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。
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