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 1
modprobe -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.conf
net.ipv4.ip_forward = 1 # 此参数改为1
sysctl -p # 使修改生效
安装依赖:
yum -y install openssl-devel
# 下载并安装keepalived
wget http://www.keepalived.org/software/keepalived-1.1.19.tar.gz
tar -zxvf keepalived-1.1.19.tar.gz
cd 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 keepalived
global_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 keepalived
global_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ip
VIP=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/functions
case $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 1
esac
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/sh
VIP=192.168.3.100
. /etc/rc.d/init.d/functions
case $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 1
esac
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/message
Mar 21 22:29:10 master kernel: device eth0 left promiscuous mode
Mar 21 22:29:10 master kernel: type=1700 audit(1332340150.598:12): dev=eth0 prom=0 old_prom=256 auid=4294967295 ses=4294967295
Apr 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 added
Apr 16 13:31:32 master Keepalived_healthcheckers: Registering Kernel netlink reflector
Apr 16 13:31:32 master Keepalived_healthcheckers: Registering Kernel netlink command channel
Apr 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 Bytes
Apr 16 13:31:32 master Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
Apr 16 13:31:32 master Keepalived: Starting Healthcheck child process, pid=5369
Apr 16 13:31:32 master Keepalived: Starting VRRP child process, pid=5370
Apr 16 13:31:32 master Keepalived_vrrp: Netlink reflector reports IP 192.168.3.101 added
Apr 16 13:31:32 master Keepalived_vrrp: Registering Kernel netlink reflector
Apr 16 13:31:32 master Keepalived_vrrp: Registering Kernel netlink command channel
Apr 16 13:31:32 master Keepalived_vrrp: Registering gratutious ARP shared channel
Apr 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 Bytes
Apr 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 STATE
Apr 16 13:31:34 master Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Apr 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 added
Apr 16 13:31:34 master Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.100
Apr 16 13:31:34 master Keepalived_vrrp: Netlink reflector reports IP 192.168.3.100 added
Apr 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 STATE
Apr 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 added
Apr 16 13:33:35 slave Keepalived_healthcheckers: Registering Kernel netlink reflector
Apr 16 13:33:35 slave Keepalived_healthcheckers: Registering Kernel netlink command channel
Apr 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 Bytes
Apr 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/message
Apr 16 13:39:44 slave Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Apr 16 13:39:45 slave Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Apr 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 192.168.3.100
Apr 16 13:39:45 slave Keepalived_vrrp: Netlink reflector reports IP 192.168.3.100 added
Apr 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):
ipvsadm
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 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.