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在企业中，一般系统架构的瓶颈会出现在数据库这一部分，Mysql主从架构在很大程度上解决了这部分瓶颈，但是在Mysql主从同步的架构也存在很多问题。比如：
1. 关于数据写入部分(也就是主库)往往很难做到扩展，虽然很多大公司在逻辑业务方面就进行对数据的拆分，比如商品库存按照区域去拆分(一个区域走一个库存也就是一个主库,然后定时同步总的库存)，按照商品类型去划分(一个类型的商品走一套数据库)，但是这对于很多中小型公司来说实现起来还是比较困难的；
2. 主从同步一般都是一个主库，一旦主库出现问题,就有可能直接导致整个主从同步架构崩盘，虽然发现后也是可以慢慢恢复的，但是这个恢复时间对于很多公司来说是难以接受的。
今天的这篇博文主要给解决主库单点故障这个问题提供一个思路：
- 一台主库(我们称之为master-01)提供服务,只负责数据的写入；
- 拿出一台数据库服务器(我们称之为Master-02)资源做master-01主库的从库(之间做主从同步)；
- 两台主库之间做高可用,可以采用keepalived等方案(一定要保证master-01同时也要作为keepalived的主)；
- 程序在调用主库IP地址的地方写为高可用的VIP地址；
- 所有提供服务的从服务器与master-02进行主从同步；
- 建议采用高可用策略的时候,当master-01出现问题切换到master-02的时候,即使master-01恢复了,也不要让它去自动承接VIP地址,否则可能造成数据的混写
这样做可以在一定程度上保证主库的高可用，在一台主库down掉之后,可以在极短的时间内切换到另一台主库上(尽可能减少主库宕机对业务造成的影响)，减少了主从同步给线上主库带来的压力；但是也有几个不足的地方：
- master-02可能会一直处于空闲状态(其实完全可以让它承担一部分从库的角色来负责一部分查询请求的)；
- 这样真正提供服务的从库要等master-02先同步完了数据后才能去master-02上去同步数据，这样可能会造成一定程度的同步延迟时间的加长；
- 如果master-01一旦恢复正常，会不会导致数据写入混乱(这个可以在keepalived中设置响应的规则,让其不”夺权”，我们认为的去调整操作即可。
架构的简易图如下：
方案简介
由keepalive实现VIP转移，从而实现高可用
软件环境
OS Version：Red Hat Enterprise Linux Server>
MySQL Version: MySQL-server-5.6.21-1.el6.x86_64
KeepAlived Version: keepalived-1.2.13
DownLoad URL:http://www.keepalived.org/software/keepalived-1.2.13.tar.gz
部署步骤
1) 配置MySQL主主
详细步骤省略…………..
Master A>show processlist\G
*************************** 1. row ***************************
Id: 1
User: system user
Host:
db: NULL
Command: Connect
Time: 9654
State: Slave has read all> Info: NULL
*************************** 2. row ***************************
> User: system user
Host:
db: NULL
Command: Connect
Time: 12773
State: Waiting for master to send event
Info: NULL
*************************** 3. row ***************************
> User: slave
Host: 192.168.56.102:34325
db: NULL
Command: Binlog Dump
Time: 9678
State: Master has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
Master B>show processlist \G
*************************** 1. row ***************************
> User: system user
Host:
db: NULL
Command: Connect
Time: 9771
State: Waiting for master to send event
Info: NULL
*************************** 2. row ***************************
> User: system user
Host:
db: NULL
Command: Connect
Time: 9770
State: Slave has read all> Info: NULL
*************************** 3. row ***************************
> User: slave
Host: 192.168.56.101:46709
db: NULL
Command: Binlog Dump
Time: 9746
State: Master has sent all binlog to slave; waiting for binlog to be updated
Info: NULL
2) 安装KeepAlived
#A和B主机都安装
]# tar -zxvf keepalived-1.2.13.tar.gz -C /opt/
]# cd /opt/keepalived-1.2.13/
]# mkdir /usr/local/keepalived
]# ./configure --prefix=/usr/local/keepalived/
]# make;make install
问题:configure报错
configure: error:
!!! OpenSSL is not properly installed on your system. !!!
!!! Can not include OpenSSL headers files. !!!
]# rpm -ivh keyutils-libs-devel-1.4-4.el6.x86_64.rpm
]# rpm -ivh libcom_err-devel-1.41.12-12.el6.x86_64.rpm
]# rpm -ivh pkgconfig-0.23-9.1.el6.x86_64.rpm
]# rpm -ivh libselinux-devel-2.0.94-5.3.el6.x86_64.rpm
]# rpm -ivh krb5-devel-1.9-33.el6.x86_64.rpm
]# rpm -ivh zlib-devel-1.2.3-27.el6.x86_64.rpm
]# rpm -ivh openssl-devel-1.0.0-20.el6_2.5.x86_64.rpm
3) 配置KeepAlived
Create Control File
默认情况下keepalived启动时会去/etc/keepalived目录下找配置文件
#A主机和B主机都操作
]# mkdir /etc/keepalived
#cp安装生成的conf模板到/etc/keepalived
]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
Master A配置
a) Master A配置文件
#Master A配置文件
~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
#全局配置
global_defs {
#表示keepalived在发生诸如切换操作时发送Email给哪些地址，邮件地址可以多个，每行一个
notification_email {
jixiang.yu@trekiz.com
}
#表示发送通知邮件时邮件源地址是谁
notification_email_from Alexandre.Cassen@firewall.loc
#表示发送email时使用的smtp服务器地址，这里可以用本地的sendmail来实现
smtp_server 127.0.0.1
#连接smtp连接超时时间
smtp_connect_timeout 30
#机器标识
router_id MySQL_HA
}
vrrp_instance MySQL-HA{
state BACKUP #state指定instance的初始状态，但这里指定的不算，还是得通过优先级竞选来确定。两台配置此处均是BACKUP。
interface eth1 #实例绑定的网卡，因为在配置虚拟IP的时候必须是在已有的网卡上添加的
virtual_router_id 51 #这里设置VRID，这里非常重要，相同的VRID为一个组，他将决定多播的MAC地址
priority 100 #设置本节点的优先级，优先级高的为master，如另外一个节点配置为90，那此节点就是master
advert_int 1 #检查间隔，默认为1秒
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 { #这里设置的就是VIP，也就是虚拟IP地址
192.168.56.111
}
}
virtual_server 192.168.56.111 3306{
delay_loop 2 #每个2秒检查一次real_server状态
lb_algo wrr
lb_kind DR
persistence_timeout 50 #会话保持时间
protocol TCP
real_server 192.168.56.101 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 3 #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
}
}
}
b) Master A编写notify_down脚本
~]# mkdir -p /usr/local/MySQL/bin/
~]# vim /usr/local/MySQL/bin/MySQL.sh
#!/bin/sh
pkill keepalived
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
c) Master A启动KeepAlived服务
~]# /usr/local/keepalived/sbin/keepalived –D
~]# ps aux|grep keep
root 29423 0.0 0.1 39484 764 ? Ss 20:27 0:00 /usr/local/keepalived/sbin/keepalived -D
root 29424 0.0 0.4 43660 2056 ? S 20:27 0:00 /usr/local/keepalived/sbin/keepalived -D
root 29425 0.0 0.2 43660 1368 ? S 20:27 0:00 /usr/local/keepalived/sbin/keepalived -D
root 29439 0.0 0.1 103240 840 pts/2 S+ 20:27 0:00 grep keep
#可以看到VIP已经飘在eth1上
~]# ip a|grep eth1
3: eth1:< BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
inet 192.168.56.101/24 brd 192.168.56.255 scope global eth1
inet 192.168.56.111/32 scope global eth1
d) Master A测试keepalived服务
#停止MySQL服务
~]# /etc/init.d/mysql stop
Shutting down MySQL..... [ OK ]
#查看vip，发现VIP已经不存在
~]# ip a|grep eth1
3: eth1:< BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
inet 192.168.56.101/24 brd 192.168.56.255 scope global eth1
#查看keepalive进程消失
~]# ps -ef|grep keep
root 29537 4894 0 20:34 pts/2 00:00:00 grep keep
#监控日志
~]# tail -f /var/log/messages
Dec 3 20:34:08 MySQL1 Keepalived_healthcheckers[29424]: TCP connection to [192.168.56.101]:3306 failed !!!
Dec 3 20:34:08 MySQL1 Keepalived_healthcheckers[29424]: Removing service [192.168.56.101]:3306 from VS [192.168.56.111]:3306
Dec 3 20:34:08 MySQL1 Keepalived_healthcheckers[29424]: Executing [/usr/local/MySQL/bin/MySQL.sh] for service [192.168.56.101]:3306 in VS [192.168.56.111]:3306
Dec 3 20:34:08 MySQL1 Keepalived_healthcheckers[29424]: Lost quorum 1-0=1 > 0 for VS [192.168.56.111]:3306
Dec 3 20:34:08 MySQL1 Keepalived_healthcheckers[29424]: Remote SMTP server [127.0.0.1]:25 connected.
Dec 3 20:34:09 MySQL1 Keepalived[29423]: Stopping Keepalived v1.2.13 (12/03,2014)
Dec 3 20:34:09 MySQL1 Keepalived_vrrp[29425]: VRRP_Instance(MySQL-HA{) sending 0 priority
Dec 3 20:34:09 MySQL1 Keepalived_vrrp[29425]: VRRP_Instance(MySQL-HA{) removing protocol VIPs.
Dec 3 20:34:09 MySQL1 Keepalived_healthcheckers[29424]: Netlink reflector reports IP 192.168.56.111 removed
Dec 3 20:34:09 MySQL1 avahi-daemon[1430]: Server startup complete. Host name is MySQL1-62.local. Local service cookie is 1197773774.
Dec 3 20:34:09 MySQL1 avahi-daemon[1430]: Withdrawing address record for 192.168.56.111 on eth1.
Dec 3 20:34:10 MySQL1 avahi-daemon[1430]: Service "MySQL1-62" (/services/ssh.service) successfully established.
Master B配置
a) Master B配置文件
#跟DB1基本一致，但有三个地方不同：优先级为90、无抢占设置、real_server为本机IP
DB2~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
jixiang.yu@trekiz.com
}
notification_email_from jixiang.yu@trekiz.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id MySQL_HA
}
vrrp_instance MySQL-HA{
state BACKUP
interface eth1
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.56.111
}
}
virtual_server 192.168.56.111 3306{
delay_loop 2
lb_algo wrr
lb_kind DR
persistence_timeout 50
protocol TCP
real_server 192.168.56.102 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 #健康检查端口
}
}
}
b) Master B编写notify_down脚本
~]# mkdir -p /usr/local/MySQL/bin/
~]# vim /usr/local/MySQL/bin/MySQL.sh
#!/bin/sh
pkill keepalived
c) Master B启动KeepAlived服务
~]# /usr/local/keepalived/sbin/keepalived –D
~]# ps aux|grep keep
root 2855 0.0 0.1 39484 764 ? Ss 09:56 0:00 /usr/local/keepalive/sbin/keepalived -D
root 2856 0.0 0.3 41588 1992 ? S 09:56 0:00 /usr/local/keepalive/sbin/keepalived -D
root 2857 0.0 0.2 41588 1288 ? S 09:56 0:00 /usr/local/keepalive/sbin/keepalived -D
root 2865 0.0 0.1 103240 840 pts/2 S+ 09:56 0:00 grep keep
#可以看到VIP已经飘在eth1上
~]# ip a|grep eth1
3: eth1:< BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
inet 192.168.56.102/24 brd 192.168.56.255 scope global eth1
inet 192.168.56.111/32 scope global eth1
d) Master B测试keepalived服务
#停止MySQL服务
~]# /etc/init.d/mysql stop
Shutting down MySQL..... [ OK ]
#查看vip，发现VIP已经不存在
~]# ip a|grep eth1
3: eth1:< BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
inet 192.168.56.101/24 brd 192.168.56.255 scope global eth1
#查看keepalive进程消失
~]# ps -ef|grep keep
root 29537 4894 0 20:34 pts/2 00:00:00 grep keep
#监控日志
~]# tail -f /var/log/messages
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: TCP connection to [192.168.56.102]:3306 failed !!!
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: Removing service [192.168.56.102]:3306 from VS [192.168.56.111]:3306
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: Executing [/usr/local/MySQL/bin/MySQL.sh] for service [192.168.56.102]:3306 in VS [192.168.56.111]:3306
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: Lost quorum 1-0=1 > 0 for VS [192.168.56.111]:3306
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: Remote SMTP server [127.0.0.1]:25 connected.
Dec 4 10:35:53 MySQL2 Keepalived[6732]: Stopping Keepalived v1.2.13 (11/24,2014)
Dec 4 10:35:53 MySQL2 Keepalived_vrrp[6734]: VRRP_Instance(MySQL-HA{) sending 0 priority
Dec 4 10:35:53 MySQL2 Keepalived_vrrp[6734]: VRRP_Instance(MySQL-HA{) removing protocol VIPs.
Dec 4 10:35:53 MySQL2 Keepalived_healthcheckers[6733]: Netlink reflector reports IP 192.168.56.111 removed
Dec 4 10:35:54 MySQL2 avahi-daemon[1387]: Withdrawing address record for 192.168.56.111 on eth1.
4) MySQL Client使用VIP连接数据库
~]# mysql -u trekiz -h 192.168.56.111 -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection> Server version: 5.6.21-log MySQL Community Server (GPL)
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
5) 配置init.d/keepalived脚本
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/sbin/keepalived /sbin/
~]# /etc/init.d/keepalived -h
Usage: /etc/init.d/keepalived {start|stop|reload|restart|condrestart|status}
6) KeepAlived Failover Test
a) Master A,B都启动keepalived,vip在A上,此时A主机pkill keepalived
mysql> show master status;
+---------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------------+----------+--------------+------------------+-------------------+
| master_slave.000031 | 532 | | | |
+---------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
mysql> show master status;
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql> show master status;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection> Current database: *** NONE ***
+-----------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-----------------+----------+--------------+------------------+-------------------+
| master_a.000021 | 532 | | | |
+-----------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
结果
VIP就会切换到Master B上面去
b) 启动Master A的keepalived,vip在B上,B主机pkill keepalived
mysql> show master status;
+-----------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-----------------+----------+--------------+------------------+-------------------+
| master_a.000021 | 532 | | | |
+-----------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)
mysql> show master status;
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql> show master status;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection> Current database: *** NONE ***
+---------------------+----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+---------------------+----------+--------------+------------------+-------------------+
| master_slave.000031 | 532 | | | |
+---------------------+----------+--------------+------------------+-------------------+
1 row in set (0.08 sec)
结果
VIP就会切换到Master A上面去
c) Master A,B都启动keepalived,vip在A上,此时A主机stop mysql
结果
VIP就会切换到Master B上面去
d) 启动Master A的keepalived,vip在B上,B主机stop mysql
结果
VIP就会切换到Master A上面去
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