lvs+keepalived实现高可用群集配置详解

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https://www.linuxzen.com/lvskeepalivedshi-xian-gao-ke-yong-qun-ji-pei-zhi-xiang-jie.html

lvs是一个开源的软件，由毕业于国防科技大学的章文嵩博士于1998年5月创立(中国人的项目)，可以实现LINUX平台下的简单负载均衡。LVS是Linux Virtual Server的缩写，意思是Linux虚拟服务器。本文将介绍lvs结合keepalived实现一个高科用的Linux群集系统.

lvs有三种工作模式NAT(地址转换),IP Tunneling(IP隧道)、Direct Routing(直接路由)。工作效率最低的是NAT模式,但NAT模式可以用于各种系统,各种环境的负载均衡,只需要一个公网ip即可实现 IP Tunneling模式调度器将连接分发到不同的后端real server,然后由real server处理请求直接相应给用户,大大提高了调度器的调度效率,后端real server没有物理位置和逻辑关系的限制,后端real server可以在Lan/Wlan,但是后端real server必须支持IP隧道协议. DR(Direct Routing)是效率最高的,与IP Tunneling类似,都是处理一般连接,将请求给后端real server,然后由real server处理请求直接相应给用户,Direct Routing与IP Tunneling相比，没有IP封装的开销，但由于采用物理层,所以DR模式的调度器和后端real server必须在一个物理网段里,中间不能过路由器(也就是一个交换机相连).

lvs支持8种不同的调度算法轮叫(rr)、加权轮叫(wrr)、最小连接(lc)、加权最小连接(wlc)、基于局部性最小连接(lblc)、带复制的基于局部性最少链接(lblcr)、目标地址散列(dh)和源地址散列(sh).

下面就介绍如何来安装和配置lvs+keepalived

本文使用环境: 操作系统:CentOS 5.5 32bit

主调度器:192.168.3.101/24

备调度器:192.168.3.102/24

后端real server: 192.168.3.3/24 |192.168.3.102/24(我们这里使用备用lvs作为一个测试

vip(virtual ip):192.168.3.100/24

lvs在2.6的内核中是默认支持的,所以我们就不需要在来安装,但是我们需要安装用户配置工具ipvsadm

yum -y install ipvsadm           # 分别在主从lvs上执行安装ipvsadm

我们查看lvs是否支持:

lsmod ¦ grep ip_vs          #ip_vs                  78081  1modprobe -l¦ grep ip_vs/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_dh.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_ftp.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_lblc.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_lblcr.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_lc.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_nq.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_rr.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_sed.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_sh.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_wlc.ko/lib/modules/2.6.18-194.el5/kernel/net/ipv4/ipvs/ip_vs_wrr.ko

本文介绍lvs的DR模式,首先部署keepalived.本博前面已经介绍如何来安装keepalived.这里就不在只简单的贴一下步骤:

在主备服务器上部署keepalived(因为前面已经rpm包安装了ipvsadm,所以就不需要重复安装):

vi /etc/sysctl.confnet.ipv4.ip_forward = 1 # 此参数改为1sysctl -p # 使修改生效

安装依赖:

yum  -y install openssl-devel# 下载并安装keepalivedwget http://www.keepalived.org/software/keepalived-1.1.19.tar.gztar -zxvf keepalived-1.1.19.tar.gzcd keepalived-1.1.19./configure --prefix=/ \            # 安装在默认位置(配置文件,二进制文件,启动脚本放到默认位置)--mandir=/usr/local/share/man/ \--with-kernel-dir=/usr/src/kernels/2.6.18-194.el5-i686/    # 需要内核的头文件make && make install

在主备lvs上安装keepalived完毕后我们先来配置主lvs上的keepalived: 编辑配置文件/etc/keepalived/keepalived.conf:

! Configuration File for keepalivedglobal_defs {   notification_email {    coldnight@linuxzen.com                                   # 发生故障时发送的邮箱   }   notification_email_from linuxzen@linuxzen.com             # 使用哪个邮箱发送   smtp_server linuxzen.com                                  # 发件服务器   smtp_connect_timeout 30   router_id LVS_DEVEL}vrrp_instance VI_1 {    state MASTER             # 标示为主lvs    interface eth0           # HA检测端口    virtual_router_id 51     # 主备的virtual_router_id 必须相同    priority 100             # 优先级,备lvs要比主lvs稍小    advert_int 1             # VRRP Multicast 广播周期秒数    authentication {         # 定义认证        auth_type PASS       # 认证方式为口令认证        auth_pass 1111       # 定义口令    }    virtual_ipaddress {      # 定义vip        192.168.3.100        # 多个vip可换行添加    }}virtual_server 192.168.3.100 80 {    delay_loop 6       # 每隔6秒查看realserver状态    lb_algo wlc        # 调度算法为加权最小连接数    lb_kind DR         # lvs工作模式为DR(直接路由)模式    nat_mask 255.255.255.0    persistence_timeout 50  # 同一IP 的连接50秒内被分配到同一台realserver(测试时建议改为0)    protocol TCP            # 用TCP监测realserver的状态    real_server 192.168.3.3 80 {       # 定义realserver        weight 3                       # 定义权重        TCP_CHECK {  # 注意TCP_CHECK和{之间的空格,如果没有的话只会添加第一个realserver            connect_timeout 3          # 三秒无响应超时            nb_get_retry 3            delay_before_retry 3            connect_port 80        }    }    real_server 192.168.3.102 80 {        weight 3        TCP_CHECK {            connect_timeout 3            nb_get_retry 3            delay_before_retry 3            connect_port 80        }    }}

配置备用lvs的keepalived,只需要将state MASTER 改为state BACKUP,降低priority 100 的值:

! Configuration File for keepalivedglobal_defs {   notification_email {    coldnight@linuxzen.com                               # 发生故障时发送的邮箱   }   notification_email_from linuxzen@linuxzen.com         # 使用哪个邮箱发送   smtp_server linuxzen.com                              # 发件服务器   smtp_connect_timeout 30   router_id LVS_DEVEL}vrrp_instance VI_1 {    state BACKUP              # 标示为备lvs    interface eth0            # HA检测端口    virtual_router_id 51      # 主备的virtual_router_id 必须相同    priority 99               # 优先级,备lvs要比主lvs稍小    advert_int 1              # VRRP Multicast 广播周期秒数    authentication {          # 定义认证        auth_type PASS        # 认证方式为口令认证        auth_pass 1111        # 定义口令    }    virtual_ipaddress {       # 定义vip        192.168.3.100         # 多个vip可换行添加    }}virtual_server 192.168.3.100 80 {    delay_loop 6      # 每隔6秒查看realserver状态    lb_algo wlc       # 调度算法为加权最小连接数    lb_kind DR        # lvs工作模式为DR(直接路由)模式    nat_mask 255.255.255.0    persistence_timeout 50  # 同一IP 的连接50秒内被分配到同一台realserver    protocol TCP            # 用TCP监测realserver的状态    real_server 192.168.3.3 80 {       # 定义realserver        weight 3                       # 定义权重        TCP_CHECK {    # 注意TCP_CHECK和{之间的空格,如果没有的话只会添加第一个realserver            connect_timeout 3          # 三秒无响应超时            nb_get_retry 3            delay_before_retry 3            connect_port 80        }    }    real_server 192.168.3.102 80 {        weight 3        TCP_CHECK {            connect_timeout 3            nb_get_retry 3            delay_before_retry 3            connect_port 80        }    }}

由于使用keepalived就不需要使用脚本来配置lvs调度器,但是这里我们还是会给出一个脚本内容,但我们不会用到这个脚本:lvs已经内置于内核,配置命令是ipvsadm,所以lvs的一些操作是通过ipvsadm来控制.下面我们就编写脚本来实现lvs的DR模式:

编写脚本lvsdr:

我们把lvsvi /etc/init.d/lvsdr添加如下内容

#!/bin/sh# 定义虚拟ipVIP=192.168.3.100# 定义realserver,并已逗号分开RIPS=192.168.3.3,192.168.3.102 #,192.168.3.5,192.168.3.6# 定义提供服务的端口SERVICE=80# 调用init.d脚本的标准库. /etc/rc.d/init.d/functionscase $1 in        start)        echo "Start LVS of DR Mode"        # lvs dr模式不需要路由转发,但是keepalived需要        #echo "0" > /proc/sys/net/ipv4/ip_forward        # 开启icmp包重定向        echo "1" > /proc/sys/net/ipv4/conf/all/send_redirects        echo "1" > /proc/sys/net/ipv4/conf/default/send_redirects        echo "1" > /proc/sys/net/ipv4/conf/eth0/send_redirects        # 绑定虚拟ip        ifconfig eth0:0 $VIP broadcast $VIP netmask 255.255.255.255 up        route add -host $VIP dev eth0:0        # 清除lvs规则        ipvsadm -C        # 添加一条虚拟服务器记录    # -p指定一定的时间内将相同的客户端分配到同一台后端服务器    # 用于解决session的问题,测试时或有别的解决方案时建议去掉        ipvsadm -A -t $VIP:$SERVICE -s wlc -p        # 添加真实服务器记录        for RIP in `echo $RIPS ¦sed  -e 's/,/\n/g'`        do                ipvsadm -a -t $VIP:$SERVICE -r $RIP:$SERVICE -g -w 1        done        # 设置tcp tcpfin  udp的超时连接值        ipvsadm --set 30 120 300        ipvsadm        ;;        stop)        echo "Stop LVS DR"        ifconfig eth0:0 down        ipvsadm -C        ;;        *)        echo "Usage:$0 {start ¦ stop}"        exit 1esac

编辑完毕保存退出,然后给这个脚本执行权限:

chmod +x /etc/init.d/lvsdr

然后就可以通过service命令来启动lvs dr模式

service lvsdr start

将这个脚本分别放到主备lvs的/etc/init.d/下,赋予执行权限. 我们真正需要的是realserver的脚本,下面我们来编写realserver脚本,同样放在/etc/init.d/下,编辑rs脚本:

vi /etc/init.d/lvsrs#!/bin/shVIP=192.168.3.100. /etc/rc.d/init.d/functionscase $1 in        start)        echo "lo:0 port starting"        # 为了相应lvs调度器转发过来的包,需在本地lo接口上绑定vip        ifconfig lo:0 $VIP broadcast $VIP netmask 255.255.255.255 up        # 限制arp请求        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        ;;        stop)        echo "lo:0 port closing"        ifconfig lo:0 down        echo "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 "Usage: $0 {start ¦ stop}"        exit 1esac

给脚本赋予执行权限

chmod +x /etc/init.d/lvsrs

并将这个脚本放到所有的realserver的/etc/init.d/下.下面开始测试:

先来确认下我们做的变动:主从lvs分别安装keepalived,并且在/etc/init.d/下添加了lvsdr脚本(不使用).

后端realserver分别在/etc/init.d/下添加了lvsrs脚本.我们先测试keepalived:

首先在主调度器上启动keepalived:

service keepalived start

查看日志文件:

tail -50 /var/log/messageMar 21 22:29:10 master kernel: device eth0 left promiscuous modeMar 21 22:29:10 master kernel: type=1700 audit(1332340150.598:12): dev=eth0 prom=0 old_prom=256 auid=4294967295 ses=4294967295Apr 16 13:31:32 master Keepalived: Starting Keepalived v1.1.19 (04/16,2012)Apr 16 13:31:32 master Keepalived_healthcheckers: Netlink reflector reports IP 192.168.3.101 addedApr 16 13:31:32 master Keepalived_healthcheckers: Registering Kernel netlink reflectorApr 16 13:31:32 master Keepalived_healthcheckers: Registering Kernel netlink command channelApr 16 13:31:32 master Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.Apr 16 13:31:32 master Keepalived_healthcheckers: Configuration is using : 8897 BytesApr 16 13:31:32 master Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...Apr 16 13:31:32 master Keepalived: Starting Healthcheck child process, pid=5369Apr 16 13:31:32 master Keepalived: Starting VRRP child process, pid=5370Apr 16 13:31:32 master Keepalived_vrrp: Netlink reflector reports IP 192.168.3.101 addedApr 16 13:31:32 master Keepalived_vrrp: Registering Kernel netlink reflectorApr 16 13:31:32 master Keepalived_vrrp: Registering Kernel netlink command channelApr 16 13:31:32 master Keepalived_vrrp: Registering gratutious ARP shared channelApr 16 13:31:32 master Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.Apr 16 13:31:32 master Keepalived_vrrp: Configuration is using : 36512 BytesApr 16 13:31:32 master Keepalived_vrrp: Using LinkWatch kernel netlink reflector...Apr 16 13:31:32 master Keepalived_vrrp: VRRP sockpool: [ifindex(2), proto(112), fd(10,11)]Apr 16 13:31:33 master Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATEApr 16 13:31:34 master Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATEApr 16 13:31:34 master Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.Apr 16 13:31:34 master Keepalived_healthcheckers: Netlink reflector reports IP 192.168.3.100 addedApr 16 13:31:34 master Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.100Apr 16 13:31:34 master Keepalived_vrrp: Netlink reflector reports IP 192.168.3.100 addedApr 16 13:31:39 master Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.100

然后在备用调度器上启动keepalived然后查看日志:

Apr 16 13:33:35 slave Keepalived_vrrp: VRRP_Instance(VI_1) Entering BACKUP STATEApr 16 13:33:35 slave Keepalived_vrrp: VRRP sockpool: [ifindex(2), proto(112), fd(11,12)]Apr 16 13:33:35 slave Keepalived_healthcheckers: Netlink reflector reports IP 192.168.3.102 addedApr 16 13:33:35 slave Keepalived_healthcheckers: Registering Kernel netlink reflectorApr 16 13:33:35 slave Keepalived_healthcheckers: Registering Kernel netlink command channelApr 16 13:33:35 slave Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.Apr 16 13:33:35 slave Keepalived_healthcheckers: Configuration is using : 8895 BytesApr 16 13:33:35 slave kernel: IPVS: [wlc] scheduler registered.Apr 16 13:33:35 slave Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...

在主调度器上执行

service keepalived stop

查看备用调度器日志:

tail -20 /var/log/messageApr 16 13:39:44 slave Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATEApr 16 13:39:45 slave Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATEApr 16 13:39:45 slave Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.Apr 16 13:39:45 slave Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.100Apr 16 13:39:45 slave Keepalived_vrrp: Netlink reflector reports IP 192.168.3.100 addedApr 16 13:39:45 slave Keepalived_healthcheckers: Netlink reflector reports IP 192.168.3.100 added

我们看到keepalived已经成功切换.

然后我们使用ipvsadm命令查看(在此之前要确认后端realserver已经启动了web服务):

ipvsadmIP Virtual Server version 1.2.1 (size=4096)Prot LocalAddress:Port Scheduler Flags  -> RemoteAddress:Port           Forward Weight ActiveConn InActConnTCP  192.168.3.100:http wlc  -> 192.168.3.3:http             Route   3      0          0  -> 192.168.3.102:http           Route   3      0          0

然后分别启动后端realserver的lvsrs服务:

servie lvsrs start

然后浏览器访问192.168.3.100,如果keepalived的persistence_timeout参数值为0,而且两个后端realserver是不同的内容,刷新就可以看到两个不同的页面交替.

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