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*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
需要安装以下软件包
1 | # 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
123456789101112131415161718 | # ./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.32-431.5.1.el6.x86_64/Keepalivedconfiguration------------------------Keepalivedversion :1.2.13Compiler :gccCompilerflags :-g-O2ExtraLib :-lssl-lcrypto-lcryptUseIPVSFramework :YesIPVSsyncdaemonsupport:YesIPVSuselibnl :Nofwmarksocketsupport :YesUseVRRPFramework :YesUseVRRPVMAC :YesSNMPsupport :NoSHA1support :NoUseDebugflags :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
123456 | # 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
需要安装以下软件包
1 | # yum install -y libnl* popt* |
查看是否加载lvs模块
1 | # modprobe -l |grep ipvs |
解压安装
123 | # 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
1234 | # ipvsadm -L -nIP 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
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051 | # vim /etc/keepalived/keepalived.conf !ConfigurationFileforkeepalived global_defs{ router_idLVS1} vrrp_instanceVI_1{ stateMASTER#指定instance初始状态,实际根据优先级决定.backup节点不一样 interfaceeth0#虚拟IP所在网 virtual_router_id51#VRID,相同VRID为一个组,决定多播MAC地址 priority100#优先级,另一台改为90.backup节点不一样 advert_int1 #检查间隔 authentication{ auth_typePASS #认证方式,可以是pass或ha auth_pass1111 #认证密码 } virtual_ipaddress{ 192.168.1.100 #VIP }} virtual_server192.168.1.1003306{ delay_loop6 #服务轮询的时间间隔 lb_algowrr #加权轮询调度,LVS调度算法 rr|wrr|lc|wlc|lblc|sh|sh lb_kindDR #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_timeout50 #会话保持时间 protocolTCP #健康检查协议 ## Real Server设置,3306就是MySQL连接端口 real_server192.168.1.53306{ weight3 ##权重 TCP_CHECK{ connect_timeout3 nb_get_retry3 delay_before_retry3 connect_port3306 } } real_server192.168.1.63306{ weight3 TCP_CHECK{ connect_timeout3 nb_get_retry3 delay_before_retry3 connect_port3306 } }} |
配置LVS
编写LVS启动脚本/etc/init.d/realserver
123456789101112131415161718192021222324252627282930313233343536373839404142 | #!/bin/shVIP=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 $VIP >/dev/null 2>&1 echo "1" >/proc/sys/net/ipv4/conf/lo/arp_ignore echo "2" >/proc/sys/net/ipv4/conf/lo/arp_announce echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore echo "2" >/proc/sys/net/ipv4/conf/all/arp_announceecho "LVS-DR real server stopped.n" ;;status) isLoOn=`/sbin/ifconfig lo:0 | grep "$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 1esacexit 0 |
将lvs脚本加入开机自启动
12 | # chmod +x /etc/init.d/realserver# echo "/etc/init.d/realserver" >> /etc/rc.d/rc.local |
分别启动LVS和keepalived
12 | # 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
1234567 | # ipvsadm -lnIPVirtualServerversion1.2.1(size=4096)ProtLocalAddress:PortSchedulerFlags ->RemoteAddress:Port ForwardWeightActiveConnInActConnTCP 192.168.1.100:3306wrrpersistent50 ->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
1 | # 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
12 | Sep 913:50:53192.168.1.2Keepalived_healthcheckers[18797]:TCPconnectionto[192.168.1.6]:3306failed!!!Sep 913:50:53192.168.1.2Keepalived_healthcheckers[18797]:Removingservice[192.168.1.6]:3306fromVS[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
12 | Sep 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
12345 | Sep 914:01:27192.168.1.2Keepalived[18796]:StoppingKeepalivedv1.2.13(09/09,2014)Sep 914:01:27192.168.1.2Keepalived_healthcheckers[18797]:Removingservice[192.168.1.5]:3306fromVS[192.168.1.100]:3306Sep 914:01:27192.168.1.2Keepalived_healthcheckers[18797]:Removingservice[192.168.1.6]:3306fromVS[192.168.1.100]:3306Sep 914:01:27192.168.1.2Keepalived_vrrp[18799]:VRRP_Instance(VI_1)sending0prioritySep 914:01:27192.168.1.2Keepalived_vrrp[18799]:VRRP_Instance(VI_1)removingprotocolVIPs. |
同时查看LVS2上日志,可以看到LVS2成为了Master,并接管了VIP
1234567 | Sep 9 14:11:24 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Transition to MASTER STATESep 9 14:11:25 192.168.1.11 Keepalived_vrrp[7457]: VRRP_Instance(VI_1) Entering MASTER STATESep 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 192.168.1.100Sep 9 14:11:25 192.168.1.11 Keepalived_healthcheckers[7456]: Netlink reflector reports IP 192.168.1.100 addedSep 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。
1234567 | # ipvsadm -lnIPVirtualServerversion1.2.1(size=4096)ProtLocalAddress:PortSchedulerFlags ->RemoteAddress:Port ForwardWeightActiveConnInActConnTCP 192.168.1.100:3306wrrpersistent50 ->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。