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 inset (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 inset (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。