LVS有三种工作模式，分别是DR(Direct Routing 直接路由)、TUN(Tunneling IP隧道)、NAT(Network Address Translation 网络地址转换)。其中TUN模式能够支持更多的Real Server，但需要所有服务器支持IP隧道协议；DR也可以支持相当的Real Server，但需要保证Director Server虚拟网卡与物理网卡在同一网段；NAT扩展性有限，无法支持更多的Real Server，因为所有的请求包和应答包都需要Director Server进行解析再生，影响效率。 同时，LVS负载均衡有10中调度算法，分别是rr、wrr、lc、wlc、lblc、lblcr、dh、sh、sed、nq(详细介绍本文不在说明)
本文中将利用LVS实现MySQL的读写负载均衡，Keepalived避免节点出现单点故障。
LVS+Keepalived配置
环境准备
LVS1：172.30.8.192
LVS2：172.30.8.193
MySQL Server1：172.30.8.190
MySQL Server2：172.30.8.191
VIP：172.30.8.200
OS: CentOS 6.5
Mysql安装及双主配置
MySQL：5.1.73
本文为了方便直接采用的yum安装方式安装将不在介绍
全局配置(即MAster，Slave都需配置)
1)修改配置文件
#vim /etc/my.cnf
添加
log-bin=mysql-bin
server-id=190
修改完需要重启数据库
注：server-id是唯一id一般都采用ip末尾
2)分配复制权限，主库和从库均需要执行
mysql> grant replication client,replication slave on *.* to root@'172.30.8.%' identified by 'root';
Query OK,0 rows affected (0.00 sec)
2)清空日志文件，主从库都是默认开启二进制日志文件
mysql>show binary logs;+------------------+-----------+
| Log_name | File_size |
+------------------+-----------+
| mysql-bin.000001 | 26636 |
| mysql-bin.000002 | 1069399 |
| mysql-bin.000003 | 26636 |
| mysql-bin.000004 | 1069399 |
| mysql-bin.000005 | 536 |
+------------------+-----------+
5 rows in set (0.00sec)
mysql>reset master;
Query OK,0 rows affected (0.01sec)
mysql>show binary logs;+------------------+-----------+
| Log_name | File_size |
+------------------+-----------+
| mysql-bin.000001 | 107 |
+------------------+-----------+
1 row in set (0.00 sec)
需要注意的是，如果不想清空日志文件的话，需要记录当前master的log_file和log_pos，并在下面启用复制操作时指定这两个参数或者在slave的配置文件指定。
Slave配置
1)启用复制
让slave连接master并开始重做master二进制日志中的事件
mysql> change master to master_host='172.30.8.190',master_user='root',master_password='1231234',master_port=3306,master_log_file='mysql-bin.000001',master_log_pos=107;
master_log_pos如果是日志的开始位置值可以为0；master_log_file是初始日志文件。如果master日志没有被清空，这里就是当前master的日志信息
要注意的是，默认情况下，会同步该用户下所有的DB，如果想限定哪些DB，有3种思路
在master上的/etc/my.inf中通过参数binlog-do-db、binlog-ignore-db设置需要同步的数据库。
在执行grant分配权限操作的时候，限定数据库
在slave上限定数据库使用replicate-do-db=dbname
2)开启slave
mysql>start slave;
Query OK,0 rows affected (0.00 sec)
3)确认Slave是否和Mater成功通信。如果 Slave_IO_Running和Slave_SQL_Running都是yes，则证明配置成功
mysql>show slave status\G;*************************** 1. row ***************************Slave_IO_State: Waitingfor master to send eventMaster_Host:172.30.8.190Master_User: root
Master_Port:3306Connect_Retry:60Master_Log_File: mysql-bin.000001Read_Master_Log_Pos:1042Relay_Log_File: mysqld-relay-bin.000020Relay_Log_Pos:510Relay_Master_Log_File: mysql-bin.000001Slave_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:0Last_Error:
Skip_Counter:0Exec_Master_Log_Pos:1042Relay_Log_Space:811Until_Condition: None
Until_Log_File:
Until_Log_Pos:0Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master:0Master_SSL_Verify_Server_Cert: No
Last_IO_Errno:0Last_IO_Error:
Last_SQL_Errno:0Last_SQL_Error:1 row in set (0.00sec)
ERROR:
No query specified
至此mysql主从配置完毕，如果双主则操作相反即可。
附加：
1)mysql修改密码
mysql>use mysql;
Reading table informationforcompletion of table and column names
You can turn offthis feature to get a quicker startup with -A
Database changed
mysql> update user set password=password("1231234") where user="root";
Query OK,5 rows affected (0.00sec)
Rows matched:5 Changed: 5 Warnings: 0mysql>flush privileges;
Query OK,0 rows affected (0.00 sec)
2)授权远程连接
mysql>GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTIFIED BY '1231234' WITH GRANT OPTION;
同步测试
1)Master创建数据库
mysql>create database jingzi;
Query OK,1 row affected (0.00sec)
mysql>show databases;+--------------------+
| Database |
+--------------------+
| information_schema |
| jingzi |
| mysql |
| test |
+--------------------+
4 rows in set (0.00 sec)
2)slave查看
mysql>show databases;+--------------------+
| Database |
+--------------------+
| information_schema |
| jingzi |
| mysql |
| test |
+--------------------+
4 rows in set (0.00 sec)
通过以上验证，可以看到主服务器上的修改能够正常同步到从服务器。
Keepalived安装及LVS安装(以下操作在lvs服务器主+从上操作)
Keepalived安装
需要安装以下软件包
#yum install -y kernel-devel openssl openssl-devel gcc* (如果后边编译报错缺少什么包安装什么包就ok了)
安装
#wget http://www.keepalived.org/software/keepalived-1.2.13.tar.gz
#tar-zxvf keepalived-1.2.13.tar.gz
#cd keepalived-1.2.13#./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.32-431.5.1.el6.x86_64/
默认情况下keepalived启动时会去/etc/keepalived目录下找配置文件，将需要的配置文件拷贝到指定位置
# mkdir /etc/keepalived
#cp/usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/rc.d/init.d/
#cp/usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
#cp/usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/#cp/usr/local/keepalived/sbin/keepalived /usr/sbin/#chkconfig keepalived on
LVS安装
需要安装以下软件包
#yum install -y libnl* popt* kernel-headers popt-static
查看是否加载lvs模块
#modprobe -l |grep ipvs
解压安装
#ln -s /usr/src/kernels/2.6.32-431.5.1.el6.x86_64/ /usr/src/linux
#tar-zxvf ipvsadm-1.26.tar.gz
#make&& make install
LVS安装完成，查看当前LVS集群
#ipvsadm -ln
至此keppalived+lvs安装完成接下来我们进行配置
LVS+Keepalived配置(以下操作是在lvs-1上执行lvs-2类似)
配置Keepalived
修改keepalived配置文件并添加以下代码
[root@lvs-1 ~]# vim /etc/keepalived/keepalived.conf
global_defs {
router_id LVS_1 # 设置lvs的id，在一个网络内应该是唯一的
}
vrrp_instance VI_1 {
state MASTER #指定Keepalived的角色，MASTER为主，BACKUP为备interfaceeth0 #虚拟ip所在网
virtual_router_id51#虚拟路由编号，主备要一致
priority100#定义优先级，数字越大，优先级越高，主DR必须大于备用DR
advert_int1#检查间隔，默认为1s
authentication {
auth_type PASS
auth_pass1111}
virtual_ipaddress {172.30.8.200 #定义虚拟IP(VIP)为172.30.8.200，可多设，每行一个
}
}
# 定义对外提供服务的LVS的VIP以及port
virtual_server172.30.8.200 3306{
delay_loop6# 设置健康检查时间，单位是秒
lb_algo wlc # 设置负载调度的算法为wlc 基于权重的调度算法
lb_kind DR # 设置LVS实现负载的机制，有NAT、TUN、DR三个模式
nat_mask255.255.255.0persistence_timeout 50会话保持时间 (为了实验效果可以注释掉该选项)
protocol TCP
real_server172.30.8.190 3306{ # 指定real server1的IP地址
weight3# 配置节点权值，数字越大权重越高
TCP_CHECK {
connect_timeout10nb_get_retry3delay_before_retry3connect_port3306}
}
real_server172.30.8.191 3306{ # 指定real server2的IP地址
weight3# 配置节点权值，数字越大权重越高
TCP_CHECK {
connect_timeout10nb_get_retry3delay_before_retry3connect_port3306}
}
}
注意lvs-2操作类似只需修改以下选项即可
1.state MASTER #指定Keepalived的角色，MASTER为主，BACKUP为备
改为
state BACKUP #指定Keepalived的角色，MASTER为主，BACKUP为备2.priority 100#定义优先级，数字越大，优先级越高，主DR必须大于备用DR
改为
priority99 #定义优先级，数字越大，优先级越高，主DR必须大于备用DR
配置LVS(此脚本需要添加到lvs-1，Mysql-master，Mysql-slave)
编写LVS启动脚本/etc/init.d/realserver
[root@lvs-1 ~]# vim /etc/init.d/realserver
SNS_VIP=172.30.8.200
/etc/rc.d/init.d/functionscase "$1" instart)
ifconfig lo:0 $SNS_VIP netmask 255.255.255.255broadcast $SNS_VIP/sbin/route add -host $SNS_VIP dev lo:0echo"1" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo"2" >/proc/sys/net/ipv4/conf/lo/arp_announce
echo"1" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo"2" >/proc/sys/net/ipv4/conf/all/arp_announce
sysctl-p >/dev/null 2>&1echo"RealServer Start OK";;
stop)
ifconfig lo:0down
route del $SNS_VIP>/dev/null 2>&1echo"0" >/proc/sys/net/ipv4/conf/lo/arp_ignore
echo"0" >/proc/sys/net/ipv4/conf/lo/arp_announce
echo"0" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo"0" >/proc/sys/net/ipv4/conf/all/arp_announce
echo"RealServer Stoped";;*)
echo"Usage: $0 {start|stop}"exit1esac
exit0
将lvs脚本加入开机自启动
#chmod +x /etc/init.d/realserver
#echo"/etc/init.d/realserver" >> /etc/rc.d/rc.local
分别启动LVS和keepalived
# service realserver start
# service keepalived start
注意此时网卡的变化，可以看到虚拟网卡已经分配到了realserver上。
此时查看LVS集群状态，可以看到集群下有两个Real Server，调度算法，权重等信息。ActiveConn代表当前Real Server的活跃连接数
[root@lvs-1 ~]# ipvsadm -ln
IP Virtual Server version1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags->RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP172.30.8.200:3306wlc-> 172.30.8.190:3306 Route 3 0 0
-> 172.30.8.191:3306 Route 3 0
测试验证
关闭MySQL Server2
[root@mysql-2 ~]# service mysqld stop
Stopping mysqld: [ OK ]
在LVS1查看/var/log/messages中关于keepalived日志，LVS1检测到了MySQL Server2宕机，同时LVS集群自动剔除了故障节点
May 18 23:52:26 localhost Keepalived_healthcheckers[5909]: TCP connection to [172.30.8.191]:3306 failed !!!May18 23:52:26 localhost Keepalived_healthcheckers[5909]: Removing service [172.30.8.191]:3306 from VS [172.30.8.200]:3306
从新启动MySQL Server2后自动将故障节点自动加入LVS集群
May 18 23:53:50 localhost Keepalived_healthcheckers[5909]: TCP connection to [172.30.8.191]:3306success.
May18 23:53:50 localhost Keepalived_healthcheckers[5909]: Adding service [172.30.8.191]:3306 to VS [172.30.8.200]:3306
关闭LVS1上的Keepalived(模拟宕机操作)，查看LVS1上的日志，可以看到Keepalived移出了LVS1上的VIP
May 18 23:54:28 localhost Keepalived[5908]: Stopping Keepalived v1.2.13 (05/17,2017)
May18 23:54:28 localhost Keepalived_vrrp[5910]: VRRP_Instance(VI_1) sending 0priority
May18 23:54:28 localhost Keepalived_vrrp[5910]: VRRP_Instance(VI_1) removing protocol VIPs.
May18 23:54:28 localhost Keepalived_healthcheckers[5909]: Netlink reflector reports IP 172.30.8.200removed
May18 23:54:28 localhost Keepalived_healthcheckers[5909]: Removing service [172.30.8.190]:3306 from VS [172.30.8.200]:3306May18 23:54:28 localhost Keepalived_healthcheckers[5909]: Removing service [172.30.8.191]:3306 from VS [172.30.8.200]:3306
同时查看LVS2上日志，可以看到LVS2成为了Master，并接管了VIP
May 18 23:54:29 localhost Keepalived_vrrp[5187]: VRRP_Instance(VI_1) Transition to MASTER STATE
May18 23:54:30 localhost Keepalived_vrrp[5187]: VRRP_Instance(VI_1) Entering MASTER STATE
May18 23:54:30 localhost Keepalived_vrrp[5187]: VRRP_Instance(VI_1) setting protocol VIPs.
May18 23:54:30 localhost Keepalived_healthcheckers[5186]: Netlink reflector reports IP 172.30.8.200added
May18 23:54:30 localhost Keepalived_vrrp[5187]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 172.30.8.200May18 23:54:35 localhost Keepalived_vrrp[5187]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 172.30.8.200
在LVS2上查看LVS集群状态，一切正常
[root@lvs-2 ~]# ipvsadm -ln
IP Virtual Server version1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags->RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP172.30.8.200:3306wlc-> 172.30.8.190:3306 Route 3 0 0
-> 172.30.8.191:3306 Route 3 1 0
总结
MySQL主主复制是集群的基础，组成Server Array，其中每个节点作为Real Server。
LVS服务器提供了负载均衡的作用，将用户请求分发到Real Server，一台Real Server故障并不会影响整个集群的。
Keepalived搭建主备LVS服务器，避免了LVS服务器的单点故障，出现故障时可以自动切换到正常的节点。