使用keepalived构建高可用mysql-HA
作者：陆文举 2010-11-28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、mysqlmaster-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:
Replcate_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
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';
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 tomaster_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;
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_B:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wid_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
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
编写检测服务down后所要执行的脚本
#vi /usr/local/mysql/bin/mysql.sh
#!/bin/sh
pkillkeepalived#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_timeout60
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/shpkillkeepalived
#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。在此再次感谢守住兄弟及师父不厌其烦的帮助与指点