MySQL 主主复制 + LVS + Keepalived 实现 MySQL 高可用性

MySQL复制能够保证数据的冗余的同时可以做读写分离来分担系统压力,如果是主主复制还可以很好的避免主节点的单点故障。但是MySQL主主复制存在一些问题无法满足我们的实际需要:未提供统一访问入口来实现负载均衡,如果其中master宕掉的话需要手动切换到另外一个master,而不能自动进行切换。

这篇文章下面要介绍如何通过LVS+Keepalived的方式来是实现MySQL的高可用性,同时解决以上问题。

Keepalived和LVS介绍

Keepalived是一个基于VRRP(虚拟路由冗余协议)可用来实现服务高可用性的软件方案,避免出现单点故障。Keepalived一般用来实现轻量级高可用性,且不需要共享存储,一般用于两个节点之间,常见有LVS+Keepalived、Nginx+Keepalived组合。

LVS(Linux Virtual Server)是一个高可用性虚拟的服务器集群系统。本项目在1998年5月由章文嵩博士成立,是中国国内最早出现的自由软件项目之一。

LVS主要用于多服务器的负载均衡,作用于网络层。LVS构建的服务器集群系统中,前端的负载均衡层被称为Director Server;后端提供服务的服务器组层被称为Real Server。通过下图可以大致了解LVS的基础架构。

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

详细的LVS说明请参见 传送门

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

LVS1:192.168.1.2

LVS2:192.168.1.11

MySQL Server1:192.168.1.5

MySQL Server2:192.168.1.6

VIP:192.168.1.100

OS: CentOS 6.4

Keepalive安装

keepalived下载地址

需要安装以下软件包

# yum install -y kernel-devel openssl openssl-devel

解压keepalived到/usr/local/并进入目录执行配置编译

# ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.32-431.5.1.el6.x86_64/

Keepalived configuration

------------------------

Keepalived version : 1.2.13

Compiler : gcc

Compiler flags : -g -O2

Extra Lib : -lssl -lcrypto -lcrypt

Use IPVS Framework : Yes

IPVS sync daemon support : Yes

IPVS use libnl : No

fwmark socket support : Yes

Use VRRP Framework : Yes

Use VRRP VMAC : Yes

SNMP support : No

SHA1 support : No

Use Debug flags : No

# make

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

# 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 mysqld on

# chkconfig keepalived on

LVS安装

ipvsadm下载地址

需要安装以下软件包

# yum install -y libnl* popt*

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

LVS安装完成,查看当前LVS集群

# ipvsadm -L -n

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

-> RemoteAddress:Port Forward Weight ActiveConn InActConn

LVS+Keepalived配置

搭建MySQL主主复制

这里不再赘述,请参考MySQL复制

配置Keepalived

下面是LVS1节点(Keepalived主节点)上的Keepalived配置,LVS2类似

# vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {

router_id LVS1

}

vrrp_instance VI_1 {

state MASTER #指定instance初始状态,实际根据优先级决定.backup节点不一样

interface eth0 #虚拟IP所在网

virtual_router_id 51 #VRID,相同VRID为一个组,决定多播MAC地址

priority 100 #优先级,另一台改为90.backup节点不一样

advert_int 1 #检查间隔

authentication {

auth_type PASS #认证方式,可以是pass或ha

auth_pass 1111 #认证密码

}

virtual_ipaddress {

192.168.1.100 #VIP

}

}

virtual_server 192.168.1.100 3306 {

delay_loop 6 #服务轮询的时间间隔

lb_algo wrr #加权轮询调度,LVS调度算法 rr|wrr|lc|wlc|lblc|sh|sh

lb_kind DR #LVS集群模式 NAT|DR|TUN,其中DR模式要求负载均衡器网卡必须有一块与物理网卡在同一个网段

#nat_mask 255.255.255.0

persistence_timeout 50 #会话保持时间

protocol TCP #健康检查协议

## Real Server设置,3306就是MySQL连接端口

real_server 192.168.1.5 3306 {

weight 3 ##权重

TCP_CHECK {

connect_timeout 3

nb_get_retry 3

delay_before_retry 3

connect_port 3306

}

}

real_server 192.168.1.6 3306 {

weight 3

TCP_CHECK {

connect_timeout 3

nb_get_retry 3

delay_before_retry 3

connect_port 3306

}

}

}

配置LVS

编写LVS启动脚本/etc/init.d/realserver

#!/bin/sh

VIP=192.168.1.100

. /etc/rc.d/init.d/functions

case "$1" in

# 禁用本地的ARP请求、绑定本地回环地址

start)

/sbin/ifconfig lo down

/sbin/ifconfig lo up

echo "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

/sbin/sysctl -p >/dev/null 2>&1

/sbin/ifconfig lo:0 $VIP netmask 255.255.255.255 up #在回环地址上绑定VIP,设定掩码,与Direct Server(自身)上的IP保持通信

/sbin/route add -host $VIP dev lo:0

echo "LVS-DR real server starts successfully.n"

;;

stop)

/sbin/ifconfig lo:0 down

/sbin/route del $VIP >/dev/null 2>&1

echo "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

echo "LVS-DR real server stopped.n"

;;

status)

isLoOn=`/sbin/ifconfig lo:0 | grep "$VIP"`

isRoOn=`/bin/netstat -rn | grep "$VIP"`

if [ "$isLoON" == "" -a "$isRoOn" == "" ]; then

echo "LVS-DR real server has run yet."

else

echo "LVS-DR real server is running."

fi

exit 3

;;

*)

echo "Usage: $0 {start|stop|status}"

exit 1

esac

exit 0

将lvs脚本加入开机自启动

1

2# chmod +x /etc/init.d/realserver

# echo "/etc/init.d/realserver" >> /etc/rc.d/rc.local

分别启动LVS和keepalived

1

2# 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

# ipvsadm -ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

-> RemoteAddress:Port Forward Weight ActiveConn InActConn

TCP 192.168.1.100:3306 wrr persistent 50

-> 192.168.1.5:3306 Route 3 4 1

-> 192.168.1.6:3306 Route 3 0 2

此时LVS+Keepalived+MySQL主主复制已经搭建完成。

测试验证

功能性验证

关闭MySQL Server2

# service mysqld stop

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

2Sep 9 13:50:53 192.168.1.2 Keepalived_healthcheckers[18797]: TCP connection to [192.168.1.6]:3306 failed !!!

Sep 9 13:50:53 192.168.1.2 Keepalived_healthcheckers[18797]: Removing service [192.168.1.6]:3306 from VS [192.168.1.100]:3306

从新启动MySQL Server2后自动将故障节点自动加入LVS集群

2Sep 9 13:51:41 192.168.1.2 Keepalived_healthcheckers[18797]: TCP connection to [192.168.1.6]:3306 success.

Sep 9 13:51:41 192.168.1.2 Keepalived_healthcheckers[18797]: Adding service [192.168.1.6]:3306 to VS [192.168.1.100]: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

Sep 9 14:01:27 192.168.1.2 Keepalived[18796]: Stopping Keepalived v1.2.13 (09/09,2014)

Sep 9 14:01:27 192.168.1.2 Keepalived_healthcheckers[18797]: Removing service [192.168.1.5]:3306 from VS [192.168.1.100]:3306

Sep 9 14:01:27 192.168.1.2 Keepalived_healthcheckers[18797]: Removing service [192.168.1.6]:3306 from VS [192.168.1.100]:3306

Sep 9 14:01:27 192.168.1.2 Keepalived_vrrp[18799]: VRRP_Instance(VI_1) sending 0 priority

Sep 9 14:01:27 192.168.1.2 Keepalived_vrrp[18799]: VRRP_Instance(VI_1) removing protocol VIPs.

同时查看LVS2上日志,可以看到LVS2成为了Master,并接管了VIP

Sep 9 14:11:24 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Transition to MASTER STATE

Sep 9 14:11:25 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Entering MASTER STATE

Sep 9 14:11:25 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) setting protocol VIPs.

Sep 9 14:11:25 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.100

Sep 9 14:11:25 192.168.1.11 Keepalived_healthcheckers[7456]: Netlink reflector reports IP 192.168.1.100 added

Sep 9 14:11:25 192.168.1.11 avahi-daemon[1407]: Registering new address record for 192.168.1.100 on eth0.IPv4.

Sep 9 14:11:30 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.100

在LVS2上查看LVS集群状态,一切正常。

# ipvsadm -ln

IP Virtual Server version 1.2.1 (size=4096)

Prot LocalAddress:Port Scheduler Flags

-> RemoteAddress:Port Forward Weight ActiveConn InActConn

TCP 192.168.1.100:3306 wrr persistent 50

-> 192.168.1.5:3306 Route 3 2 0

-> 192.168.1.6:3306 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。

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。

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