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。
source : http://database.51cto.com/art/201012/237204.htm
