MySql:利用keepalived构建高可用MySQL-HA

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。