: 27. Last_Errno: 0 28. Last_Error: 29. Skip_Counter: 0 30. Exec_Master_Log_Pos: 374 31. Relay_Log_Space: 235 32. Until_Condition: None 33. Until_Log_File: 34. Until_Log_Pos: 0 35. Master_SSL_Allowed: No 36. Master_SSL_CA_File: 37. Master_SSL_CA_Path: 38. Master_SSL_Cert: 39. Master_SSL_Cipher: 40. Master_SSL_Key: 41. Seconds_Behind_Master: 0 42. 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 1. MySQL> grant replication slave on *.* to 'replication'@'%' identified by 'replication'; 2. Query OK, 0 rows affected (0.00 sec) 3. 4. MySQL> show master status; 5. +------------------+----------+--------------+------------------+ 6. | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | 7. +------------------+----------+--------------+------------------+ 8. | MySQL-bin.000003 | 374 | | | 9. +------------------+----------+--------------+------------------+ 10. 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 1. 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; 2. Query OK, 0 rows affected (0.05 sec) 3. 4. MySQL> start slave; 5. Query OK, 0 rows affected (0.00 sec) 6. 7. MySQL> show slave status\G 8. *************************** 1. row *************************** 9. Slave_IO_State: Waiting for master to send event 10. Master_Host: 192.168.1.202 11. Master_User: replication 12. Master_Port: 3306 13. Connect_Retry: 60 14. Master_Log_File: MySQL-bin.000003 15. Read_Master_Log_Pos: 374 16. Relay_Log_File: MySQL-master1-relay-bin.000002 17. Relay_Log_Pos: 235 18. Relay_Master_Log_File: MySQL-bin.000003 19. Slave_IO_Running: Yes 20. Slave_SQL_Running: Yes 21. Replicate_Do_DB: 22. Replicate_Ignore_DB: 23. Replicate_Do_Table: 24. Replicate_Ignore_Table: 25. Replicate_Wild_Do_Table: 26. Replicate_Wild_Ignore_Table: 27. Last_Errno: 0 28. Last_Error: 29. Skip_Counter: 0 30. Exec_Master_Log_Pos: 374 31. Relay_Log_Space: 235 32. Until_Condition: None 33. Until_Log_File: 34. Until_Log_Pos: 0 35. Master_SSL_Allowed: No 36. Master_SSL_CA_File: 37. Master_SSL_CA_Path: 38. Master_SSL_Cert: 39. Master_SSL_Cipher: 40. Master_SSL_Key: 41. Seconds_Behind_Master: 0 42. 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 1. #tar zxvf keepalived-1.1.20.tar.gz 2. #cd keepalived-1.1.20 3. #./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-164.el5-i686 4. #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 1. #mkdir /etc/keepalived 2. #vi /etc/keepalived/keepalived.conf 3. ! Configuration File for keepalived 4. global_defs { 5. notification_email { 6. luwenju@live.cn 7. } 8. notification_email_from luwenju@live.cn 9. smtp_server 127.0.0.1 10. smtp_connect_timeout 30 11. router_id MySQL-ha 12. } 13. 14. vrrp_instance VI_1 { 15. state BACKUP #两台配置此处均是BACKUP 16. interface eth0 17. virtual_router_id 51 18. priority 100 #优先级，另一台改为90 19. advert_int 1 20. 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 21. authentication { 22. auth_type PASS 23. auth_pass 1111 24. } 25. virtual_ipaddress { 26. 192.168.1.200 27. } 28. } 29. 30. virtual_server 192.168.1.200 3306 { 31. delay_loop 2 #每个2秒检查一次real_server状态 32. lb_algo wrr #LVS算法 33. lb_kind DR #LVS模式 34. persistence_timeout 60 #会话保持时间 35. protocol TCP 36. real_server 192.168.1.201 3306 { 37. weight 3 38. notify_down /usr/local/MySQL/bin/MySQL.sh #检测到服务down后执行的脚本 39. TCP_CHECK { 40. connect_timeout 10 #连接超时时间 41. nb_get_retry 3 #重连次数 42. delay_before_retry 3 #重连间隔时间 43. connect_port 3306 #健康检查端口 44. } 45. } 编写检测服务down后所要执行的脚本 1. #vi /usr/local/MySQL/bin/MySQL.sh 2. #!/bin/sh 3. pkill keepalived 4. #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 1. #/usr/local/keepalived/sbin/keepalived –D 2. #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 1. #tar zxvf keepalived-1.1.20.tar.gz 2. #cd keepalived-1.1.20 3. #./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-164.el5-i686 4. #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 1. #mkdir /etc/keepalived 2. #vi /etc/keepalived/keepalived.conf 3. ! Configuration File for keepalived 4. global_defs { 5. notification_email { 6. luwenju@live.cn 7. } 8. notification_email_from luwenju@live.cn 9. smtp_server 127.0.0.1 10. smtp_connect_timeout 30 11. router_id MySQL-ha 12. } 13. 14. vrrp_instance VI_1 { 15. state BACKUP 16. interface eth0 17. virtual_router_id 51 18. priority 90 19. advert_int 1 20. authentication { 21. auth_type PASS 22. auth_pass 1111 23. } 24. virtual_ipaddress { 25. 192.168.1.200 26. } 27. } 28. 29. virtual_server 192.168.1.200 3306 { 30. delay_loop 2 31. lb_algo wrr 32. lb_kind DR 33. persistence_timeout 60 34. protocol TCP 35. real_server 192.168.1.202 3306 { 36. weight 3 37. notify_down /usr/local/MySQL/bin/MySQL.sh 38. TCP_CHECK { 39. connect_timeout 10 40. nb_get_retry 3 41. delay_before_retry 3 42. connect_port 3306 43. } 44. } 编写检测服务down后所要执行的脚本 1. #vi /usr/local/MySQL/bin/MySQL.sh 2. #!/bin/sh 3. pkill keepalived 4. #chmod +x /usr/local/MySQL/bin/MySQL.sh 5. 6. 启动keepalived 7. #/usr/local/keepalived/sbin/keepalived –D 8. #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 1. MySQL> grant all privileges on *.* to 'root'@'%' identified by '123456'; 2. Query OK, 0 rows affected (0.00 sec) 3. 4. MySQL> flush privileges; 5. Query OK, 0 rows affected (0.00 sec) 使用客户端登录VIP测试 1. C:\MySQL\bin>MySQL.exe -uroot -p123456 -h192.168.1.200 -P3306 2. Welcome to the MySQL monitor. Commands end with ; or \g. 3. Your MySQL connection id is 224 4. Server version: 5.0.89-log Source distribution 5. 6. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. 7. 8. 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） 1. MySQL> show databases; 2. ERROR 2006 (HY000): MySQL server has gone away 3. No connection. Trying to reconnect... 4. Connection id: 592 5. Current database: *** NONE *** 6. 7. +--------------------+ 8. | Database | 9. +--------------------+ 10. | information_schema | 11. | MySQL | 12. | test | 13. +--------------------+ 14. 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。
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